[top]
000
FXUS63 KILX 230517
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1117 PM CST SUN NOV 22 2009
.DISCUSSION...
ISSUED 857 PM CST SUN NOV 22 2009
TEMPS ARE FALLING LITTLE FURTHER AND SOME SITES ALREADY CLOSE TO
FORECASTED MINS...MAINLY IN THE NORTHEAST. HIGH CLOUDS CONTINUE
OVER THE WEST AND EASTERN PARTS OF THE CWA SO THIS SHOULD CAUSE
TEMPS TO BECOME STEADY OVERNIGHT. SO WILL BE MAKING SOME
ADJUSTMENTS TO TEMP GRIDS TONIGHT. NOT SURE YET IF IT WILL AFFECT
TEXT PRODUCT...BUT IF DOES...SHOULD ONLY AFFECT EASTERN AND
NORTHEAST GROUPS.
AUTEN
&&
.AVIATION...
ISSUED 1117 PM CST SUN NOV 22 2009
VFR CONDITIONS WILL PREVAIL THROUGH MOST OF THE TAF TIME PERIOD.
SKIES WILL BE BROKEN WITH CIGS AT AROUND 15KFT THROUGH TOMORROW
MORNING. THEN SKIES CLEAR FOR REMAINDER OF THE PERIOD.
HOWEVER...COULD BE A LITTLE BIT OF FOG TOMORROW NIGHT BUT ONLY
AROUND 4 MILES...AS RETURN FLOW BEGINS TO SETUP AHEAD OF THE NEXT
SYSTEM. WINDS WILL REMAIN EAST TO SOUTHEAST THROUGH THE PERIOD.
AUTEN
&&
.PREV DISCUSSION...
ISSUED 309 PM CST SUN NOV 22 2009
A PLEASANT FALL DAY IS UNFOLDING ACROSS CENTRAL AND SOUTHEAST
ILLINOIS...COURTESY OF A LARGE AREA OF HIGH PRESSURE CENTERED OVER
NEW ENGLAND. ONE MORE PRETTY NICE DAY IS ON TAP UNTIL SLOW MOVING
STORM SYSTEM ARRIVES FOR TUESDAY AND LINGERS IN THE AREA THROUGH
THANKSGIVING. THIS SLOW MOVING STORM SYSTEM...AND THE ASSOCIATED
PRECIPITATION THREAT AND IMPACT ON TEMPERATURES...IS OUR PRIMARY
FORECAST CONCERN TODAY.
12Z MODELS IN REASONABLE AGREEMENT THROUGH THE SHORT TERM.
HOWEVER...THEY ARE TRENDING SLOWER WITH OUR APPROACHING STORM
SYSTEM. HAVE TRENDED THE FORECAST TOWARD THE MIDDLE OF THE MODEL
ENVELOPE...WHICH IS QUICKER THAN THE NAM....BUT SLOWER THAN THE
GFS.
SHORT TERM...TONIGHT THROUGH WEDNESDAY...OUR STORM SYSTEM IS
ALREADY BEGINNING TO DEVELOP OVER THE CENTRAL PLAINS...AS
EVIDENCED BY THE LOW PRESSURE CENTER STARTING TO DEVELOP OVER
KANSAS. HOWEVER...IT WILL NOT REALLY DEEPEN OR START MOVING OUR
DIRECTION UNTIL IT INTERACTS WITH THE VIGOROUS UPPER WAVE
CURRENTLY DIVING THROUGH THE PACIFIC NORTHWEST. IN THE MEANTIME...
QUIET AND MILD LATE NOVEMBER CONDITIONS WILL PERSIST INTO MONDAY
NIGHT AS RETURN FLOW INCREASES ON THE BACK SIDE OF THE DEPARTING
AREA OF HIGH PRESSURE. THE DIURNAL TEMPERATURE RANGE MAY BE A BIT
SMALLER THROUGH MONDAY NIGHT THAN THE PAST FEW DAYS AS THE SYSTEM
BEGINS TO APPROACH AND CLOUD COVER INCREASES.
THE APPROACHING STORM AND TRAILING FRONTAL BOUNDARY IS STILL
EXPECTED TO MOVE THROUGH THE REGION ON TUESDAY...BUT THE FRONTAL
SPEED HAS SLIPPED BY ABOUT 6 HOURS. SO...AN 18Z TUE-06Z WED
PASSAGE LOOKS MORE LIKELY NOW THAN THE PREVIOUSLY EXPECTED 12Z
TUE-00Z WED PASSAGE. THE MAIN SURFACE LOW WILL LIFT INTO THE GREAT
LAKES TUESDAY NIGHT...WITH THE TRAILING COLD FRONT EXPECTED TO
CLEAR THE FORECAST AREA BY AROUND 06Z WEDNESDAY. THIS SYSTEM
SHOULD BE PRETTY DYNAMIC...THOUGH ALREADY OCCLUDED BY THE TIME IT
GETS HERE...WITH DECENT JET FORCING PROGGED OVER THE FORECAST AREA
ON TUESDAY COUPLED WITH THE SURFACE FROPA. HAVE KEPT LIKELY RAIN
CHANCES IN THE WESTERN HALF OF THE FORECAST AREA FOR TUESDAY...WITH
THE EASTERN HALF PROBABLY NEEDING A BUMP ONCE THE TIMING IS MORE
FIRM. HOWEVER...IT IS HARD TO JUSTIFY LIKELY POPS IN THE EAST AT
THIS TIME AS THE FROPA STILL APPEARS POSSIBLE IN MORE THAN ONE
FORECAST PERIOD.
ONCE THE FRONT CLEARS THE FORECAST AREA TO THE EAST...THERE SHOULD
BE A LULL IN THE PRECIPITATION THREAT. WHILE WRAP AROUND
PRECIPITATION IS POSSIBLE WEDNESDAY...THE BULK OF IT SHOULD HOLD OFF
UNTIL THE EXTENDED RANGE OF THE FORECAST PERIOD. THE SLOWER
PROGRESSION OF THE SYSTEM AND ASSOCIATED ARRIVAL OF COLDER AIR
SHOULD KEEP ANY PRECIPITATION FALLING AS RAIN THROUGH WEDNESDAY.
LONG TERM...WEDNESDAY NIGHT THROUGH SUNDAY...MODELS/ENSEMBLES
INITIALLY IN FAIRLY GOOD AGREEMENT WITH RESPECT TO FEATURES
EXPECTED TO IMPACT FORECAST AREA. HOWEVER...SPREAD INCREASES
SIGNIFICANTLY FROM FRIDAY TO THE END OF THE PERIOD.
UNFORTUNATELY...ONE ITEM THAT HAS DEVELOPED SINCE YESTERDAY IS
THAT IT LOOKS INCREASINGLY LIKELY THAT PRECIPITATION...MOSTLY
SNOW...IS POSSIBLE ON THANKSGIVING. THE SURFACE LOW THAT BROUGHT
THE RAINS ON TUESDAY WILL STILL BE OVER THE GREAT LAKES AT THE
START OF THE PERIOD. A STRONG UPPER WAVE WILL DIVE DOWN THE
BACKSIDE OF THIS VERTICALLY STACKED SYSTEM...LIKELY PRODUCING A
ROUND OF PRECIPITATION LATE WEDNESDAY NIGHT INTO THANKSGIVING DAY.
SOUNDING PROFILES/THICKNESS SCHEMES SUGGEST THAT ALL THE WARM AIR
WILL BE NEAR SURFACE BASED WHEN THIS PRECIPITATION WOULD FALL. SO
THE PRECIPITATION WILL BE FALLING AS SNOW...AND IT APPEARS THAT
THE ABOVE FREEZING NEAR SURFACE LAYER WILL BE TOO SHALLOW TO MELT
THE SNOW BEFORE IT REACHES THE GROUND. HOWEVER...AT THIS POINT...
LITTLE OR NO ACCUMULATION IS EXPECTED WITH THE SNOW. UPPER/SURFACE
RIDGING START TO BUILD IN FRIDAY INTO SATURDAY ENDING THE
PRECIPITATION AND ALLOWING TEMPERATURES TO MODERATE A BIT. THE
ARRIVAL OF THE NEXT WEATHER SYSTEM IS MUCH LESS CLEAR AT THIS
TIME. THE GFS SOLUTIONS TEND TO DEVELOP A MORE PHASED DEEP TROF
OVER EASTERN NORTH AMERICA...WHILE THE ECMWF SPLITS THE FLOW AND
CUTS OFF A LOW OVER THE SOUTHWEST UNITED STATES. THIS RESULTS IN
THE GFS BEING QUICKER AND STRONGER WITH THE NEXT SYSTEM BY LATE IN
THE WEEKEND. WILL CONTINUE TO SIDE WITH THE MORE CONSISTENT ECMWF
AND LEAVE THE END OF THE WEEKEND DRY AT THIS TIME.
BAK
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
[top]
000
FXUS63 KLOT 230420
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1020 PM CST SUN NOV 22 2009
.DISCUSSION...
243 PM CST
WITH CLOUD COVER PASSING TO THE WEST OF NORTHERN IL TONIGHT...PATCHY
FOG TO BE A CONCERN OVERNIGHT. VSBYS NOT DENSE THIS MRNG BUT LIKELY
TO BE SO OVERNIGHT IAW MOS OUTPUT. WILL AGAIN LEAVE EVENING OR MID
SHIFT WITH METWATCH RESPONSIBILITY ON WHETHER DENSE FOG ADVISORY IS
TO BE REQUIRED. WITH UPR RIDGE RETREATING TO THE NORTHEAST
TONIGHT...ILLINOIS LIKELY TO SEE WAA CI AND AC MOVING IN EARLY
MONDAY. CLOUDS SHUD INCREASE THRU THE DAY AND BECOME RATHER CLOUDY
OVERNIGHT MON NGT AS NEXT STORM SYSTEM DEEPENS OVER THE NRN ROCKIES
AND PLAINS. THIS SYSTEM CONTINUES TO DEEPEN AS IT MOVES ACROSS
THE PLAINS AND INTO THE MS VLY ON TUESDAY.
MODELS STILL TRENDING TOWARD OCCLUDING THIS SYSTEM FROM THE MID
AND UPR MS VLY TO THE GREAT LAKES TUES INTO TUES NGT. WHILE
CONCESSIONS AMONG MODELS HAVE BROUGHT THEM CLOSER ON STORM
TRACKING... TIMING IS STILL A BIT OFF. GFS IS MUCH QUICKER WHILE
ECMWF IS SLOWEST. NAM HOWEVER TAKES A MIDDLE GROUND AND WUD MAKE A
DECENT BLEND AMONG THEM. THIS COMPROMISE MAY BRING IN RAIN ON
TUESDAY BUT WUD LIKELY BACK OFF UNTIL THE AFTN. TENDENCY THEN MAY BE
TO PUSH BACK ONSET OF RAIN INTO THE EVENING. NEXT MODEL RUN OR TWO
SHUD PROBABLY RESOLVE THAT ISSUE.
ALL MODELS STILL RESOLVING TWO DISTINCT CLOSED UPR TROFS WITH THIS
HOLIDAY EVENT. THE FIRST TROF...OR UPR LOW...WILL SWING THRU
WEDNESDAY AND BRING COLDER AIR INTO THE MS VLY IN THE AFTN. WEAK UPR
RIDGING SEPARATES THIS FIRST TROF AND THE SECONDARY UPR TROF THAT
DROPS SE FROM MANITOBA TO NRN IL WED NGT. THE SECOND SHOT OF CAA
FOLLOWING THIS TROF IS MORE SIGNIFICANT. ANY RESIDUAL SHOWERS SHUD
START MIXING WITH SNOW WED EVENING AND CHANGING OVER TO ALL LIGHT
SNOW LATE WED NGT. POST LOW CYCLONIC FLOW IN THE COLD WRAPAROUND
WILL MAINTAIN A LGT SNOW OR FLURRY THREAT THRU THURSDAY BEFORE UPR
RIDGING WORKS IN FRIDAY AND ENDS ANYMORE PCPN.
UPPER RIDGING WORKING ACROSS THE MS VLY SAT SHUD RETURN SW FLOW TO
THE MIDWEST BY SUNDAY. LONG TERM PATTERNS ARE RATHER SUSPECT BUT
SUGGEST ANOTHER SYSTEM CENTERED OVER THE NRN PLAINS SWINGING ANOTHER
COLD FRONT ACROSS THE MS VLY LATE SAT INTO SUNDAY WITH RAIN CHANGING
TO SNOW SUNDAY AFTN. LOW CONFIDENCE BASED ON TIMING DISCONTINUITIES
SUGGESTS LEAVING OUT ANY MENTION OF IT FOR NOW.
RLB
&&
.AVIATION...
0600 UTC TAFS...A LARGE HIGH OVER NORTHERN NEW BRUNSWICK WILL
EXTEND WEST TO NORTHERN ILLINOIS OVERNIGHT. THE HIGH WILL MOVE
EAST AND WILL BE OFF THE COAST OF NOVA SCOTIA BY MONDAY EVENING.
THERE WILL BE A SOUTHEAST WIND OF 5 TO 8 KNOTS TONIGHT. THERE IS
MORE MOISTURE IN THE ATMOSPHERE THAN LAST NIGHT. THIS IS SEEN BY
THE HIGHER SURFACE DEWPOINTS TONIGHT. WE WILL FORECAST SOME FOG
WITH THE VISIBILITY AROUND 3 MILES AFTER 10 UTC. ROCKFORD AND
DUPAGE AIRPORTS MAY HAVE THE VISIBILITY AS LOW AS 1 TO 2 MILES
AFTER 11 UTC. SOME HIGH AND MIDDLE LEVEL CLOUDS WILL MOVE OVER
NORTHEAST AND NORTH CENTRAL ILLINOIS THROUGH THIS EARLY MORNING.
&&
.MARINE...
107 PM CST
A BROAD RIDGE OF HIGH PRESSURE EAST OF THE GREAT LAKES
WILL CONTINUE TO SLOWLY DRIFT EASTWARD. MEANWHILE...AN AREA OF LOW
PRESSURE WILL DEVELOP ACROSS THE SOUTHERN PLAINS TONIGHT...REACHING
WESTERN IOWA BY TUESDAY MORNING...AND NORTHERN ILLINOIS TUESDAY
NIGHT. THIS LOW WILL THEN MOVE ACROSS SOUTHERN LAKE MICHIGAN EARLY
WEDNESDAY MORNING.
THIS WILL PROMOTE A GENERALLY LIGHT SOUTHEAST WIND FLOW ACROSS
LAKE MICHIGAN THROUGH TUESDAY.
MERZLOCK
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&
$$
000
FXUS63 KILX 230257
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
857 PM CST SUN NOV 22 2009
.DISCUSSION...
ISSUED 857 PM CST SUN NOV 22 2009
TEMPS ARE FALLING LITTLE FURTHER AND SOME SITES ALREADY CLOSE TO
FORECASTED MINS...MAINLY IN THE NORTHEAST. HIGH CLOUDS CONTINUE
OVER THE WEST AND EASTERN PARTS OF THE CWA SO THIS SHOULD CAUSE
TEMPS TO BECOME STEADY OVERNIGHT. SO WILL BE MAKING SOME
ADJUSTMENTS TO TEMP GRIDS TONIGHT. NOT SURE YET IF IT WILL AFFECT
TEXT PRODUCT...BUT IF DOES...SHOULD ONLY AFFECT EASTERN AND
NORTHEAST GROUPS.
AUTEN
&&
.AVIATION...
ISSUED 527 PM CST SUN NOV 22 2009
VFR CONDITIONS WILL CONTINUE TONIGHT BUT THEN LIGHT FOG WILL
DEVELOP AT ALL SITES AROUND 06Z LIKE IT DID LAST NIGHT. LIGHT FOG
WILL BURN OFF IN THE MORNING FOLLOWED BY A MID DECK ADVECTING INTO
THE AREA. PIA...BMI AND SPI COULD SEE SOME LOWER SC CLOUDS AT
3.5KFT WHILE DEC AND CMI WILL JUST SEE A MID DECK TOMORROW. LIGHT
EAST WINDS WILL BECOME SOUTHEAST TOMORROW AND CONTINUE INTO THE AFTERNOON.
AUTEN
&&
.PREV DISCUSSION...
ISSUED 309 PM CST SUN NOV 22 2009
A PLEASANT FALL DAY IS UNFOLDING ACROSS CENTRAL AND SOUTHEAST
ILLINOIS...COURTESY OF A LARGE AREA OF HIGH PRESSURE CENTERED OVER
NEW ENGLAND. ONE MORE PRETTY NICE DAY IS ON TAP UNTIL SLOW MOVING
STORM SYSTEM ARRIVES FOR TUESDAY AND LINGERS IN THE AREA THROUGH
THANKSGIVING. THIS SLOW MOVING STORM SYSTEM...AND THE ASSOCIATED
PRECIPITATION THREAT AND IMPACT ON TEMPERATURES...IS OUR PRIMARY
FORECAST CONCERN TODAY.
12Z MODELS IN REASONABLE AGREEMENT THROUGH THE SHORT TERM.
HOWEVER...THEY ARE TRENDING SLOWER WITH OUR APPROACHING STORM
SYSTEM. HAVE TRENDED THE FORECAST TOWARD THE MIDDLE OF THE MODEL
ENVELOPE...WHICH IS QUICKER THAN THE NAM....BUT SLOWER THAN THE
GFS.
SHORT TERM...TONIGHT THROUGH WEDNESDAY...OUR STORM SYSTEM IS
ALREADY BEGINNING TO DEVELOP OVER THE CENTRAL PLAINS...AS
EVIDENCED BY THE LOW PRESSURE CENTER STARTING TO DEVELOP OVER
KANSAS. HOWEVER...IT WILL NOT REALLY DEEPEN OR START MOVING OUR
DIRECTION UNTIL IT INTERACTS WITH THE VIGOROUS UPPER WAVE
CURRENTLY DIVING THROUGH THE PACIFIC NORTHWEST. IN THE MEANTIME...
QUIET AND MILD LATE NOVEMBER CONDITIONS WILL PERSIST INTO MONDAY
NIGHT AS RETURN FLOW INCREASES ON THE BACK SIDE OF THE DEPARTING
AREA OF HIGH PRESSURE. THE DIURNAL TEMPERATURE RANGE MAY BE A BIT
SMALLER THROUGH MONDAY NIGHT THAN THE PAST FEW DAYS AS THE SYSTEM
BEGINS TO APPROACH AND CLOUD COVER INCREASES.
THE APPROACHING STORM AND TRAILING FRONTAL BOUNDARY IS STILL
EXPECTED TO MOVE THROUGH THE REGION ON TUESDAY...BUT THE FRONTAL
SPEED HAS SLIPPED BY ABOUT 6 HOURS. SO...AN 18Z TUE-06Z WED
PASSAGE LOOKS MORE LIKELY NOW THAN THE PREVIOUSLY EXPECTED 12Z
TUE-00Z WED PASSAGE. THE MAIN SURFACE LOW WILL LIFT INTO THE GREAT
LAKES TUESDAY NIGHT...WITH THE TRAILING COLD FRONT EXPECTED TO
CLEAR THE FORECAST AREA BY AROUND 06Z WEDNESDAY. THIS SYSTEM
SHOULD BE PRETTY DYNAMIC...THOUGH ALREADY OCCLUDED BY THE TIME IT
GETS HERE...WITH DECENT JET FORCING PROGGED OVER THE FORECAST AREA
ON TUESDAY COUPLED WITH THE SURFACE FROPA. HAVE KEPT LIKELY RAIN
CHANCES IN THE WESTERN HALF OF THE FORECAST AREA FOR TUESDAY...WITH
THE EASTERN HALF PROBABLY NEEDING A BUMP ONCE THE TIMING IS MORE
FIRM. HOWEVER...IT IS HARD TO JUSTIFY LIKELY POPS IN THE EAST AT
THIS TIME AS THE FROPA STILL APPEARS POSSIBLE IN MORE THAN ONE
FORECAST PERIOD.
ONCE THE FRONT CLEARS THE FORECAST AREA TO THE EAST...THERE SHOULD
BE A LULL IN THE PRECIPITATION THREAT. WHILE WRAP AROUND
PRECIPITATION IS POSSIBLE WEDNESDAY...THE BULK OF IT SHOULD HOLD OFF
UNTIL THE EXTENDED RANGE OF THE FORECAST PERIOD. THE SLOWER
PROGRESSION OF THE SYSTEM AND ASSOCIATED ARRIVAL OF COLDER AIR
SHOULD KEEP ANY PRECIPITATION FALLING AS RAIN THROUGH WEDNESDAY.
LONG TERM...WEDNESDAY NIGHT THROUGH SUNDAY...MODELS/ENSEMBLES
INITIALLY IN FAIRLY GOOD AGREEMENT WITH RESPECT TO FEATURES
EXPECTED TO IMPACT FORECAST AREA. HOWEVER...SPREAD INCREASES
SIGNIFICANTLY FROM FRIDAY TO THE END OF THE PERIOD.
UNFORTUNATELY...ONE ITEM THAT HAS DEVELOPED SINCE YESTERDAY IS
THAT IT LOOKS INCREASINGLY LIKELY THAT PRECIPITATION...MOSTLY
SNOW...IS POSSIBLE ON THANKSGIVING. THE SURFACE LOW THAT BROUGHT
THE RAINS ON TUESDAY WILL STILL BE OVER THE GREAT LAKES AT THE
START OF THE PERIOD. A STRONG UPPER WAVE WILL DIVE DOWN THE
BACKSIDE OF THIS VERTICALLY STACKED SYSTEM...LIKELY PRODUCING A
ROUND OF PRECIPITATION LATE WEDNESDAY NIGHT INTO THANKSGIVING DAY.
SOUNDING PROFILES/THICKNESS SCHEMES SUGGEST THAT ALL THE WARM AIR
WILL BE NEAR SURFACE BASED WHEN THIS PRECIPITATION WOULD FALL. SO
THE PRECIPITATION WILL BE FALLING AS SNOW...AND IT APPEARS THAT
THE ABOVE FREEZING NEAR SURFACE LAYER WILL BE TOO SHALLOW TO MELT
THE SNOW BEFORE IT REACHES THE GROUND. HOWEVER...AT THIS POINT...
LITTLE OR NO ACCUMULATION IS EXPECTED WITH THE SNOW. UPPER/SURFACE
RIDGING START TO BUILD IN FRIDAY INTO SATURDAY ENDING THE
PRECIPITATION AND ALLOWING TEMPERATURES TO MODERATE A BIT. THE
ARRIVAL OF THE NEXT WEATHER SYSTEM IS MUCH LESS CLEAR AT THIS
TIME. THE GFS SOLUTIONS TEND TO DEVELOP A MORE PHASED DEEP TROF
OVER EASTERN NORTH AMERICA...WHILE THE ECMWF SPLITS THE FLOW AND
CUTS OFF A LOW OVER THE SOUTHWEST UNITED STATES. THIS RESULTS IN
THE GFS BEING QUICKER AND STRONGER WITH THE NEXT SYSTEM BY LATE IN
THE WEEKEND. WILL CONTINUE TO SIDE WITH THE MORE CONSISTENT ECMWF
AND LEAVE THE END OF THE WEEKEND DRY AT THIS TIME.
BAK
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
000
FXUS63 KLOT 230026
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
626 PM CST SUN NOV 22 2009
.DISCUSSION...
243 PM CST
WITH CLOUD COVER PASSING TO THE WEST OF NORTHERN IL TONIGHT...PATCHY
FOG TO BE A CONCERN OVERNIGHT. VSBYS NOT DENSE THIS MRNG BUT LIKELY
TO BE SO OVERNIGHT IAW MOS OUTPUT. WILL AGAIN LEAVE EVENING OR MID
SHIFT WITH METWATCH RESPONSIBILITY ON WHETHER DENSE FOG ADVISORY IS
TO BE REQUIRED. WITH UPR RIDGE RETREATING TO THE NORTHEAST
TONIGHT...ILLINOIS LIKELY TO SEE WAA CI AND AC MOVING IN EARLY
MONDAY. CLOUDS SHUD INCREASE THRU THE DAY AND BECOME RATHER CLOUDY
OVERNIGHT MON NGT AS NEXT STORM SYSTEM DEEPENS OVER THE NRN ROCKIES
AND PLAINS. THIS SYSTEM CONTINUES TO DEEPEN AS IT MOVES ACROSS
THE PLAINS AND INTO THE MS VLY ON TUESDAY.
MODELS STILL TRENDING TOWARD OCCLUDING THIS SYSTEM FROM THE MID
AND UPR MS VLY TO THE GREAT LAKES TUES INTO TUES NGT. WHILE
CONCESSIONS AMONG MODELS HAVE BROUGHT THEM CLOSER ON STORM
TRACKING... TIMING IS STILL A BIT OFF. GFS IS MUCH QUICKER WHILE
ECMWF IS SLOWEST. NAM HOWEVER TAKES A MIDDLE GROUND AND WUD MAKE A
DECENT BLEND AMONG THEM. THIS COMPROMISE MAY BRING IN RAIN ON
TUESDAY BUT WUD LIKELY BACK OFF UNTIL THE AFTN. TENDENCY THEN MAY BE
TO PUSH BACK ONSET OF RAIN INTO THE EVENING. NEXT MODEL RUN OR TWO
SHUD PROBABLY RESOLVE THAT ISSUE.
ALL MODELS STILL RESOLVING TWO DISTINCT CLOSED UPR TROFS WITH THIS
HOLIDAY EVENT. THE FIRST TROF...OR UPR LOW...WILL SWING THRU
WEDNESDAY AND BRING COLDER AIR INTO THE MS VLY IN THE AFTN. WEAK UPR
RIDGING SEPARATES THIS FIRST TROF AND THE SECONDARY UPR TROF THAT
DROPS SE FROM MANITOBA TO NRN IL WED NGT. THE SECOND SHOT OF CAA
FOLLOWING THIS TROF IS MORE SIGNIFICANT. ANY RESIDUAL SHOWERS SHUD
START MIXING WITH SNOW WED EVENING AND CHANGING OVER TO ALL LIGHT
SNOW LATE WED NGT. POST LOW CYCLONIC FLOW IN THE COLD WRAPAROUND
WILL MAINTAIN A LGT SNOW OR FLURRY THREAT THRU THURSDAY BEFORE UPR
RIDGING WORKS IN FRIDAY AND ENDS ANYMORE PCPN.
UPPER RIDGING WORKING ACROSS THE MS VLY SAT SHUD RETURN SW FLOW TO
THE MIDWEST BY SUNDAY. LONG TERM PATTERNS ARE RATHER SUSPECT BUT
SUGGEST ANOTHER SYSTEM CENTERED OVER THE NRN PLAINS SWINGING ANOTHER
COLD FRONT ACROSS THE MS VLY LATE SAT INTO SUNDAY WITH RAIN CHANGING
TO SNOW SUNDAY AFTN. LOW CONFIDENCE BASED ON TIMING DISCONTINUITIES
SUGGESTS LEAVING OUT ANY MENTION OF IT FOR NOW.
RLB
&&
.AVIATION...
0000 UTC TAFS...A LARGE HIGH OVER NORTHERN NEW BRUNSWICK WILL
EXTEND WEST TO NORTHERN ILLINOIS OVERNIGHT. THE HIGH WILL MOVE
EAST AND WILL BE OFF THE COAST OF NOVA SCOTIA BY MONDAY EVENING.
THERE WILL BE A SOUTHEAST WIND OF 5 TO 8 KNOTS TONIGHT. THERE IS
MORE MOISTURE IN THE ATMOSPHERE THAN LAST NIGHT. THIS IS SEEN BY
THE HIGHER SURFACE DEWPOINTS TONIGHT. WE WILL FORECAST SOME FOG
WITH THE VISIBILITY AROUND 3 MILES AFTER 10 UTC. ROCKFORD AND
DUPAGE AIRPORTS MAY HAVE THE VISIBILITY AS LOW AS 1 TO 2 MILES
AFTER 11 UTC. SOME CLOUDS AT 10000 TO 11000 FEET MAY MOVE OVER
NORTHEAST AND NORTH CENTRAL ILLINOIS LATE TONIGHT AND MONDAY.
&&
.MARINE...
107 PM CST
A BROAD RIDGE OF HIGH PRESSURE EAST OF THE GREAT LAKES
WILL CONTINUE TO SLOWLY DRIFT EASTWARD. MEANWHILE...AN AREA OF LOW
PRESSURE WILL DEVELOP ACROSS THE SOUTHERN PLAINS TONIGHT...REACHING
WESTERN IOWA BY TUESDAY MORNING...AND NORTHERN ILLINOIS TUESDAY
NIGHT. THIS LOW WILL THEN MOVE ACROSS SOUTHERN LAKE MICHIGAN EARLY
WEDNESDAY MORNING.
THIS WILL PROMOTE A GENERALLY LIGHT SOUTHEAST WIND FLOW ACROSS
LAKE MICHIGAN THROUGH TUESDAY.
MERZLOCK
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&
$$
000
FXUS63 KILX 222327
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
527 PM CST SUN NOV 22 2009
.DISCUSSION...
ISSUED 309 PM CST SUN NOV 22 2009
A PLEASANT FALL DAY IS UNFOLDING ACROSS CENTRAL AND SOUTHEAST
ILLINOIS...COURTESY OF A LARGE AREA OF HIGH PRESSURE CENTERED OVER
NEW ENGLAND. ONE MORE PRETTY NICE DAY IS ON TAP UNTIL SLOW MOVING
STORM SYSTEM ARRIVES FOR TUESDAY AND LINGERS IN THE AREA THROUGH
THANKSGIVING. THIS SLOW MOVING STORM SYSTEM...AND THE ASSOCIATED
PRECIPITATION THREAT AND IMPACT ON TEMPERATURES...IS OUR PRIMARY
FORECAST CONCERN TODAY.
12Z MODELS IN REASONABLE AGREEMENT THROUGH THE SHORT TERM.
HOWEVER...THEY ARE TRENDING SLOWER WITH OUR APPROACHING STORM
SYSTEM. HAVE TRENDED THE FORECAST TOWARD THE MIDDLE OF THE MODEL
ENVELOPE...WHICH IS QUICKER THAN THE NAM....BUT SLOWER THAN THE
GFS.
SHORT TERM...TONIGHT THROUGH WEDNESDAY...OUR STORM SYSTEM IS
ALREADY BEGINNING TO DEVELOP OVER THE CENTRAL PLAINS...AS
EVIDENCED BY THE LOW PRESSURE CENTER STARTING TO DEVELOP OVER
KANSAS. HOWEVER...IT WILL NOT REALLY DEEPEN OR START MOVING OUR
DIRECTION UNTIL IT INTERACTS WITH THE VIGOROUS UPPER WAVE
CURRENTLY DIVING THROUGH THE PACIFIC NORTHWEST. IN THE MEANTIME...
QUIET AND MILD LATE NOVEMBER CONDITIONS WILL PERSIST INTO MONDAY
NIGHT AS RETURN FLOW INCREASES ON THE BACK SIDE OF THE DEPARTING
AREA OF HIGH PRESSURE. THE DIURNAL TEMPERATURE RANGE MAY BE A BIT
SMALLER THROUGH MONDAY NIGHT THAN THE PAST FEW DAYS AS THE SYSTEM
BEGINS TO APPROACH AND CLOUD COVER INCREASES.
THE APPROACHING STORM AND TRAILING FRONTAL BOUNDARY IS STILL
EXPECTED TO MOVE THROUGH THE REGION ON TUESDAY...BUT THE FRONTAL
SPEED HAS SLIPPED BY ABOUT 6 HOURS. SO...AN 18Z TUE-06Z WED
PASSAGE LOOKS MORE LIKELY NOW THAN THE PREVIOUSLY EXPECTED 12Z
TUE-00Z WED PASSAGE. THE MAIN SURFACE LOW WILL LIFT INTO THE GREAT
LAKES TUESDAY NIGHT...WITH THE TRAILING COLD FRONT EXPECTED TO
CLEAR THE FORECAST AREA BY AROUND 06Z WEDNESDAY. THIS SYSTEM
SHOULD BE PRETTY DYNAMIC...THOUGH ALREADY OCCLUDED BY THE TIME IT
GETS HERE...WITH DECENT JET FORCING PROGGED OVER THE FORECAST AREA
ON TUESDAY COUPLED WITH THE SURFACE FROPA. HAVE KEPT LIKELY RAIN
CHANCES IN THE WESTERN HALF OF THE FORECAST AREA FOR TUESDAY...WITH
THE EASTERN HALF PROBABLY NEEDING A BUMP ONCE THE TIMING IS MORE
FIRM. HOWEVER...IT IS HARD TO JUSTIFY LIKELY POPS IN THE EAST AT
THIS TIME AS THE FROPA STILL APPEARS POSSIBLE IN MORE THAN ONE
FORECAST PERIOD.
ONCE THE FRONT CLEARS THE FORECAST AREA TO THE EAST...THERE SHOULD
BE A LULL IN THE PRECIPITATION THREAT. WHILE WRAP AROUND
PRECIPITATION IS POSSIBLE WEDNESDAY...THE BULK OF IT SHOULD HOLD OFF
UNTIL THE EXTENDED RANGE OF THE FORECAST PERIOD. THE SLOWER
PROGRESSION OF THE SYSTEM AND ASSOCIATED ARRIVAL OF COLDER AIR
SHOULD KEEP ANY PRECIPITATION FALLING AS RAIN THROUGH WEDNESDAY.
LONG TERM...WEDNESDAY NIGHT THROUGH SUNDAY...MODELS/ENSEMBLES
INITIALLY IN FAIRLY GOOD AGREEMENT WITH RESPECT TO FEATURES
EXPECTED TO IMPACT FORECAST AREA. HOWEVER...SPREAD INCREASES
SIGNIFICANTLY FROM FRIDAY TO THE END OF THE PERIOD.
UNFORTUNATELY...ONE ITEM THAT HAS DEVELOPED SINCE YESTERDAY IS
THAT IT LOOKS INCREASINGLY LIKELY THAT PRECIPITATION...MOSTLY
SNOW...IS POSSIBLE ON THANKSGIVING. THE SURFACE LOW THAT BROUGHT
THE RAINS ON TUESDAY WILL STILL BE OVER THE GREAT LAKES AT THE
START OF THE PERIOD. A STRONG UPPER WAVE WILL DIVE DOWN THE
BACKSIDE OF THIS VERTICALLY STACKED SYSTEM...LIKELY PRODUCING A
ROUND OF PRECIPITATION LATE WEDNESDAY NIGHT INTO THANKSGIVING DAY.
SOUNDING PROFILES/THICKNESS SCHEMES SUGGEST THAT ALL THE WARM AIR
WILL BE NEAR SURFACE BASED WHEN THIS PRECIPITATION WOULD FALL. SO
THE PRECIPITATION WILL BE FALLING AS SNOW...AND IT APPEARS THAT
THE ABOVE FREEZING NEAR SURFACE LAYER WILL BE TOO SHALLOW TO MELT
THE SNOW BEFORE IT REACHES THE GROUND. HOWEVER...AT THIS POINT...
LITTLE OR NO ACCUMULATION IS EXPECTED WITH THE SNOW. UPPER/SURFACE
RIDGING START TO BUILD IN FRIDAY INTO SATURDAY ENDING THE
PRECIPITATION AND ALLOWING TEMPERATURES TO MODERATE A BIT. THE
ARRIVAL OF THE NEXT WEATHER SYSTEM IS MUCH LESS CLEAR AT THIS
TIME. THE GFS SOLUTIONS TEND TO DEVELOP A MORE PHASED DEEP TROF
OVER EASTERN NORTH AMERICA...WHILE THE ECMWF SPLITS THE FLOW AND
CUTS OFF A LOW OVER THE SOUTHWEST UNITED STATES. THIS RESULTS IN
THE GFS BEING QUICKER AND STRONGER WITH THE NEXT SYSTEM BY LATE IN
THE WEEKEND. WILL CONTINUE TO SIDE WITH THE MORE CONSISTENT ECMWF
AND LEAVE THE END OF THE WEEKEND DRY AT THIS TIME.
BAK
&&
.AVIATION...
ISSUED 527 PM CST SUN NOV 22 2009
VFR CONDITIONS WILL CONTINUE TONIGHT BUT THEN LIGHT FOG WILL
DEVELOP AT ALL SITES AROUND 06Z LIKE IT DID LAST NIGHT. LIGHT FOG
WILL BURN OFF IN THE MORNING FOLLOWED BY A MID DECK ADVECTING INTO
THE AREA. PIA...BMI AND SPI COULD SEE SOME LOWER SC CLOUDS AT
3.5KFT WHILE DEC AND CMI WILL JUST SEE A MID DECK TOMORROW. LIGHT
EAST WINDS WILL BECOME SOUTHEAST TOMORROW AND CONTINUE INTO THE AFTERNOON.
AUTEN
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
000
FXUS63 KILX 222109 CCA
AFDILX
AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE LINCOLN IL
309 PM CST SUN NOV 22 2009
.DISCUSSION...
ISSUED 309 PM CST SUN NOV 22 2009
A PLEASANT FALL DAY IS UNFOLDING ACROSS CENTRAL AND SOUTHEAST
ILLINOIS...COURTESY OF A LARGE AREA OF HIGH PRESSURE CENTERED OVER
NEW ENGLAND. ONE MORE PRETTY NICE DAY IS ON TAP UNTIL SLOW MOVING
STORM SYSTEM ARRIVES FOR TUESDAY AND LINGERS IN THE AREA THROUGH
THANKSGIVING. THIS SLOW MOVING STORM SYSTEM...AND THE ASSOCIATED
PRECIPITATION THREAT AND IMPACT ON TEMPERATURES...IS OUR PRIMARY
FORECAST CONCERN TODAY.
12Z MODELS IN REASONABLE AGREEMENT THROUGH THE SHORT TERM.
HOWEVER...THEY ARE TRENDING SLOWER WITH OUR APPROACHING STORM
SYSTEM. HAVE TRENDED THE FORECAST TOWARD THE MIDDLE OF THE MODEL
ENVELOPE...WHICH IS QUICKER THAN THE NAM....BUT SLOWER THAN THE
GFS.
SHORT TERM...TONIGHT THROUGH WEDNESDAY...OUR STORM SYSTEM IS
ALREADY BEGINNING TO DEVELOP OVER THE CENTRAL PLAINS...AS
EVIDENCED BY THE LOW PRESSURE CENTER STARTING TO DEVELOP OVER
KANSAS. HOWEVER...IT WILL NOT REALLY DEEPEN OR START MOVING OUR
DIRECTION UNTIL IT INTERACTS WITH THE VIGOROUS UPPER WAVE
CURRENTLY DIVING THROUGH THE PACIFIC NORTHWEST. IN THE MEANTIME...
QUIET AND MILD LATE NOVEMBER CONDITIONS WILL PERSIST INTO MONDAY
NIGHT AS RETURN FLOW INCREASES ON THE BACK SIDE OF THE DEPARTING
AREA OF HIGH PRESSURE. THE DIURNAL TEMPERATURE RANGE MAY BE A BIT
SMALLER THROUGH MONDAY NIGHT THAN THE PAST FEW DAYS AS THE SYSTEM
BEGINS TO APPROACH AND CLOUD COVER INCREASES.
THE APPROACHING STORM AND TRAILING FRONTAL BOUNDARY IS STILL
EXPECTED TO MOVE THROUGH THE REGION ON TUESDAY...BUT THE FRONTAL
SPEED HAS SLIPPED BY ABOUT 6 HOURS. SO...AN 18Z TUE-06Z WED
PASSAGE LOOKS MORE LIKELY NOW THAN THE PREVIOUSLY EXPECTED 12Z
TUE-00Z WED PASSAGE. THE MAIN SURFACE LOW WILL LIFT INTO THE GREAT
LAKES TUESDAY NIGHT...WITH THE TRAILING COLD FRONT EXPECTED TO
CLEAR THE FORECAST AREA BY AROUND 06Z WEDNESDAY. THIS SYSTEM
SHOULD BE PRETTY DYNAMIC...THOUGH ALREADY OCCLUDED BY THE TIME IT
GETS HERE...WITH DECENT JET FORCING PROGGED OVER THE FORECAST AREA
ON TUESDAY COUPLED WITH THE SURFACE FROPA. HAVE KEPT LIKELY RAIN
CHANCES IN THE WESTERN HALF OF THE FORECAST AREA FOR TUESDAY...WITH
THE EASTERN HALF PROBABLY NEEDING A BUMP ONCE THE TIMING IS MORE
FIRM. HOWEVER...IT IS HARD TO JUSTIFY LIKELY POPS IN THE EAST AT
THIS TIME AS THE FROPA STILL APPEARS POSSIBLE IN MORE THAN ONE
FORECAST PERIOD.
ONCE THE FRONT CLEARS THE FORECAST AREA TO THE EAST...THERE SHOULD
BE A LULL IN THE PRECIPITATION THREAT. WHILE WRAP AROUND
PRECIPITATION IS POSSIBLE WEDNESDAY...THE BULK OF IT SHOULD HOLD OFF
UNTIL THE EXTENDED RANGE OF THE FORECAST PERIOD. THE SLOWER
PROGRESSION OF THE SYSTEM AND ASSOCIATED ARRIVAL OF COLDER AIR
SHOULD KEEP ANY PRECIPITATION FALLING AS RAIN THROUGH WEDNESDAY.
LONG TERM...WEDNESDAY NIGHT THROUGH SUNDAY...MODELS/ENSEMBLES
INITIALLY IN FAIRLY GOOD AGREEMENT WITH RESPECT TO FEATURES
EXPECTED TO IMPACT FORECAST AREA. HOWEVER...SPREAD INCREASES
SIGNIFICANTLY FROM FRIDAY TO THE END OF THE PERIOD.
UNFORTUNATELY...ONE ITEM THAT HAS DEVELOPED SINCE YESTERDAY IS
THAT IT LOOKS INCREASINGLY LIKELY THAT PRECIPITATION...MOSTLY
SNOW...IS POSSIBLE ON THANKSGIVING. THE SURFACE LOW THAT BROUGHT
THE RAINS ON TUESDAY WILL STILL BE OVER THE GREAT LAKES AT THE
START OF THE PERIOD. A STRONG UPPER WAVE WILL DIVE DOWN THE
BACKSIDE OF THIS VERTICALLY STACKED SYSTEM...LIKELY PRODUCING A
ROUND OF PRECIPITATION LATE WEDNESDAY NIGHT INTO THANKSGIVING DAY.
SOUNDING PROFILES/THICKNESS SCHEMES SUGGEST THAT ALL THE WARM AIR
WILL BE NEAR SURFACE BASED WHEN THIS PRECIPITATION WOULD FALL. SO
THE PRECIPITATION WILL BE FALLING AS SNOW...AND IT APPEARS THAT
THE ABOVE FREEZING NEAR SURFACE LAYER WILL BE TOO SHALLOW TO MELT
THE SNOW BEFORE IT REACHES THE GROUND. HOWEVER...AT THIS POINT...
LITTLE OR NO ACCUMULATION IS EXPECTED WITH THE SNOW. UPPER/SURFACE
RIDGING START TO BUILD IN FRIDAY INTO SATURDAY ENDING THE
PRECIPITATION AND ALLOWING TEMPERATURES TO MODERATE A BIT. THE
ARRIVAL OF THE NEXT WEATHER SYSTEM IS MUCH LESS CLEAR AT THIS
TIME. THE GFS SOLUTIONS TEND TO DEVELOP A MORE PHASED DEEP TROF
OVER EASTERN NORTH AMERICA...WHILE THE ECMWF SPLITS THE FLOW AND
CUTS OFF A LOW OVER THE SOUTHWEST UNITED STATES. THIS RESULTS IN
THE GFS BEING QUICKER AND STRONGER WITH THE NEXT SYSTEM BY LATE IN
THE WEEKEND. WILL CONTINUE TO SIDE WITH THE MORE CONSISTENT ECMWF
AND LEAVE THE END OF THE WEEKEND DRY AT THIS TIME.
BAK
&&
.AVIATION...
ISSUED 1132 AM CST SUN NOV 22 2009
HIGH PRESSURE ACROSS THE NE US...AND A SLOW MOVING COLD FRONT ACROSS
THE PLAINS...WILL KEEP THE WINDS IN A E TO SE DIRECTION OVER THE
NEXT 24 HOURS. AN UPPER LEVEL DISTURBANCE ACROSS SOUTHERN TN...WILL
KICK SOME CI INTO CENTRAL IL TODAY. AS THE COLD FRONT MOVES A BIT
CLOSER OVERNIGHT...THINK WINDS WILL BE A BIT STRONGER MON
MORNING...THAN THIS MORNING...AND VISIBILITIES WILL NOT DROP AS FAR.
HAVE MID CLOUDS MOVING INTO PIA...BMI AND SPI AFTER 14Z
MON...HOWEVER DO NOT THINK THE MID CLOUDS WL REACH DEC AND CMI
BEFORE 18Z.
DPK
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
000
FXUS63 KILX 222100
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
300 PM CST SUN NOV 22 2009
.DISCUSSION...
ISSUED 300 PM CST SUN NOV 22 2009
A PLEASANT FALL DAY IS UNFOLDING ACROSS CENTRAL AND SOUTHEAST
ILLINOIS...COURTESY OF A LARGE AREA OF HIGH PRESSURE CENTERED OVER
NEW ENGLAND. ONE MORE PRETTY NICE DAY IS ON TAP UNTIL SLOW MOVING
STORM SYSTEM ARRIVES FOR TUESDAY AND LINGERS IN THE AREA THROUGH
THANKSGIVING. THIS SLOW MOVING STORM SYSTEM...AND THE ASSOCIATED
PRECIPITATION THREAT AND IMPACT ON TEMPERATURES...IS OUR PRIMARY
FORECAST CONCERN TODAY.
12Z MODELS IN REASONABLE AGREEMENT THROUGH THE SHORT TERM.
HOWEVER...THEY ARE TRENDING SLOWER WITH OUR APPROACHING STORM
SYSTEM. HAVE TRENDED THE FORECAST TOWARD THE MIDDLE OF THE MODEL
ENVELOPE...WHICH US QUICKER THAN THE NAM....BUT SLOWER THAN THE
GFS.
SHORT TERM...TONIGHT THROUGH WEDNESDAY...OUR STORM SYSTEM IS
ALREADY BEGINNING TO DEVELOP OVER THE CENTRAL PLAINS...AS
EVIDENCED BY THE LOW PRESSURE CENTER STARTING TO DEVELOP OVER
KANSAS. HOWEVER...IT WILL NOT REALLY DEEPEN OR START MOVING OUR
DIRECTION UNTIL IT INTERACTS WITH THE VIGOROUS UPPER WAVE
CURRENTLY DIVING THROUGH THE PACIFIC NORTHWEST. IN THE MEANTIME...
QUIET AND MILD LATE NOVEMBER CONDITIONS WILL PERSIST INTO MONDAY
NIGHT AS RETURN FLOW INCREASES ON THE BACK SIDE OF THE DEPARTING
AREA OF HIGH PRESSURE. THE DIURNAL TEMPERATURE RANGE MAY BE A BIT
SMALLER THROUGH MONDAY NIGHT THAN THE PAST FEW DAYS AS THE SYSTEM
BEGINS TO APPROACH AND CLOUD COVER INCREASES.
THE APPROACHING STORM AND TRAILING FRONTAL BOUNDARY IS STILL
EXPECTED TO MOVE THROUGH THE REGION ON TUESDAY...BUT THE FRONTAL
SPEED HAS SLIPPED BY ABOUT 6 HOURS. SO...AN 18Z TUE-06Z WED
PASSAGE LOOKS MORE LIKELY NOW THAN THE PREVIOUSLY EXPECTED 12Z
TUE-00Z WED PASSAGE. THE MAIN SURFACE LOW WILL LIFT INTO THE GREAT
LAKES TUESDAY NIGHT...WITH THE TRAILING COLD FRONT EXPECTED TO
CLEAR THE FORECAST AREA BY AROUND 06Z WEDNESDAY. THIS SYSTEM
SHOULD BE PRETTY DYNAMIC...THOUGH ALREADY OCCLUDED BY THE TIME IT
GETS HERE...WITH DECENT JET FORCING PROGGED OVER THE FORECAST AREA
ON TUESDAY COUPLED WITH THE SURFACE FROPA. HAVE KEPT LIKELY RAIN
CHANCES IN THE WESTERN HALF OF THE FORECAST AREA FOR TUESDAY...WITH
THE EASTERN HALF PROBABLY NEEDING A BUMP AS WELL ONCE THE TIMING
IS MORE FIRM. HOWEVER...IT IS HARD TO JUSTIFY LIKELY POPS IN THE
EAST AT THIS TIME AS THE FROPA STILL APPEARS POSSIBLE IN MORE THAN
ONE FORECAST PERIOD.
ONCE THE FRONT CLEARS THE FORECAST AREA TO THE EAST...THERE SHOULD
BE A LULL IN THE PRECIPITATION THREAT. WHILE WRAP AROUND PRECIPITATION
IS POSSIBLE WEDNESDAY...THE BULK OF IT SHOULD HOLD OFF UNTIL THE
EXTENDED RANGE OF THE FORECAST PERIOD. THE SLOWER PROGRESSION OF
THE SYSTEM AND ASSOCIATED ARRIVAL OF COLDER AIR SHOULD KEEP ANY
PRECIPITATION FALLING AS RAIN THROUGH WEDNESDAY.
LONG TERM...WEDNESDAY NIGHT THROUGH SUNDAY...MODELS/ENSEMBLES
INITIALLY IN FAIRLY GOOD AGREEMENT WITH RESPECT TO FEATURES
EXPECTED TO IMPACT FORECAST AREA. HOWEVER...SPREAD INCREASES
SIGNIFICANTLY FROM FRIDAY TO THE END OF THE PERIOD.
UNFORTUNATELY...ONE ITEM THAT HAS DEVELOPED SINCE YESTERDAY IS
THAT IT LOOKS INCREASINGLY LIKELY THAT PRECIPITATION...MOSTLY
SNOW...IS POSSIBLE ON THANKSGIVING. THE SURFACE LOW THAT BROUGHT
THE RAINS ON TUESDAY WILL STILL BE OVER THE GREAT LAKES AT THE
START OF THE PERIOD. A STRONG UPPER WAVE WILL DIVE DOWN THE
BACKSIDE OF THIS VERTICALLY STACKED SYSTEM...LIKELY PRODUCING A
ROUND OF PRECIPITATION LATE WEDNESDAY NIGHT INTO THANKSGIVING DAY.
SOUNDING PROFILES/THICKNESS SCHEMES SUGGEST THAT ALL THE WARM AIR
WILL BE NEAR SURFACE BASED WHEN THIS PRECIPITATION WOULD FALL. SO
THE PRECIPITATION WILL BE FALLING AS SNOW...AND IT APPEARS THAT
THE ABOVE FREEZING NEAR SURFACE LAYER WILL BE TOO SHALLOW TO MELT
THE SNOW BEFORE IT REACHES THE GROUND. HOWEVER...AT THIS POINT...
LITTLE OR NO ACCUMULATION IS EXPECTED WITH THE SNOW. UPPER/SURFACE
RIDGING START TO BUILD IN FRIDAY INTO SATURDAY ENDING THE
PRECIPITATION AND ALLOWING TEMPERATURES TO MODERATE A BIT. THE
ARRIVAL OF THE NEXT WEATHER SYSTEM IS MUCH LESS CLEAR AT THIS
TIME. THE GFS SOLUTIONS TEND TO DEVELOP A MORE PHASED DEEP TROF
OVER EASTERN NORTH AMERICA...WHILE THE ECMWF SPLITS THE FLOW AND
CUTS OFF A LOW OVER THE SOUTHWEST UNITED STATES. THIS RESULTS IN
THE GFS BEING QUICKER AND STRONGER WITH THE NEXT SYSTEM BY LATE IN
THE WEEKEND. WILL CONTINUE TO SIDE WITH THE MORE CONSISTENT ECMWF
AND LEAVE THE END OF THE WEEKEND DRY AT THIS TIME.
BAK
&&
.AVIATION...
ISSUED 1132 AM CST SUN NOV 22 2009
HIGH PRESSURE ACROSS THE NE US...AND A SLOW MOVING COLD FRONT ACROSS THE
PLAINS...WILL KEEP THE WINDS IN A E TO SE DIRECTION OVER THE NEXT 24
HOURS. AN UPPER LEVEL DISTURBANCE ACROSS SOUTHERN TN...WILL KICK
SOME CI INTO CENTRAL IL TODAY. AS THE COLD FRONT MOVES A BIT CLOSER
OVERNIGHT...THINK WINDS WILL BE A BIT STRONGER MON MORNING...THAN
THIS MORNING...AND VISIBILITIES WILL NOT DROP AS FAR. HAVE MID
CLOUDS MOVING INTO PIA...BMI AND SPI AFTER 14Z MON...HOWEVER DO
NOT THINK THE MID CLOUDS WL REACH DEC AND CMI BEFORE 18Z.
DPK
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
000
FXUS63 KLOT 222043
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
243 PM CST SUN NOV 22 2009
.DISCUSSION...
243 PM CST
WITH CLOUD COVER PASSING TO THE WEST OF NORTHERN IL TONIGHT...PATCHY
FOG TO BE A CONCERN OVERNIGHT. VSBYS NOT DENSE THIS MRNG BUT LIKELY
TO BE SO OVERNIGHT IAW MOS OUTPUT. WILL AGAIN LEAVE EVENING OR MID
SHIFT WITH METWATCH RESPONSIBILITY ON WHETHER DENSE FOG ADVISORY IS
TO BE REQUIRED. WITH UPR RIDGE RETREATING TO THE NORTHEAST
TONIGHT...ILLINOIS LIKELY TO SEE WAA CI AND AC MOVING IN EARLY
MONDAY. CLOUDS SHUD INCREASE THRU THE DAY AND BECOME RATHER CLOUDY
OVERNIGHT MON NGT AS NEXT STORM SYSTEM DEEPENS OVER THE NRN ROCKIES
AND PLAINS. THIS SYSTEM CONTINUES TO DEEPEN AS IT MOVES ACROSS
THE PLAINS AND INTO THE MS VLY ON TUESDAY.
MODELS STILL TRENDING TOWARD OCCLUDING THIS SYSTEM FROM THE MID
AND UPR MS VLY TO THE GREAT LAKES TUES INTO TUES NGT. WHILE
CONCESSIONS AMONG MODELS HAVE BROUGHT THEM CLOSER ON STORM
TRACKING... TIMING IS STILL A BIT OFF. GFS IS MUCH QUICKER WHILE
ECMWF IS SLOWEST. NAM HOWEVER TAKES A MIDDLE GROUND AND WUD MAKE A
DECENT BLEND AMONG THEM. THIS COMPROMISE MAY BRING IN RAIN ON
TUESDAY BUT WUD LIKELY BACK OFF UNTIL THE AFTN. TENDENCY THEN MAY BE
TO PUSH BACK ONSET OF RAIN INTO THE EVENING. NEXT MODEL RUN OR TWO
SHUD PROBABLY RESOLVE THAT ISSUE.
ALL MODELS STILL RESOLVING TWO DISTINCT CLOSED UPR TROFS WITH THIS
HOLIDAY EVENT. THE FIRST TROF...OR UPR LOW...WILL SWING THRU
WEDNESDAY AND BRING COLDER AIR INTO THE MS VLY IN THE AFTN. WEAK UPR
RIDGING SEPARATES THIS FIRST TROF AND THE SECONDARY UPR TROF THAT
DROPS SE FROM MANITOBA TO NRN IL WED NGT. THE SECOND SHOT OF CAA
FOLLOWING THIS TROF IS MORE SIGNIFICANT. ANY RESIDUAL SHOWERS SHUD
START MIXING WITH SNOW WED EVENING AND CHANGING OVER TO ALL LIGHT
SNOW LATE WED NGT. POST LOW CYCLONIC FLOW IN THE COLD WRAPAROUND
WILL MAINTAIN A LGT SNOW OR FLURRY THREAT THRU THURSDAY BEFORE UPR
RIDGING WORKS IN FRIDAY AND ENDS ANYMORE PCPN.
UPPER RIDGING WORKING ACROSS THE MS VLY SAT SHUD RETURN SW FLOW TO
THE MIDWEST BY SUNDAY. LONG TERM PATTERNS ARE RATHER SUSPECT BUT
SUGGEST ANOTHER SYSTEM CENTERED OVER THE NRN PLAINS SWINGING ANOTHER
COLD FRONT ACROSS THE MS VLY LATE SAT INTO SUNDAY WITH RAIN CHANGING
TO SNOW SUNDAY AFTN. LOW CONFIDENCE BASED ON TIMING DISCONTINUITIES
SUGGESTS LEAVING OUT ANY MENTION OF IT FOR NOW.
RLB
&&
.AVIATION...
1130 AM CST
1800Z TAFS...LARGE HIGH PRESSURE OVR STLAWR VLY WILL MAINTAIN A
RIDGE SWWD TO MID MS VLY. THOUGH THIS RIDGE WILL GRADUALLY ERODE AS
SHORT WAVE NOW OVR CNTRL PLAINS APCHS AREA TONIGHT...LIGHT SELY SFC
FLOW WILL CONTINUE. SKIES ARE EXPECTED TO REMAIN GENLY CLR UNTIL
LATE TONIGHT WHEN SOME MID LVL CLOUDINESS ASSD WITH WAVE TO W BEGINS
TO OVERSPREAD PORTIONS OF NRN IL. OVERALL THOUGH...CONDITIONS
TONIGHT ARE NOT EXPECTED TO BE TOO DIFFERENT FROM WHAT THERY WERE
LAST NIGHT. AS A RESULT...MAIN WX PROBLEM NEXT 24 HRS WILL BE FOG
DEVELOPMENT AGAIN OVERNIGHT AND EARLY MON MORNING. POTL IS THERE
FOR SOME LIFR VIS...BUT EXPECT THESE CONDITIONS TO BE CONFINED TO
RURAL AREA OF NRN IL/NWRN INDIANA. CLOUDS TO INCR MONDAY MORNING AS
SYS TO W EJECTS NEWD THROUGH UPR MIDWEST AS DEEPER TROFFING DEVELOPS
OVR PLAINS STAS.
MERZLOCK
&&
.MARINE...
107 PM CST
A BROAD RIDGE OF HIGH PRESSURE EAST OF THE GREAT LAKES
WILL CONTINUE TO SLOWLY DRIFT EASTWARD. MEANWHILE...AN AREA OF LOW
PRESSURE WILL DEVELOP ACROSS THE SOUTHERN PLAINS TONIGHT...REACHING
WESTERN IOWA BY TUESDAY MORNING...AND NORTHERN ILLINOIS TUESDAY
NIGHT. THIS LOW WILL THEN MOVE ACROSS SOUTHERN LAKE MICHIGAN EARLY
WEDNESDAY MORNING.
THIS WILL PROMOTE A GENERALLY LIGHT SOUTHEAST WIND FLOW ACROSS
LAKE MICHIGAN THROUGH TUESDAY.
MERZLOCK
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&
$$
000
FXUS63 KLOT 221915
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
115 PM CST SUN NOV 22 2009
.DISCUSSION...
329 AM CST
SHORT TERM FOG CONCERNS AND EVOLUTION OF MID WEEK STORM SYSTEM
CONTINUE TO BE THE FOCI FOR THIS FORECAST PACKAGE.
THIS MORNING...SURFACE RIDGE THAT GAVE THE AREA A BEAUTIFUL SATURDAY
CONTINUES TO SHIFT OFF TO THE EAST. CALM WINDS AND GENERALLY CLEAR
SKIES ARE STILL IN PLACE OVER THE REGION...AND AREAS OF FOG HAVE
ONCE AGAIN FORMED THIS MORNING. DEWPOINT DEPRESSIONS ARE A FEW
DEGREES LARGER THIS MORNING AS OPPOSED TO LAST...AND AS A RESULT
VISIBILITIES HAVE GENERALLY STAYED IN THE 3-5 SM RANGE...AND REALLY
DON`T EXPECT VIS TO DROP TOO MUCH MORE THIS MORNING.
AFTER ANY RESIDUAL FOG BURNS OFF BY MID MORNING...TODAY LOOKS TO
BE A NEAR REPEAT OF SATURDAY...SAVE FOR PERHAPS A BIT MORE MID AND
HIGH LEVEL CLOUD COVER...ESPECIALLY ACROSS THE WESTERN
COUNTIES...AS WARM AIR ADVECTION CONTINUES TO ORGANIZE OFF TO THE
SOUTH AND WEST OF THE FORECAST AREA.
CLOUD COVER WILL STEADILY INCREASE TONIGHT AND MONDAY MORNING FROM
THE
WEST AS PREVIOUSLY ADVERTISED STORM SYSTEM TAKES SHAPE OVER
WESTERN HIGH PLAINS. NUMERICAL GUIDANCE HAS COME INTO
CONSIDERABLY BETTER AGREEMENT WITHIN THE LAST 24 HOURS REGARDING
THE EVOLUTION OF THIS SYSTEM. APPEARS THAT A LEAD SHORTWAVE WILL
BEGIN TO MOVE NORTHEAST TOWARD THE AREA DURING THE DAY MONDAY. AT
THIS TIME...LOOKS AS IF DRY EASTERLY FLOW WILL KEEP RAIN CHANCES
WITH THIS FIRST WAVE TO BELOW SLIGHT CHANCE MENTION.
ON TUESDAY...MAIN AREA OF RAIN IN ASSOCIATION WITH AN OCCLUDED
FRONT IS EXPECTED TO START MOVING ACROSS THE AREA FROM SOUTHWEST
TO NORTHEAST. RAIN SHOULD EXPAND ACROSS THE ENTIRE FORECAST AREA
BY TUESDAY NIGHT AND EARLY WEDNESDAY MORNING AS PARENT UPPER
TROUGH TRAVERSES THE AREA. THERMAL PROFILES TUESDAY AND DURING THE
EARLY MORNING WEDNESDAY APPEAR TO BE TOO WARM TO SUPPORT ANYTHING
OTHER THAN JUST RAIN. SECONDARY SHOT OF COLD AIR ASSOCIATED WITH
YET ANOTHER SHORTWAVE/UPPER LOW WILL BEGIN TO MOVE THROUGH THE
AREA WEDNESDAY AFTERNOON AND EVENING. AS COLDER AIR SPILLS SOUTH
ACROSS THE AREA...EXPECT PRECIPITATION TO CHANGE TO A RAIN/SNOW
MIX BEFORE TRANSITIONING TO ALL SNOW BY EARLY THURSDAY MORNING.
SCATTERED SNOW SHOWERS APPEAR TO BE POSSIBLE THROUGH THANKSGIVING
DAY AS UPPER LOW CONTINUES TO SPIN ACROSS UPPER GREAT LAKES. AT
THIS TIME...WHILE THERMAL PROFILE LOOKS TO BE COLD ENOUGH TO
SUPPORT SNOW...SURFACE TEMPERATURES ARE EXPECTED TO BE WARM ENOUGH
TO PRECLUDE ANYTHING IN THE WAY OF SIGNIFICANT ACCUMULATIONS.
LITTLE CHANGE MADE TO FORECAST FOR FRIDAY THROUGH SUNDAY. A FEW
SNOW SHOWERS LOOK TO REMAIN POSSIBLE ACROSS PORTIONS OF THE AREA
FRIDAY WITH THE AREA SITUATED UNDER COLD CYCLONIC FLOW ALOFT.
DEPENDING ON EXACT TRACK OF TROUGH AND SURFACE FEATURES...ALSO
COULDN`T
RULE OUT A FEW LIGHT LAKE EFFECT SNOW SHOWERS ACROSS PORTIONS OF
PORTER COUNTY INDIANA ON FRIDAY.
BOXELL
&&
.AVIATION...
1130 AM CST
1800Z TAFS...LARGE HIGH PRESSURE OVR STLAWR VLY WILL MAINTAIN A
RIDGE SWWD TO MID MS VLY. THOUGH THIS RIDGE WILL GRADUALLY ERODE AS
SHORT WAVE NOW OVR CNTRL PLAINS APCHS AREA TONIGHT...LIGHT SELY SFC
FLOW WILL CONTINUE. SKIES ARE EXPECTED TO REMAIN GENLY CLR UNTIL
LATE TONIGHT WHEN SOME MID LVL CLOUDINESS ASSD WITH WAVE TO W BEGINS
TO OVERSPREAD PORTIONS OF NRN IL. OVERALL THOUGH...CONDITIONS
TONIGHT ARE NOT EXPECTED TO BE TOO DIFFERENT FROM WHAT THERY WERE
LAST NIGHT. AS A RESULT...MAIN WX PROBLEM NEXT 24 HRS WILL BE FOG
DEVELOPMENT AGAIN OVERNIGHT AND EARLY MON MORNING. POTL IS THERE
FOR SOME LIFR VIS...BUT EXPECT THESE CONDITIONS TO BE CONFINED TO
RURAL AREA OF NRN IL/NWRN INDIANA. CLOUDS TO INCR MONDAY MORNING AS
SYS TO W EJECTS NEWD THROUGH UPR MIDWEST AS DEEPER TROFFING DEVELOPS
OVR PLAINS STAS.
MERZLOCK
&&
.MARINE...
107 PM CST
A BROAD RIDGE OF HIGH PRESSURE EAST OF THE GREAT LAKES
WILL CONTINUE TO SLOWLY DRIFT EASTWARD. MEANWHILE...AN AREA OF LOW
PRESSURE WILL DEVELOP ACROSS THE SOUTHERN PLAINS TONIGHT...REACHING
WESTERN IOWA BY TUESDAY MORNING...AND NORTHERN ILLINOIS TUESDAY
NIGHT. THIS LOW WILL THEN MOVE ACROSS SOUTHERN LAKE MICHIGAN EARLY
WEDNESDAY MORNING.
THIS WILL PROMOTE A GENERALLY LIGHT SOUTHEAST WIND FLOW ACROSS
LAKE MICHIGAN THROUGH TUESDAY.
MERZLOCK
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&
$$
000
FXUS63 KILX 221743
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1143 AM CST SUN NOV 22 2009
.DISCUSSION...
ISSUED 1025 AM CST SUN NOV 22 2009
HIGH PRESSURE TO THE EAST OF THE REGION AND A COLD FRONT TO THE WEST...WILL
KEEP A SOUTHEAST WIND FLOW ACROSS THE FORECAST AREA. CI FROM A
DISTURBANCE OVER SOUTHERN TN...ARE MOVING INTO THE SE PART OF THE
FORECAST AREA. INCREASED CLOUD COVER ACROSS THE SOUTHEAST. IN THE
NORTHWEST...CLOUD COVER IS GRADUALLY ERODING. TEMPERATURE AND WIND
TRENDS ARE ON TRACK. ADJUSTED SKY COVER SLIGHTLY TO ACCOUNT FOR
TRENDS ACROSS THE SOUTHEAST AND NORTHWEST. WILL SEND OUT AN UPDATE
SHORTLY TO INCREASE CLOUD COVER IN THE SE...NO MAJOR CHANGES THOUGH.
DPK
&&
.AVIATION...
ISSUED 1132 AM CST SUN NOV 22 2009
HIGH PRESSURE ACROSS THE NE US...AND A SLOW MOVING COLD FRONT ACROSS THE
PLAINS...WILL KEEP THE WINDS IN A E TO SE DIRECTION OVER THE NEXT 24
HOURS. AN UPPER LEVEL DISTURBANCE ACROSS SOUTHERN TN...WILL KICK
SOME CI INTO CENTRAL IL TODAY. AS THE COLD FRONT MOVES A BIT CLOSER
OVERNIGHT...THINK WINDS WILL BE A BIT STRONGER MON MORNING...THAN
THIS MORNING...AND VISIBILITIES WILL NOT DROP AS FAR. HAVE MID
CLOUDS MOVING INTO PIA...BMI AND SPI AFTER 14Z MON...HOWEVER DO
NOT THINK THE MID CLOUDS WL REACH DEC AND CMI BEFORE 18Z.
DPK
&&
.PREV DISCUSSION...
ISSUED 220 AM CST SUN NOV 22 2009
LATEST SURFACE MAP STILL SHOWING THE CWA UNDER THE INFLUENCE OF
HIGH PRESSURE RIDGING...EXTENDING FROM THE EASTERN GREAT LAKES
REGION. MID-LEVEL CLOUD DECK HAS BEEN TRYING TO ERODE ON ITS
EASTERN FLANK...BUT WAS INCREASING AGAIN IN WEST CENTRAL ILLINOIS
INTO MISSOURI. FOG ISSUES HAVE MAINLY BEEN LIMITED TO SELECT LOW
LYING AREAS NEAR THE INDIANA BORDER...BUT 3 TO 5 MILE VISIBILITIES
ARE NOT UNUSUAL EAST OF I-55. TEMPERATURES HAVE BEEN ABLE TO STAY
UP HIGHER THAN LAST NIGHT WITH A BIT OF A SOUTHEAST COMPONENT TO
THE WIND...BUT SOME 30S WERE FOUND IN A FEW AREAS EAST OF I-55.
MAIN ISSUE WITH THE FORECAST CONTINUES TO INVOLVE A STORM SYSTEM
MOVING THROUGH THE MID-MISSISSIPPI VALLEY TOWARD MIDWEEK. MODELS
ARE IN DECENT AGREEMENT WITH THE UPPER LEVEL FEATURES...AND ARE
COMING INTO BETTER ALIGNMENT WITH THE SPEED OF THE SURFACE FRONT
AND ASSOCIATED LOW.
SHORT TERM...TODAY THROUGH TUESDAY...
HIGH PRESSURE RIDGING EXPECTED TO REMAIN IN PLACE THROUGH
TODAY...THEN BEGIN TO BREAK DOWN THIS EVENING AS THE LOW/FRONT
ORGANIZES OVER THE PLAINS. ANOTHER MILD COUPLE OF DAYS EXPECTED AS
THE SOUTHEAST FLOW BECOMES MORE ENTRENCHED...WITH HIGHS CLOSE TO
60.
MAIN FEATURE OF INTEREST IS CURRENTLY JUST OFF THE OREGON COAST
PER LATEST WATER VAPOR IMAGERY. THIS WAVE SHOULD MOVE INTO THE
CENTRAL PLAINS BY LATE MONDAY EVENING AND DEEPEN INTO A CLOSED
LOW...WHICH WILL PUSH EAST INTO THE CWA BY EARLY WEDNESDAY
MORNING. ECMWF AND CANADIAN MODELS DEEPEN THE SURFACE LOW MUCH
MORE RAPIDLY AND STRONGER THAN THE NAM/GFS/SREF...BUT ARE SIMILAR
IN THE GENERAL TRACK INTO THE WISCONSIN/ILLINOIS BORDER REGION
THROUGH TUESDAY NIGHT AS THE LOW OCCLUDES. MAIN FRONTAL BOUNDARY
EXPECTED TO PASS THROUGH THE AREA TUESDAY EVENING. NET RESULT IS
TO LIMIT POPS TO THE WESTERN CWA MONDAY NIGHT AFTER MIDNIGHT...AND
CONTINUE WITH LIKELY POPS MUCH OF THE AREA LATER TUESDAY. HIGHEST
POPS TUESDAY NIGHT TO BE NEAR THE FRONT...BUT WILL BE PRESENT
EVERYWHERE DUE TO THREAT OF WRAPAROUND SHOWERS BEHIND THE LOW.
LONG TERM...WEDNESDAY THROUGH SATURDAY...
SECOND UPPER LOW EXPECTED TO PLUNGE SOUTHWARD INTO THE LOWER
MISSOURI VALLEY ON WEDNESDAY...PUSHING EAST ACROSS THE MIDWEST THE
REMAINDER OF THE WEEK. GFS/ECMWF BOTH SHOWING A SURFACE TROUGH/FRONT
SWINGING THROUGH THE MIDWEST ON THANKSGIVING DAY...FOLLOWED BY
HIGH PRESSURE BUILDING IN FROM THE WEST. MAIN CONCERN WILL BE WITH
POPS DURING WEDNESDAY AND THURSDAY. HAVE CONTINUED LOW CHANCE POPS
ACROSS THE NORTHERN CWA FOR WEDNESDAY...AND ADDED SLIGHT CHANCES
TO THIS AREA FOR THANKSGIVING DAY. BUFKIT SOUNDINGS INDICATE ANY
PRECIPITATION ON WEDNESDAY WOULD BE TRANSITIONING FROM RAIN TO
SNOW BY EVENING...AND THURSDAY PRECIPITATION WOULD MOST LIKELY BE
IN THE FORM OF SNOW.
GEELHART
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
000
FXUS63 KLOT 221740
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1130 AM CST SUN NOV 22 2009
.DISCUSSION...
329 AM CST
SHORT TERM FOG CONCERNS AND EVOLUTION OF MID WEEK STORM SYSTEM
CONTINUE TO BE THE FOCI FOR THIS FORECAST PACKAGE.
THIS MORNING...SURFACE RIDGE THAT GAVE THE AREA A BEAUTIFUL SATURDAY
CONTINUES TO SHIFT OFF TO THE EAST. CALM WINDS AND GENERALLY CLEAR
SKIES ARE STILL IN PLACE OVER THE REGION...AND AREAS OF FOG HAVE
ONCE AGAIN FORMED THIS MORNING. DEWPOINT DEPRESSIONS ARE A FEW
DEGREES LARGER THIS MORNING AS OPPOSED TO LAST...AND AS A RESULT
VISIBILITIES HAVE GENERALLY STAYED IN THE 3-5 SM RANGE...AND REALLY
DON`T EXPECT VIS TO DROP TOO MUCH MORE THIS MORNING.
AFTER ANY RESIDUAL FOG BURNS OFF BY MID MORNING...TODAY LOOKS TO
BE A NEAR REPEAT OF SATURDAY...SAVE FOR PERHAPS A BIT MORE MID AND
HIGH LEVEL CLOUD COVER...ESPECIALLY ACROSS THE WESTERN
COUNTIES...AS WARM AIR ADVECTION CONTINUES TO ORGANIZE OFF TO THE
SOUTH AND WEST OF THE FORECAST AREA.
CLOUD COVER WILL STEADILY INCREASE TONIGHT AND MONDAY MORNING FROM
THE
WEST AS PREVIOUSLY ADVERTISED STORM SYSTEM TAKES SHAPE OVER
WESTERN HIGH PLAINS. NUMERICAL GUIDANCE HAS COME INTO
CONSIDERABLY BETTER AGREEMENT WITHIN THE LAST 24 HOURS REGARDING
THE EVOLUTION OF THIS SYSTEM. APPEARS THAT A LEAD SHORTWAVE WILL
BEGIN TO MOVE NORTHEAST TOWARD THE AREA DURING THE DAY MONDAY. AT
THIS TIME...LOOKS AS IF DRY EASTERLY FLOW WILL KEEP RAIN CHANCES
WITH THIS FIRST WAVE TO BELOW SLIGHT CHANCE MENTION.
ON TUESDAY...MAIN AREA OF RAIN IN ASSOCIATION WITH AN OCCLUDED
FRONT IS EXPECTED TO START MOVING ACROSS THE AREA FROM SOUTHWEST
TO NORTHEAST. RAIN SHOULD EXPAND ACROSS THE ENTIRE FORECAST AREA
BY TUESDAY NIGHT AND EARLY WEDNESDAY MORNING AS PARENT UPPER
TROUGH TRAVERSES THE AREA. THERMAL PROFILES TUESDAY AND DURING THE
EARLY MORNING WEDNESDAY APPEAR TO BE TOO WARM TO SUPPORT ANYTHING
OTHER THAN JUST RAIN. SECONDARY SHOT OF COLD AIR ASSOCIATED WITH
YET ANOTHER SHORTWAVE/UPPER LOW WILL BEGIN TO MOVE THROUGH THE
AREA WEDNESDAY AFTERNOON AND EVENING. AS COLDER AIR SPILLS SOUTH
ACROSS THE AREA...EXPECT PRECIPITATION TO CHANGE TO A RAIN/SNOW
MIX BEFORE TRANSITIONING TO ALL SNOW BY EARLY THURSDAY MORNING.
SCATTERED SNOW SHOWERS APPEAR TO BE POSSIBLE THROUGH THANKSGIVING
DAY AS UPPER LOW CONTINUES TO SPIN ACROSS UPPER GREAT LAKES. AT
THIS TIME...WHILE THERMAL PROFILE LOOKS TO BE COLD ENOUGH TO
SUPPORT SNOW...SURFACE TEMPERATURES ARE EXPECTED TO BE WARM ENOUGH
TO PRECLUDE ANYTHING IN THE WAY OF SIGNIFICANT ACCUMULATIONS.
LITTLE CHANGE MADE TO FORECAST FOR FRIDAY THROUGH SUNDAY. A FEW
SNOW SHOWERS LOOK TO REMAIN POSSIBLE ACROSS PORTIONS OF THE AREA
FRIDAY WITH THE AREA SITUATED UNDER COLD CYCLONIC FLOW ALOFT.
DEPENDING ON EXACT TRACK OF TROUGH AND SURFACE FEATURES...ALSO
COULDN`T
RULE OUT A FEW LIGHT LAKE EFFECT SNOW SHOWERS ACROSS PORTIONS OF
PORTER COUNTY INDIANA ON FRIDAY.
BOXELL
&&
.AVIATION...
1130 AM CST
1800Z TAFS...LARGE HIGH PRESSURE OVR STLAWR VLY WILL MAINTAIN A
RIDGE SWWD TO MID MS VLY. THOUGH THIS RIDGE WILL GRADUALLY ERODE AS
SHORT WAVE NOW OVR CNTRL PLAINS APCHS AREA TONIGHT...LIGHT SELY SFC
FLOW WILL CONTINUE. SKIES ARE EXPECTED TO REMAIN GENLY CLR UNTIL
LATE TONIGHT WHEN SOME MID LVL CLOUDINESS ASSD WITH WAVE TO W BEGINS
TO OVERSPREAD PORTIONS OF NRN IL. OVERALL THOUGH...CONDITIONS
TONIGHT ARE NOT EXPECTED TO BE TOO DIFFERENT FROM WHAT THERY WERE
LAST NIGHT. AS A RESULT...MAIN WX PROBLEM NEXT 24 HRS WILL BE FOG
DEVELOPMENT AGAIN OVERNIGHT AND EARLY MON MORNING. POTL IS THERE
FOR SOME LIFR VIS...BUT EXPECT THESE CONDITIONS TO BE CONFINED TO
RURAL AREA OF NRN IL/NWRN INDIANA. CLOUDS TO INCR MONDAY MORNING AS
SYS TO W EJECTS NEWD THROUGH UPR MIDWEST AS DEEPER TROFFING DEVELOPS
OVR PLAINS STAS.
MERZLOCK
&&
.MARINE...
638 AM CST
CONTINUED EASTWARD PROGRESSION OF BROAD SURFACE ANTICYCLONE ACROSS
SOUTHEAST CANADA INTO NORTHEAST UNITED STATES WILL RESULT IN
SLIGHTLY STRENGTHENING SURFACE PRESSURE GRADIENT ACROSS WESTERN
GREAT LAKES REGION TODAY...MOST NOTABLY ACROSS NORTHERN HALF OF THE
LAKE WITH A WEAK SFC RIDGE AXIS EXPECTED TO LINGER ACROSS SOUTHERN
PORTIONS OF THE LAKE. EXPECTING LIGHT SOUTH WINDS TO GENERALLY
INCREASE INTO 10 TO 15 KT RANGE THIS MORNING...WITH SOME GUSTS TO
AROUND 20 KT THIS AFTERNOON ACROSS NORTHERN PART OF THE LAKE. ON
MONDAY...AN AREA OF SURFACE LOW PRESSURE WILL BEGIN TO TAKE SHAPE
ACROSS THE CENTRAL PLAINS AND WILL EVENTUALLY APPROACH SOUTHERN LAKE
MICHIGAN ON WEDNESDAY. THIS SYSTEM WILL BEGIN TO OCCLUDE
WEDNESDAY/THURSDAY WHICH WILL RESULT IN SFC LOW DEVELOPING FURTHER
BACK INTO COLD AIR WEST OF THE LAKE. AS UPPER LEVEL SYSTEM BEGINS TO
PULL OUT LATE THURSDAY...SFC LOW WILL TRACK INTO EASTERN GREAT
LAKES...WITH WINDS SHIFTING TO THE NORTHWEST AND MORE GUSTY IN
NATURE IN COLD ADVECTION AND STRONGER GRADIENT BEHIND THIS SYSTEM.
MARSILI
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&
$$
000
FXUS63 KILX 221642
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1042 AM CST SUN NOV 22 2009
.DISCUSSION...
ISSUED 1025 AM CST SUN NOV 22 2009
HIGH PRESSURE TO THE EAST OF THE REGION AND A COLD FRONT TO THE WEST...WILL
KEEP A SOUTHEAST WIND FLOW ACROSS THE FORECAST AREA. CI FROM A
DISTURBANCE OVER SOUTHERN TN...ARE MOVING INTO THE SE PART OF THE
FORECAST AREA. INCREASED CLOUD COVER ACROSS THE SOUTHEAST. IN THE
NORTHWEST...CLOUD COVER IS GRADUALLY ERODING. TEMPERATURE AND WIND
TRENDS ARE ON TRACK. ADJUSTED SKY COVER SLIGHTLY TO ACCOUNT FOR
TRENDS ACROSS THE SOUTHEAST AND NORTHWEST. WILL SEND OUT AN UPDATE
SHORTLY TO INCREASE CLOUD COVER IN THE SE...NO MAJOR CHANGES THOUGH.
DPK
&&
.AVIATION...
ISSUED 525 AM CST SUN NOV 22 2009
MAIN FORECAST CONCERN THIS PERIOD WILL BE WITH FOG AND ITS AFFECT
ON VSBYS FOR THE FIRST FEW HOURS OF THIS FCST PERIOD...OTHERWISE
VFR CONDITIONS WILL PREVAIL. BAND OF MID CLOUDS (6500-8500 FEET)
LOCATED OVR EXTREME WRN IL EXPECTED TO REMAIN JUST WEST OF PIA
AND SPI TODAY...WHILE THE RMDR OF THE SITES WL SEE ONLY A SCATTERING
OF HIGH CLOUDS DURING THE DAY. FORECAST SOUNDINGS SUGGEST THE MAIN
BAND OF MID LEVEL CLOUDS THAT HAVE BEEN STREAMING NWD OUT OF MO
ACRS WRN IL WILL CONTINUE THAT TREND INTO THIS EVENING...WHILE A
WEATHER DISTURBANCE ACRS THE GULF COAST STATES SPREADS SOME CIRRUS
NWD INTO CNTRL IL DURING THE DAY AND ESP TNT. SURFACE WINDS WL
REMAIN FROM AN EAST TO SOUTHEAST DIRECTION INTO TNT WITH SPEEDS
ARND 10 KTS TODAY AND FROM 5 TO 10 KTS TNT. WITH ABUNDANT LOW
LVL MOISTURE STILL IN PLACE ACRS THE REGION...AND DECOUPLING OF
THE WINDS TNT WL LEAD TO AREAS OF FOG. WL BRING IN 4-5 MILE VSBYS
ARND 06Z BUT COULD SEE THOSE DROP EVEN LOWER TWDS SUNRISE MONDAY.
SMITH
&&
.PREV DISCUSSION...
ISSUED 220 AM CST SUN NOV 22 2009
LATEST SURFACE MAP STILL SHOWING THE CWA UNDER THE INFLUENCE OF
HIGH PRESSURE RIDGING...EXTENDING FROM THE EASTERN GREAT LAKES
REGION. MID-LEVEL CLOUD DECK HAS BEEN TRYING TO ERODE ON ITS
EASTERN FLANK...BUT WAS INCREASING AGAIN IN WEST CENTRAL ILLINOIS
INTO MISSOURI. FOG ISSUES HAVE MAINLY BEEN LIMITED TO SELECT LOW
LYING AREAS NEAR THE INDIANA BORDER...BUT 3 TO 5 MILE VISIBILITIES
ARE NOT UNUSUAL EAST OF I-55. TEMPERATURES HAVE BEEN ABLE TO STAY
UP HIGHER THAN LAST NIGHT WITH A BIT OF A SOUTHEAST COMPONENT TO
THE WIND...BUT SOME 30S WERE FOUND IN A FEW AREAS EAST OF I-55.
MAIN ISSUE WITH THE FORECAST CONTINUES TO INVOLVE A STORM SYSTEM
MOVING THROUGH THE MID-MISSISSIPPI VALLEY TOWARD MIDWEEK. MODELS
ARE IN DECENT AGREEMENT WITH THE UPPER LEVEL FEATURES...AND ARE
COMING INTO BETTER ALIGNMENT WITH THE SPEED OF THE SURFACE FRONT
AND ASSOCIATED LOW.
SHORT TERM...TODAY THROUGH TUESDAY...
HIGH PRESSURE RIDGING EXPECTED TO REMAIN IN PLACE THROUGH
TODAY...THEN BEGIN TO BREAK DOWN THIS EVENING AS THE LOW/FRONT
ORGANIZES OVER THE PLAINS. ANOTHER MILD COUPLE OF DAYS EXPECTED AS
THE SOUTHEAST FLOW BECOMES MORE ENTRENCHED...WITH HIGHS CLOSE TO
60.
MAIN FEATURE OF INTEREST IS CURRENTLY JUST OFF THE OREGON COAST
PER LATEST WATER VAPOR IMAGERY. THIS WAVE SHOULD MOVE INTO THE
CENTRAL PLAINS BY LATE MONDAY EVENING AND DEEPEN INTO A CLOSED
LOW...WHICH WILL PUSH EAST INTO THE CWA BY EARLY WEDNESDAY
MORNING. ECMWF AND CANADIAN MODELS DEEPEN THE SURFACE LOW MUCH
MORE RAPIDLY AND STRONGER THAN THE NAM/GFS/SREF...BUT ARE SIMILAR
IN THE GENERAL TRACK INTO THE WISCONSIN/ILLINOIS BORDER REGION
THROUGH TUESDAY NIGHT AS THE LOW OCCLUDES. MAIN FRONTAL BOUNDARY
EXPECTED TO PASS THROUGH THE AREA TUESDAY EVENING. NET RESULT IS
TO LIMIT POPS TO THE WESTERN CWA MONDAY NIGHT AFTER MIDNIGHT...AND
CONTINUE WITH LIKELY POPS MUCH OF THE AREA LATER TUESDAY. HIGHEST
POPS TUESDAY NIGHT TO BE NEAR THE FRONT...BUT WILL BE PRESENT
EVERYWHERE DUE TO THREAT OF WRAPAROUND SHOWERS BEHIND THE LOW.
LONG TERM...WEDNESDAY THROUGH SATURDAY...
SECOND UPPER LOW EXPECTED TO PLUNGE SOUTHWARD INTO THE LOWER
MISSOURI VALLEY ON WEDNESDAY...PUSHING EAST ACROSS THE MIDWEST THE
REMAINDER OF THE WEEK. GFS/ECMWF BOTH SHOWING A SURFACE TROUGH/FRONT
SWINGING THROUGH THE MIDWEST ON THANKSGIVING DAY...FOLLOWED BY
HIGH PRESSURE BUILDING IN FROM THE WEST. MAIN CONCERN WILL BE WITH
POPS DURING WEDNESDAY AND THURSDAY. HAVE CONTINUED LOW CHANCE POPS
ACROSS THE NORTHERN CWA FOR WEDNESDAY...AND ADDED SLIGHT CHANCES
TO THIS AREA FOR THANKSGIVING DAY. BUFKIT SOUNDINGS INDICATE ANY
PRECIPITATION ON WEDNESDAY WOULD BE TRANSITIONING FROM RAIN TO
SNOW BY EVENING...AND THURSDAY PRECIPITATION WOULD MOST LIKELY BE
IN THE FORM OF SNOW.
GEELHART
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
000
FXUS63 KLOT 221240
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
640 AM CST SUN NOV 22 2009
.DISCUSSION...
329 AM CST
SHORT TERM FOG CONCERNS AND EVOLUTION OF MID WEEK STORM SYSTEM
CONTINUE TO BE THE FOCI FOR THIS FORECAST PACKAGE.
THIS MORNING...SURFACE RIDGE THAT GAVE THE AREA A BEAUTIFUL SATURDAY
CONTINUES TO SHIFT OFF TO THE EAST. CALM WINDS AND GENERALLY CLEAR
SKIES ARE STILL IN PLACE OVER THE REGION...AND AREAS OF FOG HAVE
ONCE AGAIN FORMED THIS MORNING. DEWPOINT DEPRESSIONS ARE A FEW
DEGREES LARGER THIS MORNING AS OPPOSED TO LAST...AND AS A RESULT
VISIBILITIES HAVE GENERALLY STAYED IN THE 3-5 SM RANGE...AND REALLY
DON`T EXPECT VIS TO DROP TOO MUCH MORE THIS MORNING.
AFTER ANY RESIDUAL FOG BURNS OFF BY MID MORNING...TODAY LOOKS TO
BE A NEAR REPEAT OF SATURDAY...SAVE FOR PERHAPS A BIT MORE MID AND
HIGH LEVEL CLOUD COVER...ESPECIALLY ACROSS THE WESTERN
COUNTIES...AS WARM AIR ADVECTION CONTINUES TO ORGANIZE OFF TO THE
SOUTH AND WEST OF THE FORECAST AREA.
CLOUD COVER WILL STEADILY INCREASE TONIGHT AND MONDAY MORNING FROM THE
WEST AS PREVIOUSLY ADVERTISED STORM SYSTEM TAKES SHAPE OVER
WESTERN HIGH PLAINS. NUMERICAL GUIDANCE HAS COME INTO
CONSIDERABLY BETTER AGREEMENT WITHIN THE LAST 24 HOURS REGARDING
THE EVOLUTION OF THIS SYSTEM. APPEARS THAT A LEAD SHORTWAVE WILL
BEGIN TO MOVE NORTHEAST TOWARD THE AREA DURING THE DAY MONDAY. AT
THIS TIME...LOOKS AS IF DRY EASTERLY FLOW WILL KEEP RAIN CHANCES
WITH THIS FIRST WAVE TO BELOW SLIGHT CHANCE MENTION.
ON TUESDAY...MAIN AREA OF RAIN IN ASSOCIATION WITH AN OCCLUDED
FRONT IS EXPECTED TO START MOVING ACROSS THE AREA FROM SOUTHWEST
TO NORTHEAST. RAIN SHOULD EXPAND ACROSS THE ENTIRE FORECAST AREA
BY TUESDAY NIGHT AND EARLY WEDNESDAY MORNING AS PARENT UPPER
TROUGH TRAVERSES THE AREA. THERMAL PROFILES TUESDAY AND DURING THE
EARLY MORNING WEDNESDAY APPEAR TO BE TOO WARM TO SUPPORT ANYTHING
OTHER THAN JUST RAIN. SECONDARY SHOT OF COLD AIR ASSOCIATED WITH
YET ANOTHER SHORTWAVE/UPPER LOW WILL BEGIN TO MOVE THROUGH THE
AREA WEDNESDAY AFTERNOON AND EVENING. AS COLDER AIR SPILLS SOUTH
ACROSS THE AREA...EXPECT PRECIPITATION TO CHANGE TO A RAIN/SNOW
MIX BEFORE TRANSITIONING TO ALL SNOW BY EARLY THURSDAY MORNING.
SCATTERED SNOW SHOWERS APPEAR TO BE POSSIBLE THROUGH THANKSGIVING
DAY AS UPPER LOW CONTINUES TO SPIN ACROSS UPPER GREAT LAKES. AT
THIS TIME...WHILE THERMAL PROFILE LOOKS TO BE COLD ENOUGH TO
SUPPORT SNOW...SURFACE TEMPERATURES ARE EXPECTED TO BE WARM ENOUGH
TO PRECLUDE ANYTHING IN THE WAY OF SIGNIFICANT ACCUMULATIONS.
LITTLE CHANGE MADE TO FORECAST FOR FRIDAY THROUGH SUNDAY. A FEW
SNOW SHOWERS LOOK TO REMAIN POSSIBLE ACROSS PORTIONS OF THE AREA
FRIDAY WITH THE AREA SITUATED UNDER COLD CYCLONIC FLOW ALOFT.
DEPENDING ON EXACT TRACK OF TROUGH AND SURFACE FEATURES...ALSO COULDN`T
RULE OUT A FEW LIGHT LAKE EFFECT SNOW SHOWERS ACROSS PORTIONS OF
PORTER COUNTY INDIANA ON FRIDAY.
BOXELL
&&
.AVIATION...
630 AM CST
1200 UTC TAFS...SURFACE HIGH EXTENDING FROM SOUTHEAST CANADA INTO
THE GREAT LAKES REGION WILL CONTINUE TO SLOWLY DRIFT SOUTHEAST
TODAY. UPPER LEVEL RIDGE WILL BE SLOW TO EXIT THE GREAT LAKES
REGION TODAY WHICH WILL ALLOW WEAK SFC RIDGE AXIS TO LINGER ACROSS
THE AREA. THUS...SFC PRESSURE GRADIENT WILL REMAIN FAIRLY WEAK
TODAY AND HAVE NOT MADE MANY CHANGES WITH SOUTHEAST WINDS THIS
MORNING OF 5 TO 10 KNOTS. WINDS SHOULD BACK MORE EAST SOUTHEAST
LATE THIS AFTERNOON AS THE SFC ANTICYCLONE EAST OF THE AREA SLOWLY
TRACKS NORTHEAST. CLOUD DECK ASSOCIATED WITH LOW LEVEL
WARM/MOISTURE ADVECTION WILL LIKELY REMAIN WEST OF NORTHEAST
ILLINOIS TERMINALS...AND ANY CIGS AT RFD THIS MORNING WILL REMAIN
VFR. PATCHY FOG AFFECTING TERMINALS AGAIN THIS MORNING AND LIKELY
VERY SHALLOW IN NATURE. DID INCLUDE TEMPO IFR VSBYS AT DPA THROUGH
14Z BUT AT RFD WILL KEEP VSBYS MVFR DUE TO INFLUENCE OF
AFOREMENTIONED CLOUDS AFFECTING NORTH CENTRAL ILLINOIS THIS
MORNING.
FOR TONIGHT...LIGHT EAST WINDS TO CONTINUE WITH JUST SOME
INCREASING HIGH CLOUDINESS AS UPPER LEVEL DISTURBANCE ACROSS THE
CENTRAL PLAINS APPROACHES. DEPENDING ON EXTENT OF HIGH
CLOUDINESS...MAY SEE A REPEAT OF SOME SHALLOW GROUND FOG AND HAVE
INCLUDED MVFR VSBYS FOR GYY/DPA/RFD AFTER 09Z.
MARSILI
&&
.MARINE...
638 AM CST
CONTINUED EASTWARD PROGRESSION OF BROAD SURFACE ANTICYCLONE ACROSS
SOUTHEAST CANADA INTO NORTHEAST UNITED STATES WILL RESULT IN
SLIGHTLY STRENGTHENING SURFACE PRESSURE GRADIENT ACROSS WESTERN
GREAT LAKES REGION TODAY...MOST NOTABLY ACROSS NORTHERN HALF OF THE
LAKE WITH A WEAK SFC RIDGE AXIS EXPECTED TO LINGER ACROSS SOUTHERN
PORTIONS OF THE LAKE. EXPECTING LIGHT SOUTH WINDS TO GENERALLY
INCREASE INTO 10 TO 15 KT RANGE THIS MORNING...WITH SOME GUSTS TO
AROUND 20 KT THIS AFTERNOON ACROSS NORTHERN PART OF THE LAKE. ON
MONDAY...AN AREA OF SURFACE LOW PRESSURE WILL BEGIN TO TAKE SHAPE
ACROSS THE CENTRAL PLAINS AND WILL EVENTUALLY APPROACH SOUTHERN LAKE
MICHIGAN ON WEDNESDAY. THIS SYSTEM WILL BEGIN TO OCCLUDE
WEDNESDAY/THURSDAY WHICH WILL RESULT IN SFC LOW DEVELOPING FURTHER
BACK INTO COLD AIR WEST OF THE LAKE. AS UPPER LEVEL SYSTEM BEGINS TO
PULL OUT LATE THURSDAY...SFC LOW WILL TRACK INTO EASTERN GREAT
LAKES...WITH WINDS SHIFTING TO THE NORTHWEST AND MORE GUSTY IN
NATURE IN COLD ADVECTION AND STRONGER GRADIENT BEHIND THIS SYSTEM.
MARSILI
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&
$$
000
FXUS63 KILX 221135
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
535 AM CST SUN NOV 22 2009
.DISCUSSION...
ISSUED 220 AM CST SUN NOV 22 2009
LATEST SURFACE MAP STILL SHOWING THE CWA UNDER THE INFLUENCE OF
HIGH PRESSURE RIDGING...EXTENDING FROM THE EASTERN GREAT LAKES
REGION. MID-LEVEL CLOUD DECK HAS BEEN TRYING TO ERODE ON ITS
EASTERN FLANK...BUT WAS INCREASING AGAIN IN WEST CENTRAL ILLINOIS
INTO MISSOURI. FOG ISSUES HAVE MAINLY BEEN LIMITED TO SELECT LOW
LYING AREAS NEAR THE INDIANA BORDER...BUT 3 TO 5 MILE VISIBILITIES
ARE NOT UNUSUAL EAST OF I-55. TEMPERATURES HAVE BEEN ABLE TO STAY
UP HIGHER THAN LAST NIGHT WITH A BIT OF A SOUTHEAST COMPONENT TO
THE WIND...BUT SOME 30S WERE FOUND IN A FEW AREAS EAST OF I-55.
MAIN ISSUE WITH THE FORECAST CONTINUES TO INVOLVE A STORM SYSTEM
MOVING THROUGH THE MID-MISSISSIPPI VALLEY TOWARD MIDWEEK. MODELS
ARE IN DECENT AGREEMENT WITH THE UPPER LEVEL FEATURES...AND ARE
COMING INTO BETTER ALIGNMENT WITH THE SPEED OF THE SURFACE FRONT
AND ASSOCIATED LOW.
SHORT TERM...TODAY THROUGH TUESDAY...
HIGH PRESSURE RIDGING EXPECTED TO REMAIN IN PLACE THROUGH
TODAY...THEN BEGIN TO BREAK DOWN THIS EVENING AS THE LOW/FRONT
ORGANIZES OVER THE PLAINS. ANOTHER MILD COUPLE OF DAYS EXPECTED AS
THE SOUTHEAST FLOW BECOMES MORE ENTRENCHED...WITH HIGHS CLOSE TO
60.
MAIN FEATURE OF INTEREST IS CURRENTLY JUST OFF THE OREGON COAST
PER LATEST WATER VAPOR IMAGERY. THIS WAVE SHOULD MOVE INTO THE
CENTRAL PLAINS BY LATE MONDAY EVENING AND DEEPEN INTO A CLOSED
LOW...WHICH WILL PUSH EAST INTO THE CWA BY EARLY WEDNESDAY
MORNING. ECMWF AND CANADIAN MODELS DEEPEN THE SURFACE LOW MUCH
MORE RAPIDLY AND STRONGER THAN THE NAM/GFS/SREF...BUT ARE SIMILAR
IN THE GENERAL TRACK INTO THE WISCONSIN/ILLINOIS BORDER REGION
THROUGH TUESDAY NIGHT AS THE LOW OCCLUDES. MAIN FRONTAL BOUNDARY
EXPECTED TO PASS THROUGH THE AREA TUESDAY EVENING. NET RESULT IS
TO LIMIT POPS TO THE WESTERN CWA MONDAY NIGHT AFTER MIDNIGHT...AND
CONTINUE WITH LIKELY POPS MUCH OF THE AREA LATER TUESDAY. HIGHEST
POPS TUESDAY NIGHT TO BE NEAR THE FRONT...BUT WILL BE PRESENT
EVERYWHERE DUE TO THREAT OF WRAPAROUND SHOWERS BEHIND THE LOW.
LONG TERM...WEDNESDAY THROUGH SATURDAY...
SECOND UPPER LOW EXPECTED TO PLUNGE SOUTHWARD INTO THE LOWER
MISSOURI VALLEY ON WEDNESDAY...PUSHING EAST ACROSS THE MIDWEST THE
REMAINDER OF THE WEEK. GFS/ECMWF BOTH SHOWING A SURFACE TROUGH/FRONT
SWINGING THROUGH THE MIDWEST ON THANKSGIVING DAY...FOLLOWED BY
HIGH PRESSURE BUILDING IN FROM THE WEST. MAIN CONCERN WILL BE WITH
POPS DURING WEDNESDAY AND THURSDAY. HAVE CONTINUED LOW CHANCE POPS
ACROSS THE NORTHERN CWA FOR WEDNESDAY...AND ADDED SLIGHT CHANCES
TO THIS AREA FOR THANKSGIVING DAY. BUFKIT SOUNDINGS INDICATE ANY
PRECIPITATION ON WEDNESDAY WOULD BE TRANSITIONING FROM RAIN TO
SNOW BY EVENING...AND THURSDAY PRECIPITATION WOULD MOST LIKELY BE
IN THE FORM OF SNOW.
GEELHART
&&
.AVIATION...
ISSUED 525 AM CST SUN NOV 22 2009
MAIN FORECAST CONCERN THIS PERIOD WILL BE WITH FOG AND ITS AFFECT
ON VSBYS FOR THE FIRST FEW HOURS OF THIS FCST PERIOD...OTHERWISE
VFR CONDITIONS WILL PREVAIL. BAND OF MID CLOUDS (6500-8500 FEET)
LOCATED OVR EXTREME WRN IL EXPECTED TO REMAIN JUST WEST OF PIA
AND SPI TODAY...WHILE THE RMDR OF THE SITES WL SEE ONLY A SCATTERING
OF HIGH CLOUDS DURING THE DAY. FORECAST SOUNDINGS SUGGEST THE MAIN
BAND OF MID LEVEL CLOUDS THAT HAVE BEEN STREAMING NWD OUT OF MO
ACRS WRN IL WILL CONTINUE THAT TREND INTO THIS EVENING...WHILE A
WEATHER DISTURBANCE ACRS THE GULF COAST STATES SPREADS SOME CIRRUS
NWD INTO CNTRL IL DURING THE DAY AND ESP TNT. SURFACE WINDS WL
REMAIN FROM AN EAST TO SOUTHEAST DIRECTION INTO TNT WITH SPEEDS
ARND 10 KTS TODAY AND FROM 5 TO 10 KTS TNT. WITH ABUNDANT LOW
LVL MOISTURE STILL IN PLACE ACRS THE REGION...AND DECOUPLING OF
THE WINDS TNT WL LEAD TO AREAS OF FOG. WL BRING IN 4-5 MILE VSBYS
ARND 06Z BUT COULD SEE THOSE DROP EVEN LOWER TWDS SUNRISE MONDAY.
SMITH
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
000
FXUS63 KLOT 220935
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
335 AM CST SUN NOV 22 2009
.DISCUSSION...
329 AM CST
SHORT TERM FOG CONCERNS AND EVOLUTION OF MID WEEK STORM SYSTEM
CONTINUE TO BE THE FOCI FOR THIS FORECAST PACKAGE.
THIS MORNING...SURFACE RIDGE THAT GAVE THE AREA A BEAUTIFUL SATURDAY
CONTINUES TO SHIFT OFF TO THE EAST. CALM WINDS AND GENERALLY CLEAR
SKIES ARE STILL IN PLACE OVER THE REGION...AND AREAS OF FOG HAVE
ONCE AGAIN FORMED THIS MORNING. DEWPOINT DEPRESSIONS ARE A FEW
DEGREES LARGER THIS MORNING AS OPPOSED TO LAST...AND AS A RESULT
VISIBILITIES HAVE GENERALLY STAYED IN THE 3-5 SM RANGE...AND REALLY
DON`T EXPECT VIS TO DROP TOO MUCH MORE THIS MORNING.
AFTER ANY RESIDUAL FOG BURNS OFF BY MID MORNING...TODAY LOOKS TO
BE A NEAR REPEAT OF SATURDAY...SAVE FOR PERHAPS A BIT MORE MID AND
HIGH LEVEL CLOUD COVER...ESPECIALLY ACROSS THE WESTERN
COUNTIES...AS WARM AIR ADVECTION CONTINUES TO ORGANIZE OFF TO THE
SOUTH AND WEST OF THE FORECAST AREA.
CLOUD COVER WILL STEADILY INCREASE TONIGHT AND MONDAY MORNING FROM THE
WEST AS PREVIOUSLY ADVERTISED STORM SYSTEM TAKES SHAPE OVER
WESTERN HIGH PLAINS. NUMERICAL GUIDANCE HAS COME INTO
CONSIDERABLY BETTER AGREEMENT WITHIN THE LAST 24 HOURS REGARDING
THE EVOLUTION OF THIS SYSTEM. APPEARS THAT A LEAD SHORTWAVE WILL
BEGIN TO MOVE NORTHEAST TOWARD THE AREA DURING THE DAY MONDAY. AT
THIS TIME...LOOKS AS IF DRY EASTERLY FLOW WILL KEEP RAIN CHANCES
WITH THIS FIRST WAVE TO BELOW SLIGHT CHANCE MENTION.
ON TUESDAY...MAIN AREA OF RAIN IN ASSOCIATION WITH AN OCCLUDED
FRONT IS EXPECTED TO START MOVING ACROSS THE AREA FROM SOUTHWEST
TO NORTHEAST. RAIN SHOULD EXPAND ACROSS THE ENTIRE FORECAST AREA
BY TUESDAY NIGHT AND EARLY WEDNESDAY MORNING AS PARENT UPPER
TROUGH TRAVERSES THE AREA. THERMAL PROFILES TUESDAY AND DURING THE
EARLY MORNING WEDNESDAY APPEAR TO BE TOO WARM TO SUPPORT ANYTHING
OTHER THAN JUST RAIN. SECONDARY SHOT OF COLD AIR ASSOCIATED WITH
YET ANOTHER SHORTWAVE/UPPER LOW WILL BEGIN TO MOVE THROUGH THE
AREA WEDNESDAY AFTERNOON AND EVENING. AS COLDER AIR SPILLS SOUTH
ACROSS THE AREA...EXPECT PRECIPITATION TO CHANGE TO A RAIN/SNOW
MIX BEFORE TRANSITIONING TO ALL SNOW BY EARLY THURSDAY MORNING.
SCATTERED SNOW SHOWERS APPEAR TO BE POSSIBLE THROUGH THANKSGIVING
DAY AS UPPER LOW CONTINUES TO SPIN ACROSS UPPER GREAT LAKES. AT
THIS TIME...WHILE THERMAL PROFILE LOOKS TO BE COLD ENOUGH TO
SUPPORT SNOW...SURFACE TEMPERATURES ARE EXPECTED TO BE WARM ENOUGH
TO PRECLUDE ANYTHING IN THE WAY OF SIGNIFICANT ACCUMULATIONS.
LITTLE CHANGE MADE TO FORECAST FOR FRIDAY THROUGH SUNDAY. A FEW
SNOW SHOWERS LOOK TO REMAIN POSSIBLE ACROSS PORTIONS OF THE AREA
FRIDAY WITH THE AREA SITUATED UNDER COLD CYCLONIC FLOW ALOFT.
DEPENDING ON EXACT TRACK OF TROUGH AND SURFACE FEATURES...ALSO COULDN`T
RULE OUT A FEW LIGHT LAKE EFFECT SNOW SHOWERS ACROSS PORTIONS OF
PORTER COUNTY INDIANA ON FRIDAY.
BOXELL
&&
.AVIATION...
0600 UTC TAFS...
THE WIND WILL BE SOUTHEAST AT 8 KNOTS OR LESS OVERNIGHT. A LARGE
HIGH OVER OHIO WILL SPREAD EAST INTO SOUTHERN QUEBEC THIS SUNDAY
MORNING. BY THIS EVENING THE HIGH CENTER WILL BE OVER NEW
BRUNSWICK AND THE HIGH WILL SPREAD WEST TO IOWA. THIS WILL GIVE A
SOUTHEAST WIND 5 TO 10 KNOTS SUNDAY. THE SATELLITE IMAGERY AND
SURFACE ANALYSIS SHOWS SOME CLOUDS AT 5000 TO 7000 FEET MOVING
INTO CENTRAL ILLINOIS. THESE CLOUDS MAY GIVE A CEILING OVER
ROCKFORD AND DUPAGE AIRPORTS THIS MORNING AND THE CLOUDS MAY MOVE
INTO CHICAGO. WILL FORECAST A BROKEN CEILING FOR THE AIRPORTS
AFTER 08 UTC. THE CLOUDS MAY DECREASE AS THEY MOVE EAST SO THEY
MAY BECOME SCATTERED. WE EXPECT MORE MOISTURE IN THE ATMOSPHERE
NEAR THE GROUND THIS MORNING. THE AIR ABOVE 1100 FEET WILL BE
RATHER DRY. WE WILL FORECAST FOG AND THE VISIBILITY WILL FALL TO
3 TO 4 MILES BY 09 UTC AT MOST OF THE AIRPORTS. THE FOG WILL BURN
OFF BY 15 UTC SUNDAY.
&&
.MARINE...
334 AM CST
CONTINUED EASTWARD PROGRESSION OF BROAD SURFACE ANTICYCLONE ACROSS
SOUTHEAST CANADA INTO NORTHEAST UNITED STATES WILL RESULT IN
SLIGHTLY STRENGTHENING SURFACE PRESSURE GRADIENT ACROSS WESTERN
GREAT LAKES REGION TODAY...MOST NOTABLY ACROSS NORTHERN HALF OF THE
LAKE WITH A WEAK SFC RIDGE AXIS EXPECTED TO LINGER ACROSS SOUTHERN
PORTIONS OF THE LAKE. EXPECTING LIGHT SOUTH WINDS TO GENERALLY
INCREASE INTO 10 TO 15 KT RANGE THIS MORNING...WITH SOME GUSTS TO
AROUND 20 KT THIS AFTERNOON ACROSS NORTHERN PART OF THE LAKE. ON
MONDAY...AN AREA OF SURFACE LOW PRESSURE WILL BEGIN TO TAKE SHAPE
ACROSS THE CENTRAL PLAINS AND WILL EVENTUALLY APPROACH SOUTHERN LAKE
MICHIGAN ON WEDNESDAY. THIS SYSTEM WILL BEGIN TO OCCLUDE
WEDNESDAY/THURSDAY WHICH WILL RESULT IN SFC LOW DEVELOPING FURTHER
BACK INTO COLD AIR WEST OF THE LAKE. AS UPPER LEVEL SYSTEM BEGINS TO
PULL OUT LATE THURSDAY...SFC LOW WILL TRACK INTO EASTERN GREAT
LAKES...WITH WINDS SHIFTING TO THE NORTHWEST AND MORE GUSTY IN
NATURE IN COLD ADVECTION AND STRONGER GRADIENT BEHIND THIS SYSTEM.
MARSILI
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&
$$
000
FXUS63 KLOT 220929
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
329 AM CST SUN NOV 22 2009
.DISCUSSION...
329 AM CST
SHORT TERM FOG CONCERNS AND EVOLUTION OF MID WEEK STORM SYSTEM
CONTINUE TO BE THE FOCI FOR THIS FORECAST PACKAGE.
THIS MORNING...SURFACE RIDGE THAT GAVE THE AREA A BEAUTIFUL SATURDAY
CONTINUES TO SHIFT OFF TO THE EAST. CALM WINDS AND GENERALLY CLEAR
SKIES ARE STILL IN PLACE OVER THE REGION...AND AREAS OF FOG HAVE
ONCE AGAIN FORMED THIS MORNING. DEWPOINT DEPRESSIONS ARE A FEW
DEGREES LARGER THIS MORNING AS OPPOSED TO LAST...AND AS A RESULT
VISIBILITIES HAVE GENERALLY STAYED IN THE 3-5 SM RANGE...AND REALLY
DON`T EXPECT VIS TO DROP TOO MUCH MORE THIS MORNING.
AFTER ANY RESIDUAL FOG BURNS OFF BY MID MORNING...TODAY LOOKS TO
BE A NEAR REPEAT OF SATURDAY...SAVE FOR PERHAPS A BIT MORE MID AND
HIGH LEVEL CLOUD COVER...ESPECIALLY ACROSS THE WESTERN
COUNTIES...AS WARM AIR ADVECTION CONTINUES TO ORGANIZE OFF TO THE
SOUTH AND WEST OF THE FORECAST AREA.
CLOUD COVER WILL STEADILY INCREASE TONIGHT AND MONDAY MORNING FROM THE
WEST AS PREVIOUSLY ADVERTISED STORM SYSTEM TAKES SHAPE OVER
WESTERN HIGH PLAINS. NUMERICAL GUIDANCE HAS COME INTO
CONSIDERABLY BETTER AGREEMENT WITHIN THE LAST 24 HOURS REGARDING
THE EVOLUTION OF THIS SYSTEM. APPEARS THAT A LEAD SHORTWAVE WILL
BEGIN TO MOVE NORTHEAST TOWARD THE AREA DURING THE DAY MONDAY. AT
THIS TIME...LOOKS AS IF DRY EASTERLY FLOW WILL KEEP RAIN CHANCES
WITH THIS FIRST WAVE TO BELOW SLIGHT CHANCE MENTION.
ON TUESDAY...MAIN AREA OF RAIN IN ASSOCIATION WITH AN OCCLUDED
FRONT IS EXPECTED TO START MOVING ACROSS THE AREA FROM SOUTHWEST
TO NORTHEAST. RAIN SHOULD EXPAND ACROSS THE ENTIRE FORECAST AREA
BY TUESDAY NIGHT AND EARLY WEDNESDAY MORNING AS PARENT UPPER
TROUGH TRAVERSES THE AREA. THERMAL PROFILES TUESDAY AND DURING THE
EARLY MORNING WEDNESDAY APPEAR TO BE TOO WARM TO SUPPORT ANYTHING
OTHER THAN JUST RAIN. SECONDARY SHOT OF COLD AIR ASSOCIATED WITH
YET ANOTHER SHORTWAVE/UPPER LOW WILL BEGIN TO MOVE THROUGH THE
AREA WEDNESDAY AFTERNOON AND EVENING. AS COLDER AIR SPILLS SOUTH
ACROSS THE AREA...EXPECT PRECIPITATION TO CHANGE TO A RAIN/SNOW
MIX BEFORE TRANSITIONING TO ALL SNOW BY EARLY THURSDAY MORNING.
SCATTERED SNOW SHOWERS APPEAR TO BE POSSIBLE THROUGH THANKSGIVING
DAY AS UPPER LOW CONTINUES TO SPIN ACROSS UPPER GREAT LAKES. AT
THIS TIME...WHILE THERMAL PROFILE LOOKS TO BE COLD ENOUGH TO
SUPPORT SNOW...SURFACE TEMPERATURES ARE EXPECTED TO BE WARM ENOUGH
TO PRECLUDE ANYTHING IN THE WAY OF SIGNIFICANT ACCUMULATIONS.
LITTLE CHANGE MADE TO FORECAST FOR FRIDAY THROUGH SUNDAY. A FEW
SNOW SHOWERS LOOK TO REMAIN POSSIBLE ACROSS PORTIONS OF THE AREA
FRIDAY WITH THE AREA SITUATED UNDER COLD CYCLONIC FLOW ALOFT.
DEPENDING ON EXACT TRACK OF TROUGH AND SURFACE FEATURES...ALSO COULDN`T
RULE OUT A FEW LIGHT LAKE EFFECT SNOW SHOWERS ACROSS PORTIONS OF
PORTER COUNTY INDIANA ON FRIDAY.
BOXELL
&&
.AVIATION...
0600 UTC TAFS...
THE WIND WILL BE SOUTHEAST AT 8 KNOTS OR LESS OVERNIGHT. A LARGE
HIGH OVER OHIO WILL SPREAD EAST INTO SOUTHERN QUEBEC THIS SUNDAY
MORNING. BY THIS EVENING THE HIGH CENTER WILL BE OVER NEW
BRUNSWICK AND THE HIGH WILL SPREAD WEST TO IOWA. THIS WILL GIVE A
SOUTHEAST WIND 5 TO 10 KNOTS SUNDAY. THE SATELLITE IMAGERY AND
SURFACE ANALYSIS SHOWS SOME CLOUDS AT 5000 TO 7000 FEET MOVING
INTO CENTRAL ILLINOIS. THESE CLOUDS MAY GIVE A CEILING OVER
ROCKFORD AND DUPAGE AIRPORTS THIS MORNING AND THE CLOUDS MAY MOVE
INTO CHICAGO. WILL FORECAST A BROKEN CEILING FOR THE AIRPORTS
AFTER 08 UTC. THE CLOUDS MAY DECREASE AS THEY MOVE EAST SO THEY
MAY BECOME SCATTERED. WE EXPECT MORE MOISTURE IN THE ATMOSPHERE
NEAR THE GROUND THIS MORNING. THE AIR ABOVE 1100 FEET WILL BE
RATHER DRY. WE WILL FORECAST FOG AND THE VISIBILITY WILL FALL TO
3 TO 4 MILES BY 09 UTC AT MOST OF THE AIRPORTS. THE FOG WILL BURN
OFF BY 15 UTC SUNDAY.
&&
.MARINE...
145 PM CST
NO SIGNIFICANT WINDS/WAVE EXPECTED THROUGH THE NEXT SEVERAL DAYS
WITH HIGH PRESSURE IN CONTROL OF THE WEATHER. LIGHT/VARIABLE
WINDS WILL TEND TO TURN MORE SOUTHERLY TONIGHT...ALBEIT NOT VERY
STRONGLY...AND GENERALLY CONTINUE IN A GENERAL SOUTHEASTERLY
DIRECTION THROUGH MIDWEEK.
IZZI
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&
$$
000
FXUS63 KILX 220821
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
221 AM CST SUN NOV 22 2009
.DISCUSSION...
ISSUED 220 AM CST SUN NOV 22 2009
LATEST SURFACE MAP STILL SHOWING THE CWA UNDER THE INFLUENCE OF
HIGH PRESSURE RIDGING...EXTENDING FROM THE EASTERN GREAT LAKES
REGION. MID-LEVEL CLOUD DECK HAS BEEN TRYING TO ERODE ON ITS
EASTERN FLANK...BUT WAS INCREASING AGAIN IN WEST CENTRAL ILLINOIS
INTO MISSOURI. FOG ISSUES HAVE MAINLY BEEN LIMITED TO SELECT LOW
LYING AREAS NEAR THE INDIANA BORDER...BUT 3 TO 5 MILE VISIBILITIES
ARE NOT UNUSUAL EAST OF I-55. TEMPERATURES HAVE BEEN ABLE TO STAY
UP HIGHER THAN LAST NIGHT WITH A BIT OF A SOUTHEAST COMPONENT TO
THE WIND...BUT SOME 30S WERE FOUND IN A FEW AREAS EAST OF I-55.
MAIN ISSUE WITH THE FORECAST CONTINUES TO INVOLVE A STORM SYSTEM
MOVING THROUGH THE MID-MISSISSIPPI VALLEY TOWARD MIDWEEK. MODELS
ARE IN DECENT AGREEMENT WITH THE UPPER LEVEL FEATURES...AND ARE
COMING INTO BETTER ALIGNMENT WITH THE SPEED OF THE SURFACE FRONT
AND ASSOCIATED LOW.
SHORT TERM...TODAY THROUGH TUESDAY...
HIGH PRESSURE RIDGING EXPECTED TO REMAIN IN PLACE THROUGH
TODAY...THEN BEGIN TO BREAK DOWN THIS EVENING AS THE LOW/FRONT
ORGANIZES OVER THE PLAINS. ANOTHER MILD COUPLE OF DAYS EXPECTED AS
THE SOUTHEAST FLOW BECOMES MORE ENTRENCHED...WITH HIGHS CLOSE TO
60.
MAIN FEATURE OF INTEREST IS CURRENTLY JUST OFF THE OREGON COAST
PER LATEST WATER VAPOR IMAGERY. THIS WAVE SHOULD MOVE INTO THE
CENTRAL PLAINS BY LATE MONDAY EVENING AND DEEPEN INTO A CLOSED
LOW...WHICH WILL PUSH EAST INTO THE CWA BY EARLY WEDNESDAY
MORNING. ECMWF AND CANADIAN MODELS DEEPEN THE SURFACE LOW MUCH
MORE RAPIDLY AND STRONGER THAN THE NAM/GFS/SREF...BUT ARE SIMILAR
IN THE GENERAL TRACK INTO THE WISCONSIN/ILLINOIS BORDER REGION
THROUGH TUESDAY NIGHT AS THE LOW OCCLUDES. MAIN FRONTAL BOUNDARY
EXPECTED TO PASS THROUGH THE AREA TUESDAY EVENING. NET RESULT IS
TO LIMIT POPS TO THE WESTERN CWA MONDAY NIGHT AFTER MIDNIGHT...AND
CONTINUE WITH LIKELY POPS MUCH OF THE AREA LATER TUESDAY. HIGHEST
POPS TUESDAY NIGHT TO BE NEAR THE FRONT...BUT WILL BE PRESENT
EVERYWHERE DUE TO THREAT OF WRAPAROUND SHOWERS BEHIND THE LOW.
LONG TERM...WEDNESDAY THROUGH SATURDAY...
SECOND UPPER LOW EXPECTED TO PLUNGE SOUTHWARD INTO THE LOWER
MISSOURI VALLEY ON WEDNESDAY...PUSHING EAST ACROSS THE MIDWEST THE
REMAINDER OF THE WEEK. GFS/ECMWF BOTH SHOWING A SURFACE TROUGH/FRONT
SWINGING THROUGH THE MIDWEST ON THANKSGIVING DAY...FOLLOWED BY
HIGH PRESSURE BUILDING IN FROM THE WEST. MAIN CONCERN WILL BE WITH
POPS DURING WEDNESDAY AND THURSDAY. HAVE CONTINUED LOW CHANCE POPS
ACROSS THE NORTHERN CWA FOR WEDNESDAY...AND ADDED SLIGHT CHANCES
TO THIS AREA FOR THANKSGIVING DAY. BUFKIT SOUNDINGS INDICATE ANY
PRECIPITATION ON WEDNESDAY WOULD BE TRANSITIONING FROM RAIN TO
SNOW BY EVENING...AND THURSDAY PRECIPITATION WOULD MOST LIKELY BE
IN THE FORM OF SNOW.
GEELHART
&&
.AVIATION...
ISSUED 1117 PM CST SAT NOV 21 2009
VFR CONDITIONS WILL PREVAIL MOST OF THE 24HR PERIOD OF ALL TAFS.
DEC AND CMI WILL HAVE MVFR VIS OVERNIGHT AND INTO THE MORNING
HOURS BUT DO NOT EXPECT THEM TO GO LOWER THAN THAT. MODEL RH
FIELDS INDICATE THAT BKN CLOUDS WILL REMAIN AT SPI AND PIA
OVERNIGHT BUT THEN BECOME SCATTERED BY MORNING AND THEN CLEAR BY
TOMORROW EVENING. DEC AND BMI WILL BE SCATTERED AND THEN BECOME
CLEAR IN THE MORNING. CMI WILL REMAIN CLEAR THROUGH THE PERIOD.
LIGHT SOUTHEAST WINDS WILL BECOME EASTERLY TOMORROW EVENING.
AUTEN
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
000
FXUS63 KILX 220517
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1117 PM CST SAT NOV 21 2009
.DISCUSSION...
ISSUED 856 PM CST SAT NOV 21 2009
CLOUD COVER OVER MOST OF THE CWA WHICH WILL KEEP TEMPS UP SO HAVE
ADJUSTED TEMPS BY 2-3 DEGREES IN THE WESTERN HALF OF THE CWA.
REMAINDER OF FORECAST LOOKS FINE. UPDATE COMING OUT SHORTLY.
AUTEN
&&
.AVIATION...
ISSUED 1117 PM CST SAT NOV 21 2009
VFR CONDITIONS WILL PREVAIL MOST OF THE 24HR PERIOD OF ALL TAFS.
DEC AND CMI WILL HAVE MVFR VIS OVERNIGHT AND INTO THE MORNING
HOURS BUT DO NOT EXPECT THEM TO GO LOWER THAN THAT. MODEL RH
FIELDS INDICATE THAT BKN CLOUDS WILL REMAIN AT SPI AND PIA
OVERNIGHT BUT THEN BECOME SCATTERED BY MORNING AND THEN CLEAR BY
TOMORROW EVENING. DEC AND BMI WILL BE SCATTERED AND THEN BECOME
CLEAR IN THE MORNING. CMI WILL REMAIN CLEAR THROUGH THE PERIOD.
LIGHT SOUTHEAST WINDS WILL BECOME EASTERLY TOMORROW EVENING.
AUTEN
&&
.PREV DISCUSSION...
ISSUED 305 PM CST SAT NOV 21 2009
A LARGE AREA OF HIGH PRESSURE CONTINUES TO DOMINATE THE EASTERN
1/3 OF NORTH AMERICA...INCLUDING CENTRAL AND SOUTHEAST ILLINOIS.
THIS WILL CONTINUE TO BE THE CASE INTO EARLY NEXT WEEK PROVIDING
QUIET AND MILD WEATHER FOR LATE NOVEMBER. MAIN ATTENTION THIS
FORECAST PACKAGE REVOLVES AROUND A STORM SYSTEM THAT IS EXPECTED TO
DEVELOP OVER THE PLAINS ON MONDAY. THIS SYSTEM WILL PUSH THROUGH THE
FORECAST AREA TUESDAY WITH AN ASSOCIATED RISK OF RAIN. MUCH COOLER
TEMPERATURES...AND POSSIBLY SOME WRAP AROUND LIGHT RAIN/SNOW...ARE
EXPECTED IN THE WAKE OF THE SYSTEM.
12Z FORECAST GUIDANCE IS STARTING TO COME TO A CONSENSUS ON THE
TIMING OF TUESDAY/S SYSTEM AFTER QUITE A BIT OF FLIP-FLOP AND
SPREAD OVER THE PAST SEVERAL RUNS. HOPEFULLY...THIS TREND
CONTINUES AND IS NOT A ONE MODEL RUN FLUKE. HAVE TRIED TO FOLLOW A
SOLUTION THAT IS IN THE MIDDLE OF THIS CLOSER MODEL SPREAD...WHICH
PROBABLY MOST CLOSELY RESEMBLES THE NAM OR SREF SOLUTION.
HOWEVER...NONE OF THE SOLUTIONS WOULD HAVE A TREMENDOUSLY DIFFERENT
OUTCOME AT THIS TIME.
SHORT TERM...TONIGHT THROUGH TUESDAY...QUIET AND MILD WEATHER IS
EXPECTED TO PERSIST THROUGH MONDAY AS THE SURFACE HIGH DRIFTS OFF
TO THE EAST AND RETURN FLOW INCREASES. ALOFT...A SPLIT FLOW...WITH
RELATIVELY WEAK FLOW OVERHEAD IS EXPECTED INTO MONDAY. DO NOT
EXPECT FOG TO BE MUCH OF A CONCERN THE NEXT TWO NIGHTS DESPITE
LIGHT WINDS AND PARTLY CLOUDY SKIES. THERE WAS NOT MUCH FOG THIS
MORNING...AND THE LOW LEVELS/SURFACE SOILS HAVE LIKELY DRIED A BIT
MORE WITH A FULL DAY OF INSOLATION.
A VIGOROUS UPPER WAVE IS EXPECTED TO DIG INTO THE CENTRAL PLAINS
ON MONDAY...WITH ASSOCIATED SURFACE CYCLOGENESIS. A LEAD SHORT
WAVE WILL EJECT ACROSS THE MIDWEST AS THE MAIN WAVE DIGS IN...BUT
MOISTURE PROFILES APPEAR TOO SHALLOW TO PRODUCE MUCH MORE THAN
CLOUDS WITH THE LEAD WAVE. THE MAIN SURFACE LOW WILL LIFT INTO THE
GREAT LAKES BY TUESDAY NIGHT...WITH THE TRAILING COLD FRONT
EXPECTED TO CLEAR THE FORECAST AREA BY AROUND 00Z WEDNESDAY. THIS
SYSTEM SHOULD BE PRETTY DYNAMIC...THOUGH ALREADY OCCLUDED BY THE
TIME IT GETS HERE...WITH DECENT JET FORCING PROGGED OVER THE
FORECAST AREA ON TUESDAY COUPLED WITH THE SURFACE FROPA. HAVE
BUMPED UP WESTERN HALF OF THE FORECAST AREA TO LIKELY RAIN CHANCES
FOR TUESDAY...WITH THE EASTERN HALF PROBABLY NEEDING A BUMP AS
WELL ONCE THE TIMING IS MORE FIRM.
LONG TERM...TUESDAY NIGHT THROUGH SATURDAY...A SECONDARY SHORT
WAVE IS PROGGED TO DIG INTO THE MEAN UPPER TROF CENTERED OVER THE
UPPER MIDWEST/GREAT LAKES ON WEDNESDAY. THIS WAVE MAY SPREAD SOME
WRAP AROUND PRECIPITATION INTO THE FORECAST AREA...THOUGH IT
SHOULD BE MORE WIDESPREAD FURTHER TO OUR NORTH. THE COLD AIR MASS
SURGING IN BEHIND THE SYSTEM MAY HAVE SOME SNOW MIXING IN WITH ANY
WRAP AROUND RAIN...ESPECIALLY TUESDAY NIGHT AND WEDNESDAY NIGHT
WHEN SURFACE TEMPERATURES ARE COOLEST. THE SYSTEM WILL FINALLY
PULL AWAY THANKSGIVING DAY INTO FRIDAY AS HIGH PRESSURE/UPPER
RIDGING BUILD IN...BRINGING A RETURN TO QUIETER AND MILDER WEATHER.
BAK
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
000
FXUS63 KLOT 220445
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1045 PM CST SAT NOV 21 2009
.DISCUSSION...
230 PM CST
NOT MUCH CHANGE IN CONCERNS FROM THIS MRNG. FOG POTENTIAL STILL
LOOMS TONIGHT DESPITE PASSING AC ADVECTION NWD THRU WRN IL. DEWPTS
STILL NR 40 TNGT AND WITH CALM WINDS AND NEARLY CLEAR SKIES...VSBYS
SHUD START LOWERING AFTER MDNGT AND PROGRESS TOWARD ZERO NR SUNRISE.
AC PASSAGE NWD THRU WESTERN IL WILL LIKELY KEEP VSBY UP ABV ADVISORY
CRITERIA FOR SECTIONS WEST OF I-39.
THIS PASSING AC TO CONTINUE THRU MONDAY AND PROMPT PARTLY CLOUDY
CONDITIONS UNTIL MONDAY NIGHT. WHILE MAX TEMPS TRY TO WARM UP EARLY
IN THE WEEK UNDER INCREASING SW FLOW ALOFT...INCREASED CLOUD COVER
AND LOWER SUN ANGLE WILL INHIBIT THE USUAL TEMP JUMPS ASSOCIATED
WITH EARLY AUTUMN WARM AIR ADVECTION...BUT RESPOND READILY TO ANY
UPCOMING COLD AIR ADVECTION. THUS HIGHS EARLY THIS WEEK WILL HOVER
IN THE 50S BUT SETTLE INTO THE 40S AFTER TUESDAY.
TUESDAY THEN IS THE FOCUS OF NEXT CONCERN. THE UPR LVL PATTERN
ASSOCIATED WITH THIS UPCOMING CHANGE HASNT EVEN MADE IT ONTO THE
WEST COAST AS YET...BUT SHUD BE MAKING LANDFALL LATE TONIGHT AND
CROSSING THE NRN ROCKIES SUNDAY NIGHT. DEEPENING MONDAY INTO A
STRONG CLOSED LOW IN THE PLAINS...EXPECT TO SEE AC AND CI ADVECTING
INTO THE MS VLY AND PCPN CHANCES INCREASE THU ILLINOIS LATE MON NGT
INTO TUESDAY.
ALL MODELS ARE TRENDING TOWARD OCCLUDING THIS SYSTEM FROM THE MID
AND UPR MS VLY TO THE GREAT LAKES BY MIDWEEK. TIMING AND STORM
CENTER LOCATION DIFFERENCES ARE STILL APPARENT AMONG THEM. THE ECMWF
IS CONSIDERABLY SLOWER THAN THE GFS AND NAM WITH THE NAM BEARING A
MORE SLY TRACK THAN EITHER OF THE TWO. AT THIS POINT...A BLEND IS
PROBABLY PRUDENT. THE GENERAL TREND THO IS FOR RAIN TO BEGIN TUESDAY
WITH COLD AIR WRAPAROUND FILTERING IN WEDNESDAY AND MIXING WITH
SNOW WED NIGHT BEFORE DIMINISHING TO SCATTERED FLURRIES THURSDAY.
GFS AND ECMWF ACTUALLY RESOLVE TWO DISTINCT CLOSED UPR TROFS
SWINGING THRU LATE IN THE WEEK. THE FIRST TROF ASSOCIATED WITH THE
RAIN ONSET ON TUESDAY SHUD SWING THRU ON WEDNESDAY. WEAK UPR
RIDGING MAY PUT AN END TO THE RAIN WED AFTN BEFORE A SECONDARY
CLIPPER-LIKE SYSTEM SWINGS DOWN FROM MANITOBA TO NRN IL WED NGT.
THE SECOND SHOT OF CAA FOLLOWING THIS SECOND TROF PASSAGE WILL BE
THE IMPULSE THAT PULLS DOWN AIR COLD ENUF TO CHANGEOVER TO A SNOW
MIXTURE. UPR RIDGING WORKING IN FRIDAY AND SATURDAY WILL END ANY
LINGERING FLURRIE CHANCES WHILE RETURNING WARM AIR ADVECTION FOR
THE WEEKEND.
RLB
&&
.AVIATION...
0600 UTC TAFS...
THE WIND WILL BE SOUTHEAST AT 8 KNOTS OR LESS OVERNIGHT. A LARGE
HIGH OVER OHIO WILL SPREAD EAST INTO SOUTHERN QUEBEC THIS SUNDAY
MORNING. BY THIS EVENING THE HIGH CENTER WILL BE OVER NEW
BRUNSWICK AND THE HIGH WILL SPREAD WEST TO IOWA. THIS WILL GIVE A
SOUTHEAST WIND 5 TO 10 KNOTS SUNDAY. THE SATELLITE IMAGERY AND
SURFACE ANALYSIS SHOWS SOME CLOUDS AT 5000 TO 7000 FEET MOVING
INTO CENTRAL ILLINOIS. THESE CLOUDS MAY GIVE A CEILING OVER
ROCKFORD AND DUPAGE AIRPORTS THIS MORNING AND THE CLOUDS MAY MOVE
INTO CHICAGO. WILL FORECAST A BROKEN CEILING FOR THE AIRPORTS
AFTER 08 UTC. THE CLOUDS MAY DECREASE AS THEY MOVE EAST SO THEY
MAY BECOME SCATTERED. WE EXPECT MORE MOISTURE IN THE ATMOSPHERE
NEAR THE GROUND THIS MORNING. THE AIR ABOVE 1100 FEET WILL BE
RATHER DRY. WE WILL FORECAST FOG AND THE VISIBILITY WILL FALL TO
3 TO 4 MILES BY 09 UTC AT MOST OF THE AIRPORTS. THE FOG WILL BURN
OFF BY 15 UTC SUNDAY.
&&
.MARINE...
145 PM CST
NO SIGNIFICANT WINDS/WAVE EXPECTED THROUGH THE NEXT SEVERAL DAYS
WITH HIGH PRESSURE IN CONTROL OF THE WEATHER. LIGHT/VARIABLE
WINDS WILL TEND TO TURN MORE SOUTHERLY TONIGHT...ALBEIT NOT VERY
STRONGLY...AND GENERALLY CONTINUE IN A GENERAL SOUTHEASTERLY
DIRECTION THROUGH MIDWEEK.
IZZI
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&
$$
000
FXUS63 KILX 220256
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
856 PM CST SAT NOV 21 2009
.DISCUSSION...
ISSUED 856 PM CST SAT NOV 21 2009
CLOUD COVER OVER MOST OF THE CWA WHICH WILL KEEP TEMPS UP SO HAVE
ADJUSTED TEMPS BY 2-3 DEGREES IN THE WESTERN HALF OF THE CWA.
REMAINDER OF FORECAST LOOKS FINE. UPDATE COMING OUT SHORTLY.
AUTEN
&&
.AVIATION...
ISSUED 514 PM CST SAT NOV 21 2009
VFR CONDITIONS SHOULD CONTINUE AT ALL SITES NEXT 24HRS. COULD SEE
SOME LIGHT FOG DURING THE MORNING HOURS AND HAVE INCLUDED A TEMPO
GROUP TO COVER AT ALL LOCATIONS. WINDS WILL BE EASTERLY OVERNIGHT
AND THEN BECOME MORE SOUTHEASTERLY IN THE MORNING AND THROUGHOUT
THE DAY.
AUTEN
&&
.PREV DISCUSSION...
ISSUED 305 PM CST SAT NOV 21 2009
A LARGE AREA OF HIGH PRESSURE CONTINUES TO DOMINATE THE EASTERN
1/3 OF NORTH AMERICA...INCLUDING CENTRAL AND SOUTHEAST ILLINOIS.
THIS WILL CONTINUE TO BE THE CASE INTO EARLY NEXT WEEK PROVIDING
QUIET AND MILD WEATHER FOR LATE NOVEMBER. MAIN ATTENTION THIS
FORECAST PACKAGE REVOLVES AROUND A STORM SYSTEM THAT IS EXPECTED TO
DEVELOP OVER THE PLAINS ON MONDAY. THIS SYSTEM WILL PUSH THROUGH THE
FORECAST AREA TUESDAY WITH AN ASSOCIATED RISK OF RAIN. MUCH COOLER
TEMPERATURES...AND POSSIBLY SOME WRAP AROUND LIGHT RAIN/SNOW...ARE
EXPECTED IN THE WAKE OF THE SYSTEM.
12Z FORECAST GUIDANCE IS STARTING TO COME TO A CONSENSUS ON THE
TIMING OF TUESDAY/S SYSTEM AFTER QUITE A BIT OF FLIP-FLOP AND
SPREAD OVER THE PAST SEVERAL RUNS. HOPEFULLY...THIS TREND
CONTINUES AND IS NOT A ONE MODEL RUN FLUKE. HAVE TRIED TO FOLLOW A
SOLUTION THAT IS IN THE MIDDLE OF THIS CLOSER MODEL SPREAD...WHICH
PROBABLY MOST CLOSELY RESEMBLES THE NAM OR SREF SOLUTION.
HOWEVER...NONE OF THE SOLUTIONS WOULD HAVE A TREMENDOUSLY DIFFERENT
OUTCOME AT THIS TIME.
SHORT TERM...TONIGHT THROUGH TUESDAY...QUIET AND MILD WEATHER IS
EXPECTED TO PERSIST THROUGH MONDAY AS THE SURFACE HIGH DRIFTS OFF
TO THE EAST AND RETURN FLOW INCREASES. ALOFT...A SPLIT FLOW...WITH
RELATIVELY WEAK FLOW OVERHEAD IS EXPECTED INTO MONDAY. DO NOT
EXPECT FOG TO BE MUCH OF A CONCERN THE NEXT TWO NIGHTS DESPITE
LIGHT WINDS AND PARTLY CLOUDY SKIES. THERE WAS NOT MUCH FOG THIS
MORNING...AND THE LOW LEVELS/SURFACE SOILS HAVE LIKELY DRIED A BIT
MORE WITH A FULL DAY OF INSOLATION.
A VIGOROUS UPPER WAVE IS EXPECTED TO DIG INTO THE CENTRAL PLAINS
ON MONDAY...WITH ASSOCIATED SURFACE CYCLOGENESIS. A LEAD SHORT
WAVE WILL EJECT ACROSS THE MIDWEST AS THE MAIN WAVE DIGS IN...BUT
MOISTURE PROFILES APPEAR TOO SHALLOW TO PRODUCE MUCH MORE THAN
CLOUDS WITH THE LEAD WAVE. THE MAIN SURFACE LOW WILL LIFT INTO THE
GREAT LAKES BY TUESDAY NIGHT...WITH THE TRAILING COLD FRONT
EXPECTED TO CLEAR THE FORECAST AREA BY AROUND 00Z WEDNESDAY. THIS
SYSTEM SHOULD BE PRETTY DYNAMIC...THOUGH ALREADY OCCLUDED BY THE
TIME IT GETS HERE...WITH DECENT JET FORCING PROGGED OVER THE
FORECAST AREA ON TUESDAY COUPLED WITH THE SURFACE FROPA. HAVE
BUMPED UP WESTERN HALF OF THE FORECAST AREA TO LIKELY RAIN CHANCES
FOR TUESDAY...WITH THE EASTERN HALF PROBABLY NEEDING A BUMP AS
WELL ONCE THE TIMING IS MORE FIRM.
LONG TERM...TUESDAY NIGHT THROUGH SATURDAY...A SECONDARY SHORT
WAVE IS PROGGED TO DIG INTO THE MEAN UPPER TROF CENTERED OVER THE
UPPER MIDWEST/GREAT LAKES ON WEDNESDAY. THIS WAVE MAY SPREAD SOME
WRAP AROUND PRECIPITATION INTO THE FORECAST AREA...THOUGH IT
SHOULD BE MORE WIDESPREAD FURTHER TO OUR NORTH. THE COLD AIR MASS
SURGING IN BEHIND THE SYSTEM MAY HAVE SOME SNOW MIXING IN WITH ANY
WRAP AROUND RAIN...ESPECIALLY TUESDAY NIGHT AND WEDNESDAY NIGHT
WHEN SURFACE TEMPERATURES ARE COOLEST. THE SYSTEM WILL FINALLY
PULL AWAY THANKSGIVING DAY INTO FRIDAY AS HIGH PRESSURE/UPPER
RIDGING BUILD IN...BRINGING A RETURN TO QUIETER AND MILDER WEATHER.
BAK
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
000
FXUS63 KLOT 220012
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
612 PM CST SAT NOV 21 2009
.DISCUSSION...
230 PM CST
NOT MUCH CHANGE IN CONCERNS FROM THIS MRNG. FOG POTENTIAL STILL
LOOMS TONIGHT DESPITE PASSING AC ADVECTION NWD THRU WRN IL. DEWPTS
STILL NR 40 TNGT AND WITH CALM WINDS AND NEARLY CLEAR SKIES...VSBYS
SHUD START LOWERING AFTER MDNGT AND PROGRESS TOWARD ZERO NR SUNRISE.
AC PASSAGE NWD THRU WESTERN IL WILL LIKELY KEEP VSBY UP ABV ADVISORY
CRITERIA FOR SECTIONS WEST OF I-39.
THIS PASSING AC TO CONTINUE THRU MONDAY AND PROMPT PARTLY CLOUDY
CONDITIONS UNTIL MONDAY NIGHT. WHILE MAX TEMPS TRY TO WARM UP EARLY
IN THE WEEK UNDER INCREASING SW FLOW ALOFT...INCREASED CLOUD COVER
AND LOWER SUN ANGLE WILL INHIBIT THE USUAL TEMP JUMPS ASSOCIATED
WITH EARLY AUTUMN WARM AIR ADVECTION...BUT RESPOND READILY TO ANY
UPCOMING COLD AIR ADVECTION. THUS HIGHS EARLY THIS WEEK WILL HOVER
IN THE 50S BUT SETTLE INTO THE 40S AFTER TUESDAY.
TUESDAY THEN IS THE FOCUS OF NEXT CONCERN. THE UPR LVL PATTERN
ASSOCIATED WITH THIS UPCOMING CHANGE HASNT EVEN MADE IT ONTO THE
WEST COAST AS YET...BUT SHUD BE MAKING LANDFALL LATE TONIGHT AND
CROSSING THE NRN ROCKIES SUNDAY NIGHT. DEEPENING MONDAY INTO A
STRONG CLOSED LOW IN THE PLAINS...EXPECT TO SEE AC AND CI ADVECTING
INTO THE MS VLY AND PCPN CHANCES INCREASE THU ILLINOIS LATE MON NGT
INTO TUESDAY.
ALL MODELS ARE TRENDING TOWARD OCCLUDING THIS SYSTEM FROM THE MID
AND UPR MS VLY TO THE GREAT LAKES BY MIDWEEK. TIMING AND STORM
CENTER LOCATION DIFFERENCES ARE STILL APPARENT AMONG THEM. THE ECMWF
IS CONSIDERABLY SLOWER THAN THE GFS AND NAM WITH THE NAM BEARING A
MORE SLY TRACK THAN EITHER OF THE TWO. AT THIS POINT...A BLEND IS
PROBABLY PRUDENT. THE GENERAL TREND THO IS FOR RAIN TO BEGIN TUESDAY
WITH COLD AIR WRAPAROUND FILTERING IN WEDNESDAY AND MIXING WITH
SNOW WED NIGHT BEFORE DIMINISHING TO SCATTERED FLURRIES THURSDAY.
GFS AND ECMWF ACTUALLY RESOLVE TWO DISTINCT CLOSED UPR TROFS
SWINGING THRU LATE IN THE WEEK. THE FIRST TROF ASSOCIATED WITH THE
RAIN ONSET ON TUESDAY SHUD SWING THRU ON WEDNESDAY. WEAK UPR
RIDGING MAY PUT AN END TO THE RAIN WED AFTN BEFORE A SECONDARY
CLIPPER-LIKE SYSTEM SWINGS DOWN FROM MANITOBA TO NRN IL WED NGT.
THE SECOND SHOT OF CAA FOLLOWING THIS SECOND TROF PASSAGE WILL BE
THE IMPULSE THAT PULLS DOWN AIR COLD ENUF TO CHANGEOVER TO A SNOW
MIXTURE. UPR RIDGING WORKING IN FRIDAY AND SATURDAY WILL END ANY
LINGERING FLURRIE CHANCES WHILE RETURNING WARM AIR ADVECTION FOR
THE WEEKEND.
RLB
&&
.AVIATION...
0000 UTC TAFS...THE WIND WILL BE NEAR CALM TONIGHT. A LARGE HIGH
OVER OHIO WILL SPREAD EAST INTO SOUTHERN QUEBEC BY SUNDAY MORNING.
BY SUNDAY EVENING THE HIGH CENTER WILL BE OVER NEW BRUNSWICK AND
THE HIGH WILL SPREAD WEST TO IOWA. THIS WILL GIVE A SOUTHEAST WIND
5 TO 10 KNOTS. WE EXPECT MORE MOISTURE IN THE ATMOSPHERE NEAR THE
GROUND OVERNIGHT. THE AIR ABOVE 3000 FEET WILL BE RATHER DRY BY
SUNDAY MORNING. WE WILL FORECAST FOG AND THE VISIBILITY WILL FALL
TO 3 TO 4 MILES BY 04 UTC AT MOST OF THE AIRPORTS. BECAUSE OF THE
SURROUNDING LAND USE...WE WOULD EXPECT MORE FOG AND THE
VISIBILITY AS LOW AS 1 TO 3 MILES AT ROCKFORD AND DUPAGE. THOSE
AIRPORTS ARE IN MORE RURAL LOCATIONS. THE FOG WILL BURN OFF BY 16
UTC SUNDAY. WE EXPECT CLOUDS AT 25000 FEET AS AN UPPER AIR TROUGH
MOVES INTO UPPER MISSISSIPPI VALLEY.
&&
.MARINE...
145 PM CST
NO SIGNIFICANT WINDS/WAVE EXPECTED THROUGH THE NEXT SEVERAL DAYS
WITH HIGH PRESSURE IN CONTROL OF THE WEATHER. LIGHT/VARIABLE
WINDS WILL TEND TO TURN MORE SOUTHERLY TONIGHT...ALBEIT NOT VERY
STRONGLY...AND GENERALLY CONTINUE IN A GENERAL SOUTHEASTERLY
DIRECTION THROUGH MIDWEEK.
IZZI
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&
$$
000
FXUS63 KILX 212314
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
514 PM CST SAT NOV 21 2009
.DISCUSSION...
ISSUED 305 PM CST SAT NOV 21 2009
A LARGE AREA OF HIGH PRESSURE CONTINUES TO DOMINATE THE EASTERN
1/3 OF NORTH AMERICA...INCLUDING CENTRAL AND SOUTHEAST ILLINOIS.
THIS WILL CONTINUE TO BE THE CASE INTO EARLY NEXT WEEK PROVIDING
QUIET AND MILD WEATHER FOR LATE NOVEMBER. MAIN ATTENTION THIS
FORECAST PACKAGE REVOLVES AROUND A STORM SYSTEM THAT IS EXPECTED TO
DEVELOP OVER THE PLAINS ON MONDAY. THIS SYSTEM WILL PUSH THROUGH THE
FORECAST AREA TUESDAY WITH AN ASSOCIATED RISK OF RAIN. MUCH COOLER
TEMPERATURES...AND POSSIBLY SOME WRAP AROUND LIGHT RAIN/SNOW...ARE
EXPECTED IN THE WAKE OF THE SYSTEM.
12Z FORECAST GUIDANCE IS STARTING TO COME TO A CONSENSUS ON THE
TIMING OF TUESDAY/S SYSTEM AFTER QUITE A BIT OF FLIP-FLOP AND
SPREAD OVER THE PAST SEVERAL RUNS. HOPEFULLY...THIS TREND
CONTINUES AND IS NOT A ONE MODEL RUN FLUKE. HAVE TRIED TO FOLLOW A
SOLUTION THAT IS IN THE MIDDLE OF THIS CLOSER MODEL SPREAD...WHICH
PROBABLY MOST CLOSELY RESEMBLES THE NAM OR SREF SOLUTION.
HOWEVER...NONE OF THE SOLUTIONS WOULD HAVE A TREMENDOUSLY DIFFERENT
OUTCOME AT THIS TIME.
SHORT TERM...TONIGHT THROUGH TUESDAY...QUIET AND MILD WEATHER IS
EXPECTED TO PERSIST THROUGH MONDAY AS THE SURFACE HIGH DRIFTS OFF
TO THE EAST AND RETURN FLOW INCREASES. ALOFT...A SPLIT FLOW...WITH
RELATIVELY WEAK FLOW OVERHEAD IS EXPECTED INTO MONDAY. DO NOT
EXPECT FOG TO BE MUCH OF A CONCERN THE NEXT TWO NIGHTS DESPITE
LIGHT WINDS AND PARTLY CLOUDY SKIES. THERE WAS NOT MUCH FOG THIS
MORNING...AND THE LOW LEVELS/SURFACE SOILS HAVE LIKELY DRIED A BIT
MORE WITH A FULL DAY OF INSOLATION.
A VIGOROUS UPPER WAVE IS EXPECTED TO DIG INTO THE CENTRAL PLAINS
ON MONDAY...WITH ASSOCIATED SURFACE CYCLOGENESIS. A LEAD SHORT
WAVE WILL EJECT ACROSS THE MIDWEST AS THE MAIN WAVE DIGS IN...BUT
MOISTURE PROFILES APPEAR TOO SHALLOW TO PRODUCE MUCH MORE THAN
CLOUDS WITH THE LEAD WAVE. THE MAIN SURFACE LOW WILL LIFT INTO THE
GREAT LAKES BY TUESDAY NIGHT...WITH THE TRAILING COLD FRONT
EXPECTED TO CLEAR THE FORECAST AREA BY AROUND 00Z WEDNESDAY. THIS
SYSTEM SHOULD BE PRETTY DYNAMIC...THOUGH ALREADY OCCLUDED BY THE
TIME IT GETS HERE...WITH DECENT JET FORCING PROGGED OVER THE
FORECAST AREA ON TUESDAY COUPLED WITH THE SURFACE FROPA. HAVE
BUMPED UP WESTERN HALF OF THE FORECAST AREA TO LIKELY RAIN CHANCES
FOR TUESDAY...WITH THE EASTERN HALF PROBABLY NEEDING A BUMP AS
WELL ONCE THE TIMING IS MORE FIRM.
LONG TERM...TUESDAY NIGHT THROUGH SATURDAY...A SECONDARY SHORT
WAVE IS PROGGED TO DIG INTO THE MEAN UPPER TROF CENTERED OVER THE
UPPER MIDWEST/GREAT LAKES ON WEDNESDAY. THIS WAVE MAY SPREAD SOME
WRAP AROUND PRECIPITATION INTO THE FORECAST AREA...THOUGH IT
SHOULD BE MORE WIDESPREAD FURTHER TO OUR NORTH. THE COLD AIR MASS
SURGING IN BEHIND THE SYSTEM MAY HAVE SOME SNOW MIXING IN WITH ANY
WRAP AROUND RAIN...ESPECIALLY TUESDAY NIGHT AND WEDNESDAY NIGHT
WHEN SURFACE TEMPERATURES ARE COOLEST. THE SYSTEM WILL FINALLY
PULL AWAY THANKSGIVING DAY INTO FRIDAY AS HIGH PRESSURE/UPPER
RIDGING BUILD IN...BRINGING A RETURN TO QUIETER AND MILDER WEATHER.
BAK
&&
.AVIATION...
ISSUED 514 PM CST SAT NOV 21 2009
VFR CONDITIONS SHOULD CONTINUE AT ALL SITES NEXT 24HRS. COULD SEE
SOME LIGHT FOG DURING THE MORNING HOURS AND HAVE INCLUDED A TEMPO
GROUP TO COVER AT ALL LOCATIONS. WINDS WILL BE EASTERLY OVERNIGHT
AND THEN BECOME MORE SOUTHEASTERLY IN THE MORNING AND THROUGHOUT
THE DAY.
AUTEN
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
000
FXUS63 KILX 212105 CCA
AFDILX
AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE LINCOLN IL
305 PM CST SAT NOV 21 2009
.DISCUSSION...
ISSUED 305 PM CST SAT NOV 21 2009
A LARGE AREA OF HIGH PRESSURE CONTINUES TO DOMINATE THE EASTERN
1/3 OF NORTH AMERICA...INCLUDING CENTRAL AND SOUTHEAST ILLINOIS.
THIS WILL CONTINUE TO BE THE CASE INTO EARLY NEXT WEEK PROVIDING
QUIET AND MILD WEATHER FOR LATE NOVEMBER. MAIN ATTENTION THIS
FORECAST PACKAGE REVOLVES AROUND A STORM SYSTEM THAT IS EXPECTED TO
DEVELOP OVER THE PLAINS ON MONDAY. THIS SYSTEM WILL PUSH THROUGH THE
FORECAST AREA TUESDAY WITH AN ASSOCIATED RISK OF RAIN. MUCH COOLER
TEMPERATURES...AND POSSIBLY SOME WRAP AROUND LIGHT RAIN/SNOW...ARE
EXPECTED IN THE WAKE OF THE SYSTEM.
12Z FORECAST GUIDANCE IS STARTING TO COME TO A CONSENSUS ON THE
TIMING OF TUESDAY/S SYSTEM AFTER QUITE A BIT OF FLIP-FLOP AND
SPREAD OVER THE PAST SEVERAL RUNS. HOPEFULLY...THIS TREND
CONTINUES AND IS NOT A ONE MODEL RUN FLUKE. HAVE TRIED TO FOLLOW A
SOLUTION THAT IS IN THE MIDDLE OF THIS CLOSER MODEL SPREAD...WHICH
PROBABLY MOST CLOSELY RESEMBLES THE NAM OR SREF SOLUTION.
HOWEVER...NONE OF THE SOLUTIONS WOULD HAVE A TREMENDOUSLY DIFFERENT
OUTCOME AT THIS TIME.
SHORT TERM...TONIGHT THROUGH TUESDAY...QUIET AND MILD WEATHER IS
EXPECTED TO PERSIST THROUGH MONDAY AS THE SURFACE HIGH DRIFTS OFF
TO THE EAST AND RETURN FLOW INCREASES. ALOFT...A SPLIT FLOW...WITH
RELATIVELY WEAK FLOW OVERHEAD IS EXPECTED INTO MONDAY. DO NOT
EXPECT FOG TO BE MUCH OF A CONCERN THE NEXT TWO NIGHTS DESPITE
LIGHT WINDS AND PARTLY CLOUDY SKIES. THERE WAS NOT MUCH FOG THIS
MORNING...AND THE LOW LEVELS/SURFACE SOILS HAVE LIKELY DRIED A BIT
MORE WITH A FULL DAY OF INSOLATION.
A VIGOROUS UPPER WAVE IS EXPECTED TO DIG INTO THE CENTRAL PLAINS
ON MONDAY...WITH ASSOCIATED SURFACE CYCLOGENESIS. A LEAD SHORT
WAVE WILL EJECT ACROSS THE MIDWEST AS THE MAIN WAVE DIGS IN...BUT
MOISTURE PROFILES APPEAR TOO SHALLOW TO PRODUCE MUCH MORE THAN
CLOUDS WITH THE LEAD WAVE. THE MAIN SURFACE LOW WILL LIFT INTO THE
GREAT LAKES BY TUESDAY NIGHT...WITH THE TRAILING COLD FRONT
EXPECTED TO CLEAR THE FORECAST AREA BY AROUND 00Z WEDNESDAY. THIS
SYSTEM SHOULD BE PRETTY DYNAMIC...THOUGH ALREADY OCCLUDED BY THE
TIME IT GETS HERE...WITH DECENT JET FORCING PROGGED OVER THE
FORECAST AREA ON TUESDAY COUPLED WITH THE SURFACE FROPA. HAVE
BUMPED UP WESTERN HALF OF THE FORECAST AREA TO LIKELY RAIN CHANCES
FOR TUESDAY...WITH THE EASTERN HALF PROBABLY NEEDING A BUMP AS
WELL ONCE THE TIMING IS MORE FIRM.
LONG TERM...TUESDAY NIGHT THROUGH SATURDAY...A SECONDARY SHORT
WAVE IS PROGGED TO DIG INTO THE MEAN UPPER TROF CENTERED OVER THE
UPPER MIDWEST/GREAT LAKES ON WEDNESDAY. THIS WAVE MAY SPREAD SOME
WRAP AROUND PRECIPITATION INTO THE FORECAST AREA...THOUGH IT
SHOULD BE MORE WIDESPREAD FURTHER TO OUR NORTH. THE COLD AIR MASS
SURGING IN BEHIND THE SYSTEM MAY HAVE SOME SNOW MIXING IN WITH ANY
WRAP AROUND RAIN...ESPECIALLY TUESDAY NIGHT AND WEDNESDAY NIGHT
WHEN SURFACE TEMPERATURES ARE COOLEST. THE SYSTEM WILL FINALLY
PULL AWAY THANKSGIVING DAY INTO FRIDAY AS HIGH PRESSURE/UPPER
RIDGING BUILD IN...BRINGING A RETURN TO QUIETER AND MILDER WEATHER.
BAK
&&
.AVIATION...
ISSUED 1143 AM CST SAT NOV 21 2009
A STORM SYSTEM OVER TEXAS CONTINUES TO PUSH MID-LEVEL MOISTURE
NORTHWARD ACROSS WESTERN ILLINOIS. LATEST SATELLITE IMAGERY
INDICATES SCT-BKN CLOUDS WITH BASES AROUND 7000FT ALONG AND WEST
OF I-55...WITH CLEAR SKIES FURTHER EAST. CLOUDS WILL TEND TO
DISSOLVE AS THEY TRY TO MOVE NORTHEASTWARD INTO A DRIER AIR MASS
BENEATH SURFACE HIGH PRESSURE CENTERED OVER INDIANA. AS A
RESULT...WILL ONLY CARRY SCT CLOUDS AT KCMI AND KDEC. FURTHER
WEST...WILL MAINTAIN BKN MID-DECK AT KPIA AND KSPI THROUGH THE
AFTERNOON INTO THE EVENING. 12Z NAM-WRF AND GFS RH PROFILES
INDICATE A DRYING TREND OVERNIGHT...SO WILL SCATTER OUT THE CLOUDS
ACROSS THE WESTERN TERMINALS BETWEEN 05Z AND 06Z. WINDS THROUGH
THE ENTIRE 18Z TAF PERIOD WILL REMAIN LIGHT OUT OF THE E/SE.
BARNES
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
000
FXUS63 KILX 212100
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
300 PM CST SAT NOV 21 2009
.DISCUSSION...
ISSUED 300 PM CST SAT NOV 21 2009
A LARGE AREA OF HIGH PRESSURE CONTINUES TO DOMINATE THE EASTERN
1/3 OF NORTH AMERICA...INCLUDING CENTRAL AND SOUTHEAST ILLINOIS.
THIS WILL CONTINUE TO BE THE CASE INTO EARLY NEXT WEEK PROVIDING
QUIET AND WEATHER FOR LATE NOVEMBER. MAIN ATTENTION THIS FORECAST
PACKAGE REVOLVES AROUND A STORM SYSTEM THAT IS EXPECTED TO DEVELOP
OVER THE PLAINS ON MONDAY. THIS SYSTEM WILL PUSH THROUGH THE
FORECAST AREA TUESDAY WITH AN ASSOCIATED RISK OF RAIN. MUCH COOLER
TEMPERATURES...AND POSSIBLY SOME WRAP AROUND LIGHT RAIN/SNOW IN
THE WAKE OF THE SYSTEM.
12Z FORECAST GUIDANCE IS STARTING TO COME TO A CONSENSUS ON THE
TIMING OF TUESDAY/S SYSTEM AFTER QUITE A BIT OF FLIP-FLOP AND
SPREAD OVER THE PAST SEVERAL RUNS. HOPEFULLY...THIS TREND
CONTINUES AND IS NOT A ONE MODEL RUN FLUKE. HAVE TRIED TO FOLLOW A
SOLUTION THAT IS IN THE MIDDLE OF THIS CLOSER MODEL SPREAD...WHICH
PROBABLY MOST CLOSELY RESEMBLES THE NAM OR SREF SOLUTION.
HOWEVER...NONE OF THE SOLUTIONS WOULD HAVE A TREMENDOUSLY DIFFERENT
OUTCOME AT THIS TIME.
SHORT TERM...TONIGHT THROUGH TUESDAY...QUIET AND MILD WEATHER IS
EXPECTED TO PERSIST THROUGH MONDAY AS THE SURFACE HIGH DRIFTS OFF
TO THE EAST AND RETURN FLOW INCREASES. ALOFT...A SPLIT FLOW...WITH
RELATIVELY WEAK FLOW OVERHEAD IS EXPECTED INTO MONDAY. DO NOT
EXPECT FOG TO BE MUCH OF A CONCERN THE NEXT TWO NIGHTS DESPITE
LIGHT WINDS AND PARTLY CLOUDY SKIES. THERE WAS NOT MUCH FOG THIS
MORNING...AND THE LOW LEVELS/SURFACE SOILS HAVE LIKELY DRIED A BIT
MORE WITH A FULL DAY OF INSOLATION.
A VIGOROUS UPPER WAVE IS EXPECTED TO DIG INTO THE CENTRAL PLAINS
ON MONDAY...WITH ASSOCIATED SURFACE CYCLOGENESIS. A LEAD SHORT
WAVE WILL EJECT ACROSS THE MIDWEST AS THE MAIN WAVE DIGS IN...BUT
MOISTURE PROFILES APPEAR TOO SHALLOW TO PRODUCE MUCH MORE THAN
CLOUDS WITH THE LEAD WAVE. THE MAIN SURFACE LOW WILL LIFT INTO THE
GREAT LAKES BY TUESDAY NIGHT...WITH THE TRAILING COLD FRONT
EXPECTED TO CLEAR THE FORECAST AREA BY AROUND 00Z WEDNESDAY. THIS
SYSTEM SHOULD BE PRETTY DYNAMIC...THOUGH ALREADY OCCLUDED BY THE
TIME IT GETS HERE...WITH DECENT JET FORCING PROGGED OVER THE
FORECAST AREA ON TUESDAY COUPLED WITH THE SURFACE FROPA. HAVE
BUMPED UP WESTERN HALF OF THE FORECAST AREA TO LIKELY RAIN CHANCES
FOR TUESDAY...WITH THE EASTERN HALF PROBABLY NEEDING A BUMP AS
WELL ONCE THE TIMING IS MORE FIRM.
LONG TERM...TUESDAY NIGHT THROUGH SATURDAY...A SECONDARY SHORT
WAVE IS PROGGED TO DIG INTO THE MEAN UPPER TROF CENTERED OVER THE
UPPER MIDWEST/GREAT LAKES ON WEDNESDAY. THIS WAVE MAY SPREAD SOME
WRAP AROUND PRECIPITATION INTO THE FORECAST AREA...THOUGH IT
SHOULD BE MORE WIDESPREAD FURTHER TO OUR NORTH. THE COLD AIR MASS
SURGING IN BEHIND THE SYSTEM MAY HAVE SOME SNOW MIXING IN WITH ANY
WRAP AROUND RAIN...ESPECIALLY TUESDAY NIGHT AND WEDNESDAY NIGHT
WHEN SURFACE TEMPERATURES ARE COOLEST. THE SYSTEM WILL FINALLY
PULL AWAY THANKSGIVING DAY INTO FRIDAY AS HIGH PRESSURE/UPPER
RIDGING BUILD IN...BRINGING A RETURN TO QUIETER AND MILDER WEATHER.
BAK
&&
.AVIATION...
ISSUED 1143 AM CST SAT NOV 21 2009
A STORM SYSTEM OVER TEXAS CONTINUES TO PUSH MID-LEVEL MOISTURE
NORTHWARD ACROSS WESTERN ILLINOIS. LATEST SATELLITE IMAGERY
INDICATES SCT-BKN CLOUDS WITH BASES AROUND 7000FT ALONG AND WEST
OF I-55...WITH CLEAR SKIES FURTHER EAST. CLOUDS WILL TEND TO
DISSOLVE AS THEY TRY TO MOVE NORTHEASTWARD INTO A DRIER AIR MASS
BENEATH SURFACE HIGH PRESSURE CENTERED OVER INDIANA. AS A
RESULT...WILL ONLY CARRY SCT CLOUDS AT KCMI AND KDEC. FURTHER
WEST...WILL MAINTAIN BKN MID-DECK AT KPIA AND KSPI THROUGH THE
AFTERNOON INTO THE EVENING. 12Z NAM-WRF AND GFS RH PROFILES
INDICATE A DRYING TREND OVERNIGHT...SO WILL SCATTER OUT THE CLOUDS
ACROSS THE WESTERN TERMINALS BETWEEN 05Z AND 06Z. WINDS THROUGH
THE ENTIRE 18Z TAF PERIOD WILL REMAIN LIGHT OUT OF THE E/SE.
BARNES
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
000
FXUS63 KLOT 212031
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
231 PM CST SAT NOV 21 2009
.DISCUSSION...
230 PM CST
NOT MUCH CHANGE IN CONCERNS FROM THIS MRNG. FOG POTENTIAL STILL
LOOMS TONIGHT DESPITE PASSING AC ADVECTION NWD THRU WRN IL. DEWPTS
STILL NR 40 TNGT AND WITH CALM WINDS AND NEARLY CLEAR SKIES...VSBYS
SHUD START LOWERING AFTER MDNGT AND PROGRESS TOWARD ZERO NR SUNRISE.
AC PASSAGE NWD THRU WESTERN IL WILL LIKELY KEEP VSBY UP ABV ADVISORY
CRITERIA FOR SECTIONS WEST OF I-39.
THIS PASSING AC TO CONTINUE THRU MONDAY AND PROMPT PARTLY CLOUDY
CONDITIONS UNTIL MONDAY NIGHT. WHILE MAX TEMPS TRY TO WARM UP EARLY
IN THE WEEK UNDER INCREASING SW FLOW ALOFT...INCREASED CLOUD COVER
AND LOWER SUN ANGLE WILL INHIBIT THE USUAL TEMP JUMPS ASSOCIATED
WITH EARLY AUTUMN WARM AIR ADVECTION...BUT RESPOND READILY TO ANY
UPCOMING COLD AIR ADVECTION. THUS HIGHS EARLY THIS WEEK WILL HOVER
IN THE 50S BUT SETTLE INTO THE 40S AFTER TUESDAY.
TUESDAY THEN IS THE FOCUS OF NEXT CONCERN. THE UPR LVL PATTERN
ASSOCIATED WITH THIS UPCOMING CHANGE HASNT EVEN MADE IT ONTO THE
WEST COAST AS YET...BUT SHUD BE MAKING LANDFALL LATE TONIGHT AND
CROSSING THE NRN ROCKIES SUNDAY NIGHT. DEEPENING MONDAY INTO A
STRONG CLOSED LOW IN THE PLAINS...EXPECT TO SEE AC AND CI ADVECTING
INTO THE MS VLY AND PCPN CHANCES INCREASE THU ILLINOIS LATE MON NGT
INTO TUESDAY.
ALL MODELS ARE TRENDING TOWARD OCCLUDING THIS SYSTEM FROM THE MID
AND UPR MS VLY TO THE GREAT LAKES BY MIDWEEK. TIMING AND STORM
CENTER LOCATION DIFFERENCES ARE STILL APPARENT AMONG THEM. THE ECMWF
IS CONSIDERABLY SLOWER THAN THE GFS AND NAM WITH THE NAM BEARING A
MORE SLY TRACK THAN EITHER OF THE TWO. AT THIS POINT...A BLEND IS
PROBABLY PRUDENT. THE GENERAL TREND THO IS FOR RAIN TO BEGIN TUESDAY
WITH COLD AIR WRAPAROUND FILTERING IN WEDNESDAY AND MIXING WITH
SNOW WED NIGHT BEFORE DIMINISHING TO SCATTERED FLURRIES THURSDAY.
GFS AND ECMWF ACTUALLY RESOLVE TWO DISTINCT CLOSED UPR TROFS
SWINGING THRU LATE IN THE WEEK. THE FIRST TROF ASSOCIATED WITH THE
RAIN ONSET ON TUESDAY SHUD SWING THRU ON WEDNESDAY. WEAK UPR
RIDGING MAY PUT AN END TO THE RAIN WED AFTN BEFORE A SECONDARY
CLIPPER-LIKE SYSTEM SWINGS DOWN FROM MANITOBA TO NRN IL WED NGT.
THE SECOND SHOT OF CAA FOLLOWING THIS SECOND TROF PASSAGE WILL BE
THE IMPULSE THAT PULLS DOWN AIR COLD ENUF TO CHANGEOVER TO A SNOW
MIXTURE. UPR RIDGING WORKING IN FRIDAY AND SATURDAY WILL END ANY
LINGERING FLURRIE CHANCES WHILE RETURNING WARM AIR ADVECTION FOR
THE WEEKEND.
RLB
&&
.AVIATION...
1800 UTC TAFS...HIGH PRESSURE WILL REMAIN ANCHORED OVER THE REGION
THROUGH THE NEXT 24-30 HOURS. CLOSE PROXIMITY OF THE HIGH WILL
KEEP WINDS CALM TO VERY LIGHT AND MAINLY SOUTHEASTERLY. RETURN
FLOW ALOFT IS SENDING A BIT OF HIGH BASED STRATUS/LOW BASED ALTO
CUMULUS NORTHWARD INTO THE MID MISSISSIPPI VALLEY THIS AFTERNOON.
SOME OF THIS CLOUDINESS WILL SPILL EASTWARD OVER THE TERMINALS
TONIGHT...PARTICULARLY OUT WEST TOWARD RFD.
DESPITE THE CLOUDINESS...LIGHT WINDS AND STAGNANT AIR MASS WILL
ONCE AGAIN FAVOR THE DEVELOPMENT OF PATCHY GROUND FOG TONIGHT.
EVEN WITH FAIRLY EXTENSIVE CLOUDINESS OVER MISSOURI LAST
NIGHT...FOG WAS STILL FAIRLY PREVALENT...SO EVEN WITH POTENTIAL
FOR SCT-BKN VFR DECK TONIGHT HAVE CONTINUED TO INCLUDED REDUCED
VSBYS IN MAINLY LIGHT/SHALLOW FOG. DPA APPEARS TO HAVE HIGHEST
PROBS OF BOTTOMING OUT WITH VSBY IFR OR LOWER...THOUGH A PERIOD OF
IFR VSBYS ARE EVEN POSSIBLE CLOSER TO URBAN HEAT ISLAND NEAR
ORD/MDW. MUCH LIKE TODAY...VSBYS WILL LIKELY BE SOMEWHAT SLOW TO
CLIMB ABOVE MVFR WITH STAGNANT AIRMASS ALLOWING FOR LIGHT FOG TO
TRANSITION TO LINGERING HAZINESS.
IZZI
&&
.MARINE...
145 PM CST
NO SIGNIFICANT WINDS/WAVE EXPECTED THROUGH THE NEXT SEVERAL DAYS
WITH HIGH PRESSURE IN CONTROL OF THE WEATHER. LIGHT/VARIABLE
WINDS WILL TEND TO TURN MORE SOUTHERLY TONIGHT...ALBEIT NOT VERY
STRONGLY...AND GENERALLY CONTINUE IN A GENERAL SOUTHEASTERLY
DIRECTION THROUGH MIDWEEK.
IZZI
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&
$$
000
FXUS63 KLOT 211943
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
143 PM CST SAT NOV 21 2009
.DISCUSSION...
306 AM CST
SHORT TERM CONCERNS CENTER ON FOG POTENTIAL EARLY THIS MORNING AND
AGAIN TONIGHT. ATTENTION THEN TURNS TO MID WEEK STORM SYSTEM.
THIS MORNING...REGION REMAINS SITUATED UNDER THE CONTROL OF A
SURFACE RIDGE EXTENDING FROM MID ATLANTIC STATES WEST THROUGH
CENTRAL ILLINOIS. SKIES HAVE BEEN ABLE TO CLEAR OUT ACROSS MUCH OF
THE REGION IN THE WAKE OF A DEPARTING WEAK SHORTWAVE. AS A
RESULT...FOG HAS FORMED ACROSS MUCH OF THE AREA...WITH MANY
LOCATIONS DIPPING INTO THE 2-4 SM RANGE THIS MORNING. IT WOULD NOT
BE A SURPRISE TO SEE VIS LOWER A LITTLE MORE TOWARD SUNRISE AS
PBL CONTINUES TO COOL... AND PATCHES OF DENSE FOG WILL REMAIN
A POSSIBILITY THROUGH MID MORNING.
ONCE THE FOG DISSIPATES LATER TODAY...SHOULD SEE THE BEGINNINGS OF
A VERY NICE MID NOVEMBER WEEKEND WITH AFTERNOON HIGHS WARMING INTO
THE MID 50S ACROSS THE AREA. SCENARIO BASICALLY REPEATS ITSELF
TONIGHT AND SUNDAY...WITH PATCHY FOG AGAIN POSSIBLE LATE TONIGHT
AND SUNDAY MORNING...AND HIGHS ON SUNDAY IN THE MID TO PERHAPS
UPPER 60S.
ON MONDAY...ADVERTISED MID WEEK STORM SYSTEM WILL BE BEGINNING TO
ORGANIZE OVER THE NORTHERN HIGH PLAINS. EXPECT TO SEE MID AND HIGH
LEVEL CLOUD COVER START TO INCREASE AS WAA TAKES SHAPE ACROSS
AREAS JUST TO THE WEST OF LOT CWA. NUMERICAL GUIDANCE CONTINUES TO
STRUGGLE WITH EVOLUTION OF THIS SYSTEM...WITH ECMWF GENERALLY
SLOWER AND MORE CUTOFF FROM MAIN WESTERLIES COMPARED TO MUCH MORE
PROGRESSIVE OPERATIONAL GFS. CANADIAN AND GFS ENSEMBLES HAVE
GENERALLY BEEN SPLITTING THE DIFFERENCE...AND SEEM LIKE THE
PRUDENT SOLUTION TO FOLLOW UNTIL DETAILS BECOME LESS MUDDY. OF
NOTE...00Z EURO THAT CAME IN EARLY THIS MORNING HAS COME IN MORE
PROGRESSIVE...SEEMINGLY AT LEAST A TREND TOWARD GENERAL IDEA OF
GFS ENSEMBLE/CANADIAN.
CONFIDENCE IS STARTING TO INCREASE THAT RAIN WILL OVERSPREAD THE
AREA TUESDAY INTO WEDNESDAY AS OCCLUDING FRONT MOVES THROUGH THE
AREA. CHANCES ARE THAT A DRY SLOT OF SOME SORT WILL MOVE IN BEHIND
THIS FIRST SHOT OF RAIN...BUT ATTEMPTING TO DETERMINE SPECIFICS OF
SUCH A DETAIL AT THIS TIME IS ALL BUT IMPOSSIBLE. ADDITIONAL
PRECIPITATION WILL BE POSSIBLE WEDNESDAY AND THURSDAY AS MAIN
UPPER TROUGH AXIS...AND PERHAPS SECONDARY COLD FRONT...PUSHES
THROUGH. PRECIP TYPE CERTAINLY IN QUESTION WEDNESDAY NIGHT ONWARD
AS GFS IS TRENDING COLDER THAN EURO. SPECIFICS OF RAIN VS SNOW
WILL BE ENTIRELY DEPENDENT ON EXACT TRACK AND STRENGTH OF UPPER
TROUGH. AT THIS TIME...DECIDED TO CHANGE LITTLE IN THE WAY OF
INHERITED PRECIP TYPE TO AVOID POTENTIAL FLIP FLOPS IN LATER
FORECASTS.
BOXELL
&&
.AVIATION...
1800 UTC TAFS...HIGH PRESSURE WILL REMAIN ANCHORED OVER THE REGION
THROUGH THE NEXT 24-30 HOURS. CLOSE PROXIMITY OF THE HIGH WILL
KEEP WINDS CALM TO VERY LIGHT AND MAINLY SOUTHEASTERLY. RETURN
FLOW ALOFT IS SENDING A BIT OF HIGH BASED STRATUS/LOW BASED ALTO
CUMULUS NORTHWARD INTO THE MID MISSISSIPPI VALLEY THIS AFTERNOON.
SOME OF THIS CLOUDINESS WILL SPILL EASTWARD OVER THE TERMINALS
TONIGHT...PARTICULARLY OUT WEST TOWARD RFD.
DESPITE THE CLOUDINESS...LIGHT WINDS AND STAGNANT AIR MASS WILL
ONCE AGAIN FAVOR THE DEVELOPMENT OF PATCHY GROUND FOG TONIGHT.
EVEN WITH FAIRLY EXTENSIVE CLOUDINESS OVER MISSOURI LAST
NIGHT...FOG WAS STILL FAIRLY PREVALENT...SO EVEN WITH POTENTIAL
FOR SCT-BKN VFR DECK TONIGHT HAVE CONTINUED TO INCLUDED REDUCED
VSBYS IN MAINLY LIGHT/SHALLOW FOG. DPA APPEARS TO HAVE HIGHEST
PROBS OF BOTTOMING OUT WITH VSBY IFR OR LOWER...THOUGH A PERIOD OF
IFR VSBYS ARE EVEN POSSIBLE CLOSER TO URBAN HEAT ISLAND NEAR
ORD/MDW. MUCH LIKE TODAY...VSBYS WILL LIKELY BE SOMEWHAT SLOW TO
CLIMB ABOVE MVFR WITH STAGNANT AIRMASS ALLOWING FOR LIGHT FOG TO
TRANSITION TO LINGERING HAZINESS.
IZZI
&&
.MARINE...
145 PM CST
NO SIGNIFICANT WINDS/WAVE EXPECTED THROUGH THE NEXT SEVERAL DAYS
WITH HIGH PRESSURE IN CONTROL OF THE WEATHER. LIGHT/VARIABLE
WINDS WILL TEND TO TURN MORE SOUTHERLY TONIGHT...ALBEIT NOT VERY
STRONGLY...AND GENERALLY CONTINUE IN A GENERAL SOUTHEASTERLY
DIRECTION THROUGH MIDWEEK.
IZZI
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&
$$
000
FXUS63 KILX 211743
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1143 AM CST SAT NOV 21 2009
.DISCUSSION...
ISSUED 1042 AM CST SAT NOV 21 2009
MOISTURE CONTINUES TO SPREAD NORTHWARD FROM A STORM SYSTEM OVER
EASTERN TEXAS. LATEST SATELLITE IMAGERY INDICATES PARTLY TO MOSTLY
CLOUDY CONDITIONS ALONG AND WEST OF I-55...WITH SUNNY SKIES FURTHER
EAST. BASED ON GENERAL N/NE DRIFT OF CLOUD COVER AND DRIER AIRMASS
POISED TO THE EAST...THINK ABUNDANT SUNSHINE WILL PREVAIL ACROSS
THE E/SE KILX CWA FOR THE BALANCE OF THE DAY. MEANWHILE...QUITE A
BIT OF CLOUD COVER WILL CONTINUE TO PLAGUE LOCATIONS FROM I-55
WEST. HAVE UPDATED FORECAST TO BETTER REFLECT SKY TREND AND TO
LOWER HIGH TEMPS BY A COUPLE OF DEGREES ACROSS THE ILLINOIS RIVER
VALLEY. SHOULD SEE AFTERNOON HIGHS RANGING FROM THE MIDDLE 50S
WEST OF THE ILLINOIS RIVER...TO THE LOWER 60S SOUTH OF I-70.
&&
.AVIATION...
ISSUED 1143 AM CST SAT NOV 21 2009
A STORM SYSTEM OVER TEXAS CONTINUES TO PUSH MID-LEVEL MOISTURE
NORTHWARD ACROSS WESTERN ILLINOIS. LATEST SATELLITE IMAGERY
INDICATES SCT-BKN CLOUDS WITH BASES AROUND 7000FT ALONG AND WEST
OF I-55...WITH CLEAR SKIES FURTHER EAST. CLOUDS WILL TEND TO
DISSOLVE AS THEY TRY TO MOVE NORTHEASTWARD INTO A DRIER AIRMASS
BENEATH SURFACE HIGH PRESSURE CENTERED OVER INDIANA. AS A
RESULT...WILL ONLY CARRY SCT CLOUDS AT KCMI AND KDEC. FURTHER
WEST...WILL MAINTAIN BKN MID-DECK AT KPIA AND KSPI THROUGH THE
AFTERNOON INTO THE EVENING. 12Z NAM-WRF AND GFS RH PROFILES
INDICATE A DRYING TREND OVERNIGHT...SO WILL SCATTER OUT THE CLOUDS
ACROSS THE WESTERN TERMINALS BETWEEN 05Z AND 06Z. WINDS THROUGH
THE ENTIRE 18Z TAF PERIOD WILL REMAIN LIGHT OUT OF THE E/SE.
BARNES
&&
.PREV DISCUSSION...
ISSUED 205 AM CST SAT NOV 21 2009
LATEST SURFACE MAP SHOWING THE CWA UNDERNEATH AN EAST-WEST HIGH
PRESSURE RIDGE...CENTERED IN SOUTHEAST OHIO. SATELLITE FOG
IMAGERY SHOWING PATCHES OF STRATOCUMULUS CLOUDS ACROSS THE EAST
CENTRAL CWA AROUND CHAMPAIGN AND DANVILLE...AS WELL AS SCATTERED
NEAR THE ST LOUIS AREA. DENSE FOG HAS MAINLY BEEN PATCHY THUS
FAR...WITH AVERAGE VISIBILITIES OVER THE CWA IN THE 3 TO 7 MILE
RANGE.
MAIN SHORT TERM CONCERN INVOLVES THE FOG THIS MORNING. IN THE
LONGER RANGE...EVOLUTION OF THE NEXT STORM SYSTEM IN THE TUESDAY-
WEDNESDAY TIME FRAME IS THE PRIMARY FORECAST CONCERN.
SHORT TERM...TODAY THROUGH MONDAY...
THE FOG HAS BEEN SLOWER TO EVOLVE THAN LAST NIGHT...BUT LATEST
SURFACE PLOT SHOWING FOG BECOMING MORE WIDESPREAD ACROSS IOWA AND
ADJACENT AREAS OF MISSOURI AND ILLINOIS. RUC MODEL SUPPORTS SOME
EXPANSION OF THIS AREA...AND WILL KEEP THE DENSE FOG ADVISORY
GOING ACROSS THE NORTHERN CWA. ACROSS THE SOUTH...BELIEVE THE FOG
WILL BE MORE PATCHY IN NATURE...DUE TO THE DRYING THAT TOOK PLACE
IN THE SUNSHINE ON FRIDAY.
OTHER THAN THAT...MODELS IN DECENT AGREEMENT THROUGH MONDAY...
KEEPING THINGS DRY. TEMPERATURES EXPECTED TO REMAIN SEVERAL
DEGREES ABOVE NORMAL. MET/MAV MOS GUIDANCE FAIRLY CLOSE AND DID
NOT SIGNIFICANTLY DEVIATE FROM IT.
LONG TERM...TUESDAY THROUGH FRIDAY...
MAIN FORECAST CHALLENGE INVOLVES EVOLUTION OF UPPER TROUGH THAT
WILL MOVE INTO THE PACIFIC NORTHWEST ON SUNDAY. THE MAJOR MODELS
ALL HAVE A CLOSED CIRCULATION DEVELOPING OVER THE CENTRAL PLAINS
BY TUESDAY MORNING...BUT THE SPEED AND TRACK OF THE SURFACE
FEATURES REMAIN IN QUESTION. GFS HAS SLOWED A BIT BUT CONTINUES TO
BE THE FASTER OF THE EXTENDED MODELS...BRINGING THE COLD FRONT
THROUGH THE CWA BY ABOUT MIDDAY TUESDAY AND HAVING WRAPAROUND
PRECIP AFFECTING THE AREA TUESDAY NIGHT. MEANWHILE...THE ECMWF
PLACES THE SURFACE LOW IN SOUTHEAST NEBRASKA AT 12Z TUESDAY AND
MOVES IT TO NEAR ROCKFORD BY 12Z WEDNESDAY...WITH THE SURFACE
FRONT PASSING THROUGH OUR AREA SHORTLY AFTERWARD. TRENDED TOWARD
THE SLOWER SOLUTION AND THUS REDUCED POPS TO SLIGHT CHANCE ACROSS
THE EASTERN CWA MONDAY NIGHT. WENT AHEAD AND ADDED SOME LOW CHANCE
POPS TUESDAY NIGHT AND WEDNESDAY ACROSS THE NORTH...AS THAT AREA
SHOULD AT LEAST BE GETTING SOME WRAPAROUND PRECIPITATION FROM THE
GFS SOLUTION...OR FROM THE FRONT ITSELF IN THE ECMWF SOLUTION.
SOUTHERN CWA IS NOT AS CLEAR CUT AT THIS TIME...AND WILL NOT
CHANGE THE POPS IN THAT AREA. UNTIL MORE CONSISTENCY DEVELOPS.
1000-500MB THICKNESS...AS WELL AS BUFKIT SOUNDINGS...WOULD SUGGEST
THAT PRECIP TYPE WOULD BE A CONCERN AS WELL. CURRENTLY PLAN TO
LIMIT ANY MIXED PRECIP TO THE FAR NORTHERN CWA FOR TUESDAY NIGHT.
BOTH MODELS SHOWING WEAK TROUGHS MOVING THROUGH ON THANKSGIVING
DAY...FOLLOWED BY HIGH PRESSURE RIDGING BUILDING IN FROM THE WEST.
HOWEVER...NO CHANGES WERE MADE TO THIS PORTION OF THE FORECAST.
GEELHART
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
000
FXUS63 KLOT 211718
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1118 AM CST SAT NOV 21 2009
.DISCUSSION...
306 AM CST
SHORT TERM CONCERNS CENTER ON FOG POTENTIAL EARLY THIS MORNING AND
AGAIN TONIGHT. ATTENTION THEN TURNS TO MID WEEK STORM SYSTEM.
THIS MORNING...REGION REMAINS SITUATED UNDER THE CONTROL OF A
SURFACE RIDGE EXTENDING FROM MID ATLANTIC STATES WEST THROUGH
CENTRAL ILLINOIS. SKIES HAVE BEEN ABLE TO CLEAR OUT ACROSS MUCH OF
THE REGION IN THE WAKE OF A DEPARTING WEAK SHORTWAVE. AS A
RESULT...FOG HAS FORMED ACROSS MUCH OF THE AREA...WITH MANY
LOCATIONS DIPPING INTO THE 2-4 SM RANGE THIS MORNING. IT WOULD NOT
BE A SURPRISE TO SEE VIS LOWER A LITTLE MORE TOWARD SUNRISE AS
PBL CONTINUES TO COOL... AND PATCHES OF DENSE FOG WILL REMAIN
A POSSIBILITY THROUGH MID MORNING.
ONCE THE FOG DISSIPATES LATER TODAY...SHOULD SEE THE BEGINNINGS OF
A VERY NICE MID NOVEMBER WEEKEND WITH AFTERNOON HIGHS WARMING INTO
THE MID 50S ACROSS THE AREA. SCENARIO BASICALLY REPEATS ITSELF
TONIGHT AND SUNDAY...WITH PATCHY FOG AGAIN POSSIBLE LATE TONIGHT
AND SUNDAY MORNING...AND HIGHS ON SUNDAY IN THE MID TO PERHAPS
UPPER 60S.
ON MONDAY...ADVERTISED MID WEEK STORM SYSTEM WILL BE BEGINNING TO
ORGANIZE OVER THE NORTHERN HIGH PLAINS. EXPECT TO SEE MID AND HIGH
LEVEL CLOUD COVER START TO INCREASE AS WAA TAKES SHAPE ACROSS
AREAS JUST TO THE WEST OF LOT CWA. NUMERICAL GUIDANCE CONTINUES TO
STRUGGLE WITH EVOLUTION OF THIS SYSTEM...WITH ECMWF GENERALLY
SLOWER AND MORE CUTOFF FROM MAIN WESTERLIES COMPARED TO MUCH MORE
PROGRESSIVE OPERATIONAL GFS. CANADIAN AND GFS ENSEMBLES HAVE
GENERALLY BEEN SPLITTING THE DIFFERENCE...AND SEEM LIKE THE
PRUDENT SOLUTION TO FOLLOW UNTIL DETAILS BECOME LESS MUDDY. OF
NOTE...00Z EURO THAT CAME IN EARLY THIS MORNING HAS COME IN MORE
PROGRESSIVE...SEEMINGLY AT LEAST A TREND TOWARD GENERAL IDEA OF
GFS ENSEMBLE/CANADIAN.
CONFIDENCE IS STARTING TO INCREASE THAT RAIN WILL OVERSPREAD THE
AREA TUESDAY INTO WEDNESDAY AS OCCLUDING FRONT MOVES THROUGH THE
AREA. CHANCES ARE THAT A DRY SLOT OF SOME SORT WILL MOVE IN BEHIND
THIS FIRST SHOT OF RAIN...BUT ATTEMPTING TO DETERMINE SPECIFICS OF
SUCH A DETAIL AT THIS TIME IS ALL BUT IMPOSSIBLE. ADDITIONAL
PRECIPITATION WILL BE POSSIBLE WEDNESDAY AND THURSDAY AS MAIN
UPPER TROUGH AXIS...AND PERHAPS SECONDARY COLD FRONT...PUSHES
THROUGH. PRECIP TYPE CERTAINLY IN QUESTION WEDNESDAY NIGHT ONWARD
AS GFS IS TRENDING COLDER THAN EURO. SPECIFICS OF RAIN VS SNOW
WILL BE ENTIRELY DEPENDENT ON EXACT TRACK AND STRENGTH OF UPPER
TROUGH. AT THIS TIME...DECIDED TO CHANGE LITTLE IN THE WAY OF
INHERITED PRECIP TYPE TO AVOID POTENTIAL FLIP FLOPS IN LATER
FORECASTS.
BOXELL
&&
.AVIATION...
1800 UTC TAFS...HIGH PRESSURE WILL REMAIN ANCHORED OVER THE REGION
THROUGH THE NEXT 24-30 HOURS. CLOSE PROXIMITY OF THE HIGH WILL
KEEP WINDS CALM TO VERY LIGHT AND MAINLY SOUTHEASTERLY. RETURN
FLOW ALOFT IS SENDING A BIT OF HIGH BASED STRATUS/LOW BASED ALTO
CUMULUS NORTHWARD INTO THE MID MISSISSIPPI VALLEY THIS AFTERNOON.
SOME OF THIS CLOUDINESS WILL SPILL EASTWARD OVER THE TERMINALS
TONIGHT...PARTICULARLY OUT WEST TOWARD RFD.
DESPITE THE CLOUDINESS...LIGHT WINDS AND STAGNANT AIR MASS WILL
ONCE AGAIN FAVOR THE DEVELOPMENT OF PATCHY GROUND FOG TONIGHT.
EVEN WITH FAIRLY EXTENSIVE CLOUDINESS OVER MISSOURI LAST
NIGHT...FOG WAS STILL FAIRLY PREVALENT...SO EVEN WITH POTENTIAL
FOR SCT-BKN VFR DECK TONIGHT HAVE CONTINUED TO INCLUDED REDUCED
VSBYS IN MAINLY LIGHT/SHALLOW FOG. DPA APPEARS TO HAVE HIGHEST
PROBS OF BOTTOMING OUT WITH VSBY IFR OR LOWER...THOUGH A PERIOD OF
IFR VSBYS ARE EVEN POSSIBLE CLOSER TO URBAN HEAT ISLAND NEAR
ORD/MDW. MUCH LIKE TODAY...VSBYS WILL LIKELY BE SOMEWHAT SLOW TO
CLIMB ABOVE MVFR WITH STAGNANT AIRMASS ALLOWING FOR LIGHT FOG TO
TRANSITION TO LINGERING HAZINESS.
IZZI
&&
.MARINE...
306 AM CST
OVERALL VERY FEW CHANGES MADE TO THE NEARSHORE AND OPEN WATERS
FORECAST. A BROAD SURFACE ANTICYCLONE STRETCHING FROM NORTHERN
ILLINOIS TO WEST VIRGINIA WILL CONTINUE TO SLOWLY SLIDE EAST OF THE
AREA SETTING UP A LIGHT SOUTH WIND OVER LAKE MICHIGAN FOR THIS
AFTERNOON. UPPER LEVEL RIDGING IS EXPECTED TO PERSIST ACROSS
SOUTHEAST CANADA/NORTHEAST UNITED STATES OVER NEXT FEW DAYS WHICH
WILL ALLOW SOME WEAK SURFACE RIDGING TO HANG BACK ACROSS THE GREAT
LAKES REGION. THUS...DESPITE MAIN SURFACE ANTICYCLONE SHIFTING EAST
NORTHEAST NEXT FEW DAYS...GRADIENT WILL BE SLOW TO STRENGTHEN...SO
MODEST SOUTH WIND SPEED INCREASES INTO THE 10 TO 15 KT RANGE STILL
SEEMS REASONABLE BY SUNDAY. A FAIRLY STRONG UPPER LEVEL TROUGH WILL
MOVE INTO THE CENTRAL PLAINS MONDAY NIGHT/TUESDAY WITH NEXT SFC LOW
TAKING SHAPE ACROSS THE CENTRAL PLAINS. THIS LOW WILL APPROACH THE
WESTERN GREAT LAKES BY WEDNESDAY. THE EXPECTED TRACK OF THIS LOW
WOULD SUPPORT CONTINUED SOUTH SOUTHEAST WINDS THROUGH MIDDLE OF NEXT
WEEK. WHILE SPEEDS ARE EXPECTED TO GENERALLY REMAIN IN THE 10 TO 20
KNOT RANGE...THE EXTENDED SOUTH SOUTHEAST FETCH COULD ALLOW WAVE
HEIGHTS TO BUILD INTO THE 3 TO 5 FT RANGE TOWARD THE END OF THE
FORECAST PERIOD LATE TUESDAY NIGHT INTO WEDNESDAY.
MARSILI
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&
$$
000
FXUS63 KILX 211642
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1042 AM CST SAT NOV 21 2009
.DISCUSSION...
ISSUED 1042 AM CST SAT NOV 21 2009
MOISTURE CONTINUES TO SPREAD NORTHWARD FROM A STORM SYSTEM OVER
EASTERN TEXAS. LATEST SATELLITE IMAGERY INDICATES PARTLY TO MOSTLY
CLOUDY CONDITIONS ALONG AND WEST OF I-55...WITH SUNNY SKIES FURTHER
EAST. BASED ON GENERAL N/NE DRIFT OF CLOUD COVER AND DRIER AIRMASS
POISED TO THE EAST...THINK ABUNDANT SUNSHINE WILL PREVAIL ACROSS
THE E/SE KILX CWA FOR THE BALANCE OF THE DAY. MEANWHILE...QUITE A
BIT OF CLOUD COVER WILL CONTINUE TO PLAGUE LOCATIONS FROM I-55
WEST. HAVE UPDATED FORECAST TO BETTER REFLECT SKY TREND AND TO
LOWER HIGH TEMPS BY A COUPLE OF DEGREES ACROSS THE ILLINOIS RIVER
VALLEY. SHOULD SEE AFTERNOON HIGHS RANGING FROM THE MIDDLE 50S
WEST OF THE ILLINOIS RIVER...TO THE LOWER 60S SOUTH OF I-70.
BARNES
&&
.AVIATION...
ISSUED 525 AM CST SAT NOV 21 2009
MAIN FORECAST CONCERN WL BE WITH THE POTENTIAL FOR LOCALLY DENSE
FOG THRU 14Z THIS MORNING. FOG DEVELOPMENT THIS MORNING HAS BEEN
QUITE A BIT SLOWER THAN LAST NIGHT AT THIS TIME. ONE NEGATIVE
FACTOR FOR THE FORMATION OF WIDESPREAD FOG HAS BEEN WITH SOME
SCT-BKN STRATOCU THAT HAS BEEN PUSHING EWD ACRS PARTS OF THE
AREA EARLY THIS MRNG. WL STILL INCLUDE A TEMPO GROUP THRU ABT
15Z FOR THE THREAT OF VSBYS DROPPING TO IFR/LIFR CONDITIONS
FOR A BRIEF TIME. FOG SHOULD LIFT BY 15Z WITH FORECAST SOUNDINGS
INDICATING A MOIST LAYER BETWEEN 900-800 MB (3500-4500 FEET) INTO
THIS AFTN SUGGESTING A SCATTERED TO BROKEN DECK...ESP ACRS THE
WESTERN TAF SITES (PIA AND SPI). SFC WINDS WILL BE LIGHT EAST
TO SOUTHEAST INTO TNT WITH SPEEDS AOB 10 KTS.
SMITH
&&
.PREV DISCUSSION...
ISSUED 205 AM CST SAT NOV 21 2009
LATEST SURFACE MAP SHOWING THE CWA UNDERNEATH AN EAST-WEST HIGH
PRESSURE RIDGE...CENTERED IN SOUTHEAST OHIO. SATELLITE FOG
IMAGERY SHOWING PATCHES OF STRATOCUMULUS CLOUDS ACROSS THE EAST
CENTRAL CWA AROUND CHAMPAIGN AND DANVILLE...AS WELL AS SCATTERED
NEAR THE ST LOUIS AREA. DENSE FOG HAS MAINLY BEEN PATCHY THUS
FAR...WITH AVERAGE VISIBILITIES OVER THE CWA IN THE 3 TO 7 MILE
RANGE.
MAIN SHORT TERM CONCERN INVOLVES THE FOG THIS MORNING. IN THE
LONGER RANGE...EVOLUTION OF THE NEXT STORM SYSTEM IN THE TUESDAY-
WEDNESDAY TIME FRAME IS THE PRIMARY FORECAST CONCERN.
SHORT TERM...TODAY THROUGH MONDAY...
THE FOG HAS BEEN SLOWER TO EVOLVE THAN LAST NIGHT...BUT LATEST
SURFACE PLOT SHOWING FOG BECOMING MORE WIDESPREAD ACROSS IOWA AND
ADJACENT AREAS OF MISSOURI AND ILLINOIS. RUC MODEL SUPPORTS SOME
EXPANSION OF THIS AREA...AND WILL KEEP THE DENSE FOG ADVISORY
GOING ACROSS THE NORTHERN CWA. ACROSS THE SOUTH...BELIEVE THE FOG
WILL BE MORE PATCHY IN NATURE...DUE TO THE DRYING THAT TOOK PLACE
IN THE SUNSHINE ON FRIDAY.
OTHER THAN THAT...MODELS IN DECENT AGREEMENT THROUGH MONDAY...
KEEPING THINGS DRY. TEMPERATURES EXPECTED TO REMAIN SEVERAL
DEGREES ABOVE NORMAL. MET/MAV MOS GUIDANCE FAIRLY CLOSE AND DID
NOT SIGNIFICANTLY DEVIATE FROM IT.
LONG TERM...TUESDAY THROUGH FRIDAY...
MAIN FORECAST CHALLENGE INVOLVES EVOLUTION OF UPPER TROUGH THAT
WILL MOVE INTO THE PACIFIC NORTHWEST ON SUNDAY. THE MAJOR MODELS
ALL HAVE A CLOSED CIRCULATION DEVELOPING OVER THE CENTRAL PLAINS
BY TUESDAY MORNING...BUT THE SPEED AND TRACK OF THE SURFACE
FEATURES REMAIN IN QUESTION. GFS HAS SLOWED A BIT BUT CONTINUES TO
BE THE FASTER OF THE EXTENDED MODELS...BRINGING THE COLD FRONT
THROUGH THE CWA BY ABOUT MIDDAY TUESDAY AND HAVING WRAPAROUND
PRECIP AFFECTING THE AREA TUESDAY NIGHT. MEANWHILE...THE ECMWF
PLACES THE SURFACE LOW IN SOUTHEAST NEBRASKA AT 12Z TUESDAY AND
MOVES IT TO NEAR ROCKFORD BY 12Z WEDNESDAY...WITH THE SURFACE
FRONT PASSING THROUGH OUR AREA SHORTLY AFTERWARD. TRENDED TOWARD
THE SLOWER SOLUTION AND THUS REDUCED POPS TO SLIGHT CHANCE ACROSS
THE EASTERN CWA MONDAY NIGHT. WENT AHEAD AND ADDED SOME LOW CHANCE
POPS TUESDAY NIGHT AND WEDNESDAY ACROSS THE NORTH...AS THAT AREA
SHOULD AT LEAST BE GETTING SOME WRAPAROUND PRECIPITATION FROM THE
GFS SOLUTION...OR FROM THE FRONT ITSELF IN THE ECMWF SOLUTION.
SOUTHERN CWA IS NOT AS CLEAR CUT AT THIS TIME...AND WILL NOT
CHANGE THE POPS IN THAT AREA. UNTIL MORE CONSISTENCY DEVELOPS.
1000-500MB THICKNESS...AS WELL AS BUFKIT SOUNDINGS...WOULD SUGGEST
THAT PRECIP TYPE WOULD BE A CONCERN AS WELL. CURRENTLY PLAN TO
LIMIT ANY MIXED PRECIP TO THE FAR NORTHERN CWA FOR TUESDAY NIGHT.
BOTH MODELS SHOWING WEAK TROUGHS MOVING THROUGH ON THANKSGIVING
DAY...FOLLOWED BY HIGH PRESSURE RIDGING BUILDING IN FROM THE WEST.
HOWEVER...NO CHANGES WERE MADE TO THIS PORTION OF THE FORECAST.
GEELHART
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
000
FXUS63 KLOT 211215
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
615 AM CST SAT NOV 21 2009
.DISCUSSION...
306 AM CST
SHORT TERM CONCERNS CENTER ON FOG POTENTIAL EARLY THIS MORNING AND
AGAIN TONIGHT. ATTENTION THEN TURNS TO MID WEEK STORM SYSTEM.
THIS MORNING...REGION REMAINS SITUATED UNDER THE CONTROL OF
SURFACE RIDGE EXTENDING FROM MID ATLANTIC STATES WEST THROUGH
CENTRAL ILLINOIS. SKIES HAVE BEEN ABLE TO CLEAR OUT ACROSS MUCH
OF THE REGION IN THE WAKE OF DEPARTING WEAK SHORTWAVE. AS A
RESULT...FOG HAS FORMED ACROSS MUCH OF THE AREA...WITH MANY
LOCATIONS SO FAR DIPPING INTO THE 2-4 SM RANGE THIS MORNING.
WOULDN`T BE SURPRISED TO SEE VIS LOWER A LITTLE MORE TOWARD
SUNRISE AS PBL CONTINUES TO COOL...AND PATCHES OF DENSE FOG WILL
REMAIN POSSIBLE THROUGH MID MORNING.
ONCE THE FOG DISSIPATES LATER TODAY...SHOULD SEE THE BEGINNINGS OF
A VERY NICE MID NOVEMBER WEEKEND WITH AFTERNOON HIGHS WARMING INTO
THE MID 50S ACROSS THE AREA. SCENARIO BASICALLY REPEATS ITSELF
TONIGHT AND SUNDAY...WITH PATCHY FOG AGAIN POSSIBLE LATE TONIGHT
AND SUNDAY MORNING...AND HIGHS ON SUNDAY IN THE MID TO PERHAPS
UPPER 60S.
ON MONDAY...ADVERTISED MID WEEK STORM SYSTEM WILL BE BEGINNING TO
ORGANIZE OVER THE NORTHERN HIGH PLAINS. EXPECT TO SEE MID AND HIGH
LEVEL CLOUD COVER START TO INCREASE AS WAA TAKES SHAPE ACROSS
AREAS JUST TO THE WEST OF LOT CWA. NUMERICAL GUIDANCE CONTINUES TO
STRUGGLE WITH EVOLUTION OF THIS SYSTEM...WITH ECMWF GENERALLY
SLOWER AND MORE CUTOFF FROM MAIN WESTERLIES COMPARED TO MUCH MORE
PROGRESSIVE OPERATIONAL GFS. CANADIAN AND GFS ENSEMBLES HAVE
GENERALLY BEEN SPLITTING THE DIFFERENCE...AND SEEM LIKE THE
PRUDENT SOLUTION TO FOLLOW UNTIL DETAILS BECOME LESS MUDDY. OF
NOTE...00Z EURO THAT CAME IN EARLY THIS MORNING HAS COME IN MORE
PROGRESSIVE...SEEMINGLY AT LEAST A TREND TOWARD GENERAL IDEA OF
GFS ENSEMBLE/CANADIAN.
CONFIDENCE IS STARTING TO INCREASE THAT RAIN WILL OVERSPREAD THE
AREA TUESDAY INTO WEDNESDAY AS OCCLUDING FRONT MOVES THROUGH THE
AREA. CHANCES ARE THAT DRY SLOT OF SOME SORT WILL MOVE IN BEHIND
THIS FIRST SHOT OF RAIN...BUT ATTEMPTING TO DETERMINE SPECIFICS OF
SUCH A DETAIL AT THIS DISTANCE ALL BUT IMPOSSIBLE. ADDITIONAL
PRECIPITATION WILL BE POSSIBLE WEDNESDAY AND THURSDAY AS MAIN
UPPER TROUGH AXIS...AND PERHAPS SECONDARY COLD FRONT...PUSHES
THROUGH. PRECIP TYPE CERTAINLY IN QUESTION WEDNESDAY NIGHT ONWARD
AS GFS IS TRENDING COLDER THAN EURO. SPECIFICS OF RAIN VS SNOW
WILL BE ENTIRELY DEPENDENT ON EXACT TRACK AND STRENGTH OF UPPER
TROUGH. AT THIS TIME...DECIDED TO CHANGE LITTLE IN THE WAY OF
INHERITED PRECIP TYPE TO AVOID POTENTIAL FLIP FLOPS IN LATER
FORECASTS.
BOXELL
&&
.AVIATION...
613 AM CST
1200 UTC TAFS...AVIATION FORECAST CONCERNS WILL BE FOG BOTH EARLY
THIS MORNING AND SUNDAY MORNING.
SURFACE RIDGE AXIS EXTENDS FROM THE WEST VIRGINIA INTO NORTHERN
ILLINOIS EARLY THIS MORNING. SUBSIDENCE IN THE WAKE OF DEPARTING
UPPER LEVEL SHORT WAVE ACROSS WESTERN GREAT LAKES HAS ALLOWED FOR
MAINLY CLEAR SKIES ACROSS FAR NORTHERN ILLINOIS...ALTHOUGH SOME
PATCHY STRATOCU NOTED ON SATELLITE IMAGERY THIS MORNING ACROSS
CENTRAL ILLINOIS AND ACROSS EASTERN IOWA. BASED ON CURRENT
SATELLITE TRENDS AND EXPECTATION OF CONTINUED SYNOPTIC SCALE
SUBSIDENCE...NOT EXPECTING THESE LOW CLOUDS TO AFFECT TERMINALS.
CLEAR SKIES/LIGHT WINDS HAVE LED TO CONDUCIVE RADIATIONAL COOLING
CONDITIONS AND PATCHY FOG IS COMMON ACROSS THE AREA. ORD/MDW
GENERALLY HOLDING AT OR ABOVE 5 MILES FOR VSBYS WITH TEMPORARY
VSBY REDUCTIONS TO IFR AT DPA. DID INCLUDE TEMPO IFR VSBYS FOR
PATCHY DENSER SHALLOW FOG FOR A FEW HOURS THIS MORNING THROUGH 14Z
AT DPA/RFD CLOSER TO THE SFC RIDGE AXIS. AFTER MORNING FOG
DISSIPATES...QUIET WEATHER EXPECTED THROUGH THE DAY WITH PERHAPS
SOME LOW COVERAGE CU DEVELOPING AROUND 3K FT...BUT NOT EXPECTING
CIGS AT THIS TIME. SURFACE RIDGE AXIS BEGINNING TO DEPART TO THE
EAST SHOULD RESULT IN LIGHT SOUTHEAST WINDS THROUGH THE DAY OF 5
TO 10 KNOTS. GOOD RADIATIONAL COOLING CONDITIONS IN STORE AGAIN
TONIGHT WITH WINDS EXPECTED TO BECOME LIGHT ONCE AGAIN UNDER MOSTLY
CLEAR SKIES. AT THIS TIME HAVE INCLUDED MVFR VSBYS ACROSS ALL
TERMINALS TONIGHT...BUT LATER FORECASTS MAY NEED TO GO A BIT MORE
PESSIMISTIC AT DPA/RFD WITH POSSIBILITY OF SOME SHORT LIVED IFR
VSBYS NOT OUT OF THE QUESTION...BUT DID NOT HAVE CONFIDENCE TO
INSERT WITH THE 12Z TAFS AT THIS FORECAST DISTANCE.
MARSILI
&&
.MARINE...
306 AM CST
OVERALL VERY FEW CHANGES MADE TO THE NEARSHORE AND OPEN WATERS
FORECAST. A BROAD SURFACE ANTICYCLONE STRETCHING FROM NORTHERN
ILLINOIS TO WEST VIRGINIA WILL CONTINUE TO SLOWLY SLIDE EAST OF THE
AREA SETTING UP A LIGHT SOUTH WIND OVER LAKE MICHIGAN FOR THIS
AFTERNOON. UPPER LEVEL RIDGING IS EXPECTED TO PERSIST ACROSS
SOUTHEAST CANADA/NORTHEAST UNITED STATES OVER NEXT FEW DAYS WHICH
WILL ALLOW SOME WEAK SURFACE RIDGING TO HANG BACK ACROSS THE GREAT
LAKES REGION. THUS...DESPITE MAIN SURFACE ANTICYCLONE SHIFTING EAST
NORTHEAST NEXT FEW DAYS...GRADIENT WILL BE SLOW TO STRENGTHEN...SO
MODEST SOUTH WIND SPEED INCREASES INTO THE 10 TO 15 KT RANGE STILL
SEEMS REASONABLE BY SUNDAY. A FAIRLY STRONG UPPER LEVEL TROUGH WILL
MOVE INTO THE CENTRAL PLAINS MONDAY NIGHT/TUESDAY WITH NEXT SFC LOW
TAKING SHAPE ACROSS THE CENTRAL PLAINS. THIS LOW WILL APPROACH THE
WESTERN GREAT LAKES BY WEDNESDAY. THE EXPECTED TRACK OF THIS LOW
WOULD SUPPORT CONTINUED SOUTH SOUTHEAST WINDS THROUGH MIDDLE OF NEXT
WEEK. WHILE SPEEDS ARE EXPECTED TO GENERALLY REMAIN IN THE 10 TO 20
KNOT RANGE...THE EXTENDED SOUTH SOUTHEAST FETCH COULD ALLOW WAVE
HEIGHTS TO BUILD INTO THE 3 TO 5 FT RANGE TOWARD THE END OF THE
FORECAST PERIOD LATE TUESDAY NIGHT INTO WEDNESDAY.
MARSILI
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...DENSE FOG ADVISORY...ILZ008-ILZ010-ILZ019-ILZ021-ILZ023-ILZ032-
ILZ039 UNTIL 9 AM SATURDAY.
IN...NONE.
LM...NONE.
&&
$$
000
FXUS63 KILX 211126
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
526 AM CST SAT NOV 21 2009
.DISCUSSION...
ISSUED 205 AM CST SAT NOV 21 2009
LATEST SURFACE MAP SHOWING THE CWA UNDERNEATH AN EAST-WEST HIGH
PRESSURE RIDGE...CENTERED IN SOUTHEAST OHIO. SATELLITE FOG
IMAGERY SHOWING PATCHES OF STRATOCUMULUS CLOUDS ACROSS THE EAST
CENTRAL CWA AROUND CHAMPAIGN AND DANVILLE...AS WELL AS SCATTERED
NEAR THE ST LOUIS AREA. DENSE FOG HAS MAINLY BEEN PATCHY THUS
FAR...WITH AVERAGE VISIBILITIES OVER THE CWA IN THE 3 TO 7 MILE
RANGE.
MAIN SHORT TERM CONCERN INVOLVES THE FOG THIS MORNING. IN THE
LONGER RANGE...EVOLUTION OF THE NEXT STORM SYSTEM IN THE TUESDAY-
WEDNESDAY TIME FRAME IS THE PRIMARY FORECAST CONCERN.
SHORT TERM...TODAY THROUGH MONDAY...
THE FOG HAS BEEN SLOWER TO EVOLVE THAN LAST NIGHT...BUT LATEST
SURFACE PLOT SHOWING FOG BECOMING MORE WIDESPREAD ACROSS IOWA AND
ADJACENT AREAS OF MISSOURI AND ILLINOIS. RUC MODEL SUPPORTS SOME
EXPANSION OF THIS AREA...AND WILL KEEP THE DENSE FOG ADVISORY
GOING ACROSS THE NORTHERN CWA. ACROSS THE SOUTH...BELIEVE THE FOG
WILL BE MORE PATCHY IN NATURE...DUE TO THE DRYING THAT TOOK PLACE
IN THE SUNSHINE ON FRIDAY.
OTHER THAN THAT...MODELS IN DECENT AGREEMENT THROUGH MONDAY...
KEEPING THINGS DRY. TEMPERATURES EXPECTED TO REMAIN SEVERAL
DEGREES ABOVE NORMAL. MET/MAV MOS GUIDANCE FAIRLY CLOSE AND DID
NOT SIGNIFICANTLY DEVIATE FROM IT.
LONG TERM...TUESDAY THROUGH FRIDAY...
MAIN FORECAST CHALLENGE INVOLVES EVOLUTION OF UPPER TROUGH THAT
WILL MOVE INTO THE PACIFIC NORTHWEST ON SUNDAY. THE MAJOR MODELS
ALL HAVE A CLOSED CIRCULATION DEVELOPING OVER THE CENTRAL PLAINS
BY TUESDAY MORNING...BUT THE SPEED AND TRACK OF THE SURFACE
FEATURES REMAIN IN QUESTION. GFS HAS SLOWED A BIT BUT CONTINUES TO
BE THE FASTER OF THE EXTENDED MODELS...BRINGING THE COLD FRONT
THROUGH THE CWA BY ABOUT MIDDAY TUESDAY AND HAVING WRAPAROUND
PRECIP AFFECTING THE AREA TUESDAY NIGHT. MEANWHILE...THE ECMWF
PLACES THE SURFACE LOW IN SOUTHEAST NEBRASKA AT 12Z TUESDAY AND
MOVES IT TO NEAR ROCKFORD BY 12Z WEDNESDAY...WITH THE SURFACE
FRONT PASSING THROUGH OUR AREA SHORTLY AFTERWARD. TRENDED TOWARD
THE SLOWER SOLUTION AND THUS REDUCED POPS TO SLIGHT CHANCE ACROSS
THE EASTERN CWA MONDAY NIGHT. WENT AHEAD AND ADDED SOME LOW CHANCE
POPS TUESDAY NIGHT AND WEDNESDAY ACROSS THE NORTH...AS THAT AREA
SHOULD AT LEAST BE GETTING SOME WRAPAROUND PRECIPITATION FROM THE
GFS SOLUTION...OR FROM THE FRONT ITSELF IN THE ECMWF SOLUTION.
SOUTHERN CWA IS NOT AS CLEAR CUT AT THIS TIME...AND WILL NOT
CHANGE THE POPS IN THAT AREA. UNTIL MORE CONSISTENCY DEVELOPS.
1000-500MB THICKNESS...AS WELL AS BUFKIT SOUNDINGS...WOULD SUGGEST
THAT PRECIP TYPE WOULD BE A CONCERN AS WELL. CURRENTLY PLAN TO
LIMIT ANY MIXED PRECIP TO THE FAR NORTHERN CWA FOR TUESDAY NIGHT.
BOTH MODELS SHOWING WEAK TROUGHS MOVING THROUGH ON THANKSGIVING
DAY...FOLLOWED BY HIGH PRESSURE RIDGING BUILDING IN FROM THE WEST.
HOWEVER...NO CHANGES WERE MADE TO THIS PORTION OF THE FORECAST.
GEELHART
&&
.AVIATION...
ISSUED 525 AM CST SAT NOV 21 2009
MAIN FORECAST CONCERN WL BE WITH THE POTENTIAL FOR LOCALLY DENSE
FOG THRU 14Z THIS MORNING. FOG DEVELOPMENT THIS MORNING HAS BEEN
QUITE A BIT SLOWER THAN LAST NIGHT AT THIS TIME. ONE NEGATIVE
FACTOR FOR THE FORMATION OF WIDESPREAD FOG HAS BEEN WITH SOME
SCT-BKN STRATOCU THAT HAS BEEN PUSHING EWD ACRS PARTS OF THE
AREA EARLY THIS MRNG. WL STILL INCLUDE A TEMPO GROUP THRU ABT
15Z FOR THE THREAT OF VSBYS DROPPING TO IFR/LIFR CONDITIONS
FOR A BRIEF TIME. FOG SHOULD LIFT BY 15Z WITH FORECAST SOUNDINGS
INDICATING A MOIST LAYER BETWEEN 900-800 MB (3500-4500 FEET) INTO
THIS AFTN SUGGESTING A SCATTERED TO BROKEN DECK...ESP ACRS THE
WESTERN TAF SITES (PIA AND SPI). SFC WINDS WILL BE LIGHT EAST
TO SOUTHEAST INTO TNT WITH SPEEDS AOB 10 KTS.
SMITH
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
DENSE FOG ADVISORY UNTIL 9 AM CST THIS MORNING FOR ILZ027>031-
036>038-040-041.
&&
$$
000
FXUS63 KLOT 210906
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
306 AM CST SAT NOV 21 2009
.DISCUSSION...
306 AM CST
SHORT TERM CONCERNS CENTER ON FOG POTENTIAL EARLY THIS MORNING AND
AGAIN TONIGHT. ATTENTION THEN TURNS TO MID WEEK STORM SYSTEM.
THIS MORNING...REGION REMAINS SITUATED UNDER THE CONTROL OF
SURFACE RIDGE EXTENDING FROM MID ATLANTIC STATES WEST THROUGH
CENTRAL ILLINOIS. SKIES HAVE BEEN ABLE TO CLEAR OUT ACROSS MUCH
OF THE REGION IN THE WAKE OF DEPARTING WEAK SHORTWAVE. AS A
RESULT...FOG HAS FORMED ACROSS MUCH OF THE AREA...WITH MANY
LOCATIONS SO FAR DIPPING INTO THE 2-4 SM RANGE THIS MORNING.
WOULDN`T BE SURPRISED TO SEE VIS LOWER A LITTLE MORE TOWARD
SUNRISE AS PBL CONTINUES TO COOL...AND PATCHES OF DENSE FOG WILL
REMAIN POSSIBLE THROUGH MID MORNING.
ONCE THE FOG DISSIPATES LATER TODAY...SHOULD SEE THE BEGINNINGS OF
A VERY NICE MID NOVEMBER WEEKEND WITH AFTERNOON HIGHS WARMING INTO
THE MID 50S ACROSS THE AREA. SCENARIO BASICALLY REPEATS ITSELF
TONIGHT AND SUNDAY...WITH PATCHY FOG AGAIN POSSIBLE LATE TONIGHT
AND SUNDAY MORNING...AND HIGHS ON SUNDAY IN THE MID TO PERHAPS
UPPER 60S.
ON MONDAY...ADVERTISED MID WEEK STORM SYSTEM WILL BE BEGINNING TO
ORGANIZE OVER THE NORTHERN HIGH PLAINS. EXPECT TO SEE MID AND HIGH
LEVEL CLOUD COVER START TO INCREASE AS WAA TAKES SHAPE ACROSS
AREAS JUST TO THE WEST OF LOT CWA. NUMERICAL GUIDANCE CONTINUES TO
STRUGGLE WITH EVOLUTION OF THIS SYSTEM...WITH ECMWF GENERALLY
SLOWER AND MORE CUTOFF FROM MAIN WESTERLIES COMPARED TO MUCH MORE
PROGRESSIVE OPERATIONAL GFS. CANADIAN AND GFS ENSEMBLES HAVE
GENERALLY BEEN SPLITTING THE DIFFERENCE...AND SEEM LIKE THE
PRUDENT SOLUTION TO FOLLOW UNTIL DETAILS BECOME LESS MUDDY. OF
NOTE...00Z EURO THAT CAME IN EARLY THIS MORNING HAS COME IN MORE
PROGRESSIVE...SEEMINGLY AT LEAST A TREND TOWARD GENERAL IDEA OF
GFS ENSEMBLE/CANADIAN.
CONFIDENCE IS STARTING TO INCREASE THAT RAIN WILL OVERSPREAD THE
AREA TUESDAY INTO WEDNESDAY AS OCCLUDING FRONT MOVES THROUGH THE
AREA. CHANCES ARE THAT DRY SLOT OF SOME SORT WILL MOVE IN BEHIND
THIS FIRST SHOT OF RAIN...BUT ATTEMPTING TO DETERMINE SPECIFICS OF
SUCH A DETAIL AT THIS DISTANCE ALL BUT IMPOSSIBLE. ADDITIONAL
PRECIPITATION WILL BE POSSIBLE WEDNESDAY AND THURSDAY AS MAIN
UPPER TROUGH AXIS...AND PERHAPS SECONDARY COLD FRONT...PUSHES
THROUGH. PRECIP TYPE CERTAINLY IN QUESTION WEDNESDAY NIGHT ONWARD
AS GFS IS TRENDING COLDER THAN EURO. SPECIFICS OF RAIN VS SNOW
WILL BE ENTIRELY DEPENDENT ON EXACT TRACK AND STRENGTH OF UPPER
TROUGH. AT THIS TIME...DECIDED TO CHANGE LITTLE IN THE WAY OF
INHERITED PRECIP TYPE TO AVOID POTENTIAL FLIP FLOPS IN LATER
FORECASTS.
BOXELL
&&
.AVIATION...
0600 UTC TAFS...MAIN CONCERN FOR THE REMAINDER OF THE NIGHT
CONTINUES TO FOCUS ON VISIBILITY...PARTICULARLY AT RFD/DPA AND
DURING THE EARLY MORNING HOURS.
THE LATEST SATELLITE IMAGERY SHOWS QUICKLY CLEARING. THIS WILL
ENHANCE RADIATIVE COOLING...AND WHEN COMBINED WITH SATURATED
GROUND AND WINDS QUICKLY BECOME LGT/VRBL...VISIBILITY SHOULD DROP
TO MVFR AT RFD/DPA SHORTLY AFTER MIDNIGHT. DUE TO URBAN
INFLUENCES...ORD/MDW SHOULD BE A LITTLE SLOWER TO RESPOND AND NOT
DROP TO MVFR UNTIL A FEW HOURS LATER. ORD/MDW SHOULD REMAIN AT
MVFR WITH RFD/DPA HAVING A BETTER CHANCE TO DROP TO
IFR...ESPECIALLY DURG THE PRE-DAWN HOURS.
THE FOG SHOULD BURN OFF SHORTLY AFTER SUNRISE AND THE REMAINDER OF
THE DAY WILL BE QUIET FOR AVIATION WEATHER CONCERNS.
KREIN
&&
.MARINE...
306 AM CST
OVERALL VERY FEW CHANGES MADE TO THE NEARSHORE AND OPEN WATERS
FORECAST. A BROAD SURFACE ANTICYCLONE STRETCHING FROM NORTHERN
ILLINOIS TO WEST VIRGINIA WILL CONTINUE TO SLOWLY SLIDE EAST OF THE
AREA SETTING UP A LIGHT SOUTH WIND OVER LAKE MICHIGAN FOR THIS
AFTERNOON. UPPER LEVEL RIDGING IS EXPECTED TO PERSIST ACROSS
SOUTHEAST CANADA/NORTHEAST UNITED STATES OVER NEXT FEW DAYS WHICH
WILL ALLOW SOME WEAK SURFACE RIDGING TO HANG BACK ACROSS THE GREAT
LAKES REGION. THUS...DESPITE MAIN SURFACE ANTICYCLONE SHIFTING EAST
NORTHEAST NEXT FEW DAYS...GRADIENT WILL BE SLOW TO STRENGTHEN...SO
MODEST SOUTH WIND SPEED INCREASES INTO THE 10 TO 15 KT RANGE STILL
SEEMS REASONABLE BY SUNDAY. A FAIRLY STRONG UPPER LEVEL TROUGH WILL
MOVE INTO THE CENTRAL PLAINS MONDAY NIGHT/TUESDAY WITH NEXT SFC LOW
TAKING SHAPE ACROSS THE CENTRAL PLAINS. THIS LOW WILL APPROACH THE
WESTERN GREAT LAKES BY WEDNESDAY. THE EXPECTED TRACK OF THIS LOW
WOULD SUPPORT CONTINUED SOUTH SOUTHEAST WINDS THROUGH MIDDLE OF NEXT
WEEK. WHILE SPEEDS ARE EXPECTED TO GENERALLY REMAIN IN THE 10 TO 20
KNOT RANGE...THE EXTENDED SOUTH SOUTHEAST FETCH COULD ALLOW WAVE
HEIGHTS TO BUILD INTO THE 3 TO 5 FT RANGE TOWARD THE END OF THE
FORECAST PERIOD LATE TUESDAY NIGHT INTO WEDNESDAY.
MARSILI
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...DENSE FOG ADVISORY...ILZ008-ILZ010-ILZ019-ILZ032-ILZ039 UNTIL 9
AM SATURDAY.
IN...NONE.
LM...NONE.
&&
$$
000
FXUS63 KILX 210807
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
207 AM CST SAT NOV 21 2009
.DISCUSSION...
ISSUED 205 AM CST SAT NOV 21 2009
LATEST SURFACE MAP SHOWING THE CWA UNDERNEATH AN EAST-WEST HIGH
PRESSURE RIDGE...CENTERED IN SOUTHEAST OHIO. SATELLITE FOG
IMAGERY SHOWING PATCHES OF STRATOCUMULUS CLOUDS ACROSS THE EAST
CENTRAL CWA AROUND CHAMPAIGN AND DANVILLE...AS WELL AS SCATTERED
NEAR THE ST LOUIS AREA. DENSE FOG HAS MAINLY BEEN PATCHY THUS
FAR...WITH AVERAGE VISIBILITIES OVER THE CWA IN THE 3 TO 7 MILE
RANGE.
MAIN SHORT TERM CONCERN INVOLVES THE FOG THIS MORNING. IN THE
LONGER RANGE...EVOLUTION OF THE NEXT STORM SYSTEM IN THE TUESDAY-
WEDNESDAY TIME FRAME IS THE PRIMARY FORECAST CONCERN.
SHORT TERM...TODAY THROUGH MONDAY...
THE FOG HAS BEEN SLOWER TO EVOLVE THAN LAST NIGHT...BUT LATEST
SURFACE PLOT SHOWING FOG BECOMING MORE WIDESPREAD ACROSS IOWA AND
ADJACENT AREAS OF MISSOURI AND ILLINOIS. RUC MODEL SUPPORTS SOME
EXPANSION OF THIS AREA...AND WILL KEEP THE DENSE FOG ADVISORY
GOING ACROSS THE NORTHERN CWA. ACROSS THE SOUTH...BELIEVE THE FOG
WILL BE MORE PATCHY IN NATURE...DUE TO THE DRYING THAT TOOK PLACE
IN THE SUNSHINE ON FRIDAY.
OTHER THAN THAT...MODELS IN DECENT AGREEMENT THROUGH MONDAY...
KEEPING THINGS DRY. TEMPERATURES EXPECTED TO REMAIN SEVERAL
DEGREES ABOVE NORMAL. MET/MAV MOS GUIDANCE FAIRLY CLOSE AND DID
NOT SIGNIFICANTLY DEVIATE FROM IT.
LONG TERM...TUESDAY THROUGH FRIDAY...
MAIN FORECAST CHALLENGE INVOLVES EVOLUTION OF UPPER TROUGH THAT
WILL MOVE INTO THE PACIFIC NORTHWEST ON SUNDAY. THE MAJOR MODELS
ALL HAVE A CLOSED CIRCULATION DEVELOPING OVER THE CENTRAL PLAINS
BY TUESDAY MORNING...BUT THE SPEED AND TRACK OF THE SURFACE
FEATURES REMAIN IN QUESTION. GFS HAS SLOWED A BIT BUT CONTINUES TO
BE THE FASTER OF THE EXTENDED MODELS...BRINGING THE COLD FRONT
THROUGH THE CWA BY ABOUT MIDDAY TUESDAY AND HAVING WRAPAROUND
PRECIP AFFECTING THE AREA TUESDAY NIGHT. MEANWHILE...THE ECMWF
PLACES THE SURFACE LOW IN SOUTHEAST NEBRASKA AT 12Z TUESDAY AND
MOVES IT TO NEAR ROCKFORD BY 12Z WEDNESDAY...WITH THE SURFACE
FRONT PASSING THROUGH OUR AREA SHORTLY AFTERWARD. TRENDED TOWARD
THE SLOWER SOLUTION AND THUS REDUCED POPS TO SLIGHT CHANCE ACROSS
THE EASTERN CWA MONDAY NIGHT. WENT AHEAD AND ADDED SOME LOW CHANCE
POPS TUESDAY NIGHT AND WEDNESDAY ACROSS THE NORTH...AS THAT AREA
SHOULD AT LEAST BE GETTING SOME WRAPAROUND PRECIPITATION FROM THE
GFS SOLUTION...OR FROM THE FRONT ITSELF IN THE ECMWF SOLUTION.
SOUTHERN CWA IS NOT AS CLEAR CUT AT THIS TIME...AND WILL NOT
CHANGE THE POPS IN THAT AREA. UNTIL MORE CONSISTENCY DEVELOPS.
1000-500MB THICKNESS...AS WELL AS BUFKIT SOUNDINGS...WOULD SUGGEST
THAT PRECIP TYPE WOULD BE A CONCERN AS WELL. CURRENTLY PLAN TO
LIMIT ANY MIXED PRECIP TO THE FAR NORTHERN CWA FOR TUESDAY NIGHT.
BOTH MODELS SHOWING WEAK TROUGHS MOVING THROUGH ON THANKSGIVING
DAY...FOLLOWED BY HIGH PRESSURE RIDGING BUILDING IN FROM THE WEST.
HOWEVER...NO CHANGES WERE MADE TO THIS PORTION OF THE FORECAST.
GEELHART
&&
.AVIATION...
ISSUED 1116 PM CST FRI NOV 20 2009
LIGHT FOG HAS DEVELOPED AT SOME SITES TONIGHT WHILE OTHERS ARE
SLOW. HOWEVER...DENSE FOG...VLIFR VIS CAN BE EXPECTED BY MORNING
AT BMI AND PIA WHILE SPI...DEC AND CMI WILL SEE VIS DOWN TO AROUND
A MILE BY MORNING. CLOUD COVER OVER CMI HAS FINALLY MOVED
NORTHEAST AND EXPECT MOSTLY CLEAR SKIES AT ALL TAF SITES
OVERNIGHT. BY MID MORNING...MODEL BRING SOME HIGHER RH VALUES INTO
THE WESTERN HALF OF THE REGION AND AM EXPECTING BKN CIGS AT AROUND
4KFT TO ADVECT INTO SPI...DEC AND THEN AT BMI AND PIA LATER THIS
MORNING AND INTO THIS AFTERNOON. CLOUD COVER SHOULD BECOME
SCATTERED IN THE LATE AFTERNOON TO EARLY EVENING HOURS AS THE
CLOUDS MOVE NORTH THROUGH THE AREA. CMI SHOULD REMAIN SCATTERED
ALL DAY AS THE HIGHEST RH VALUES REMAIN WEST OF THE TAF SITE.
LIGHT WINDS WILL BECOME SOUTHEAST TOMORROW AND REMAIN LESS THAN 10MPH.
AUTEN
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
DENSE FOG ADVISORY UNTIL 9 AM CST THIS MORNING FOR ILZ027>031-
036>038-040-041.
&&
$$
| 
