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000
FXUS64 KJAN 212130
AFDJAN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON MS
330 PM CST SAT NOV 21 2009
.SHORT TERM...TONIGHT THROUGH MONDAY NIGHT...IT HAS BEEN A WET SATURDAY
FOR SOME FOLKS ACROSS THE ARKLAMISS. SURFACE LOW PRESSURE SYSTEM
ALONG THE GULF COAST IS SLOWLY MOVING EAST...WITH UPPER LOW/SHORTWAVE
TROUGH ACROSS EASTERN OKLAHOMA. THESE FEATURES ARE CREATING ENOUGH
LIFT FOR A SHIELD OF SHOWERS AND ONE OR TWO THUNDERSTORMS ACROSS
SOUTHERN LOUISIANA. THIS ACTIVITY HAS SLOWLY BEEN MOVING NORTH THIS
AFTERNOON AND AFFECTING LOCATIONS ALONG AND SOUTH OF THE INTERSTATE
20 CORRIDOR. MUCH OF THIS IS LIGHT RAIN WITH SOME AREAS OF MODERATE
RAIN.
FOR TONIGHT...AS THE LOW ACROSS THE GULF CONTINUES TO MOVE FROM WEST
TO EAST...THIS RAIN SHOULD CONTINUE TO SPREAD OVER THE AREA WITH THE
SREF/GFS/LOCAL WRF ALL SHOWING THE BETTER COVERAGE OF RAIN REMAINING
ACROSS CENTRAL AND SOUTHERN SECTIONS AT LEAST FOR THE FIRST HALF OF
THE NIGHT. FOR LATTER PORTIONS...THE LOW WILL CONTINUE ITS TRACK OFF
TO THE NORTHEAST AND THE UPPER TROUGH MOVES OVER THE REGION... THIS
WILL ALLOW THE RAIN CHANCES TO BEGIN TO DIMINISH FOR LOCATIONS ACROSS
THE WEST INTO WEST CENTRAL MS AND BRING THE BETTER CHANCES FOR RAIN
TO THE EAST/NORTHEAST.
ON SUNDAY AND SUNDAY NIGHT...THE UPPER TROUGH AND SFC LOW CONTINUE TO
PULL OFF TO THE NORTHEAST AND THERE COULD BE SOME LIGHT RAIN
LINGERING ACROSS THE EAST FOR EARLY SUNDAY. THIS IS INDICATED BY
LOCAL WRF MODELS AS WELL AS SREF PROBS THAT SHOW THE HIGHEST PROBS
IN THE GOLDEN TRIANGLE REGION. HAVE LEFT IN LOW POPS FOR THE
NORTHEAST INTO EARLY SUNDAY EVENING FOR ANY LINGERING LIGHT RAIN BUT
BELIEVE THE BULK OF THIS WILL BE OUT OF THE REGION. SKIES WILL BEGIN
TO CLEAR FROM THE WEST SUNDAY NIGHT. DEPENDING ON HOW MUCH THE SKIES
CLEAR...THERE COULD BE SOME PATCHY FOG GIVEN DRIER AIR ALOFT. HAVE
KEPT MENTION OF THIS IN THE ZONES FOR THE SOUTH.
BY MONDAY...THE REGION GETS INFLUENCED BY WEAK SFC HIGH PRESSURE AND
ZONAL FLOW ALOFT. THIS TRANSLATES TO A DRY DAY WITH SUNNY
CONDITIONS. HOWEVER...DURING THIS TIME AN UPPER TROUGH CONTINUES TO
DEVELOP ACROSS THE PLAINS. THIS WILL SEND A COLD FRONT OUR WAY ON
TUESDAY. BY MONDAY NIGHT...SOUTHERLY FLOW RETURNS AND CLOUDS BEGIN
TO INCREASE ACROSS THE WEST AHEAD OF THE NEXT SYSTEM.
OVERALL...REMAINED CLOSE TO GUI PAST THE FIRST PERIOD AS CONDITIONS
LOOK TO DRY OUT. DID RAISE POPS FOR TONIGHT ACROSS THE EAST AND
PORTIONS OF THE CENTRAL AS MODEL GUI INDICATES THIS WILL BE THE MOST
LIKELY PLACE FOR RAINFALL. /28/
.LONG TERM...TUESDAY THROUGH SATURDAY...A RATHER FLAT ZONAL FLOW PATTERN
WILL TRANSITION BACK TO RIDGING IN THE WRN CONUS AND TROUGHING IN THE
E DURING THE COMING HOLIDAY WEEK. THE PRIMARY FEATURE FOR THE WEEK
APPEARS TO BE A WEAK FRONTAL SYSTEM PASSING THROUGH THE LOWER MS
VALLEY TUESDAY AND TUESDAY NIGHT WITH MINIMAL RAINFALL CHANCES. THIS
BOUNDARY IS FOLLOWED BY TWO REINFORCING TROUGHS WEDNESDAY NIGHT AND
LATER ON SATURDAY TO KEEP US COOLER THAN CLIMATOLOGY.
THE GFS IS NOW MUSTERING UP 0.75-1.0 INCH PWATS ALONG THE
TUESDAY FRONT BEFORE RETURNING TO 0.25 INCHES ON WEDNESDAY. PRE
FRONTAL LOW LEVEL RIDGING ALONG THE GULF COAST SHOULD PREVENT MUCH
MOISTURE RETURN AND DO NOT SEE MUCH MOISTURE CONVERGENCE WITH THE
BOUNDARY SO WILL KEEP MENTION TO LIGHT RAIN. THE ECMWF IS ACTUALLY A
LITTLE WETTER WITH THIS FRONT AS IT SHOWS A TENTH OF AN INCH QPFS
HANGING ON INTO TUESDAY EVENING OVER THE SERN PORTIONS OF OUR CWFA.
BEYOND THAT...A QUICK REINFORCING DRY TROUGH SWEEPS THROUGH THE AREA
WITH A FEW CLOUDS FOR WEDNESDAY NIGHT. THIS SETS UP A CHILLY CAA
CELEBRATION FOR THANKSGIVING DAY WITH MOST LOWS IN THE U30S AND HIGHS
IN THE 50S.
A 1020+MB SURFACE HIGH OVER SERN TX FRIDAY MOVES ALONG THE GULF COAST
FOR FRIDAY NIGHT AND SATURDAY WITH SOME MOISTURE RETURN FOR SATURDAY
NIGHT. ANOTHER WEAK FRONT COULD REACH THE AREA BY THAT TIME BUT IT
ALSO IS APPEARING RATHER DRY WITH THE SURFACE HIGH OFF THE COAST OF
NW FL. WILL HAVE TO MONITOR THIS TIME FRAME AS THE ECMWF AGAIN A
LITTLE MORE ROBUST WITH THE MASS FIELDS AND HIGHER RAIN CHANCES.
ALL IN ALL...THE HOLIDAY WEEK SHOULD BE QUITE DRY AND ALSO SEASONABLE
IN THE TEMPERATURE DEPARTMENT. THE ENSEMBLE MOS GUIDANCE STAYS WITHIN
1-2 STANDARD DEVIATIONS AND IN MOST CASES THE MEANS ARE CLOSE TO THE
OPERATIONAL NUMBERS./40/
&&
.AVIATION...A LOW PRESSURE SYSTEM MOVING ALONG THE GULF COAST IS
BRINGING LOWER CEILINGS AND LIGHT TO MDT RAIN TO MUCH OF THE AREA
THIS AFTERNOON...BUT THE DRY AIR IS KEEPING RESTRICTIONS IN THE VFR
RANGE SO FAR. AS THE RAIN CONTINUES TO MOISTEN THE LOWER LEVELS AND
THE UPPER LOW APPROACHES...LOOK FOR MVFR RESTRICTIONS TO DEVELOP AT
HBG/MEI/JAN DURING THIS EVENING...WITH IFR RESTRICTIONS POSSIBLE AT
HBG/MEI DUE TO HEAVIER RAINFALL. INSTABILITY WILL BE MARGINAL BUT
COULD SUPPORT A LITTLE TSTM ACTIVITY AT HBG/MEI. IT LOOKS LIKE
GLH/GWO/GTR WILL STAY IN VFR CATEGORY FOR MOST OF THE RAIN EVENT
GIVEN THE DRY AIR CURRENTLY IN PLACE. AS THE UPPER LOW BEGINS TO
MOVE ACROSS THE FORECAST AREA LATE TONIGHT AND SUNDAY MORNING...
RAINFALL WILL DIMINISH...BUT STRATUS WILL BECOME WIDESPREAD
RESULTING IN MVFR/IFR RESTRICTIONS AT ALL SITES. THE STRATUS WILL
HANG AROUND THROUGH SUNDAY AFTERNOON AND COULD LINGER SUNDAY
NIGHT...ESPECIALLY OVER CNTRL/ERN MS. /EC/
&&
.PRELIMINARY POINT TEMPS/POPS...
JACKSON 50 59 49 66 / 95 20 9 7
MERIDIAN 50 60 47 66 / 97 39 19 8
VICKSBURG 49 60 46 66 / 81 10 6 6
HATTIESBURG 52 61 48 67 / 97 28 9 7
NATCHEZ 48 59 43 68 / 82 8 6 5
GREENVILLE 48 59 47 65 / 55 20 9 7
GREENWOOD 48 56 48 67 / 87 28 15 8
&&
.JAN WATCHES/WARNINGS/ADVISORIES...
MS...NONE.
LA...NONE.
AR...NONE.
&&
$$
28/40/EC
000
FXUS64 KJAN 211638 AAA
AFDJAN
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE JACKSON MS
1038 AM CST SAT NOV 21 2009
.UPDATE...LOOKS LIKE A CLOUDY...RAINY AND DREARY SATURDAY IN
STORE FOR MUCH OF THE ARKLAMISS. RAIN SHIELD...ASSOCIATED WITH SFC
LOW AND ISENTROPIC LIFT OVER ATTENDANT WARM FRONT...LOCATED ACROSS
MUCH OF SOUTHERN LOUISIANA...MOVING NORTH. THIS IS EXPECTED TO
CONTINUE THROUGH THE DAY. MUCH OF THIS SHOULD BE LIGHT IN NATURE AND
MOSTLY RAIN THOUGH THERE COULD BE AN ISOLATED THUNDERSTORM LOCATED
SOUTH. MODELS CONTINUE TO INDICATE THAT THE BEST CONCENTRATION FOR
RAIN WILL REMAIN IN THE SOUTH...BUT THERE STILL COULD BE SOME LIGHT
RAIN ACROSS NORTHERN PORTIONS. LOCAL WRF MODELS INDICATE THIS RAIN
SHIELD TO CONTINUE THROUGH THE AFTERNOON ACROSS THE SOUTH WITH MORE
SCATTERED SHOWERS NORTH WHERE DRIER AIR EXISTS.
CURRENT FORECAST LOOKS TO HANDLE THIS SCENARIO DECENTLY. ADJUSTED
POPS DOWN NORTH JUST A TAD AS RAIN SHIELD IS MOVING VERY SLOWLY AND
TRIED TO ADJUST THE TIMING BETTER IN WX GRIDS. ALSO ADJUSTED HIGHS
TODAY UPWARD AS SOME HAVE ALREADY EXCEEDED THE FORECASTED HIGHS.
HOURLY TEMPS ADJUSTED AS WELL. UPDATED PRODUCTS OUT SHORTLY. /28/
&&
.AVIATION...A LOW PRESSURE SYSTEM MOVING ALONG THE GULF COAST WILL
BRING LOWERING CEILINGS AND RAIN TO MUCH OF THE AREA LATER THIS
AFTERNOON AND EVENING. MVFR RESTRICTIONS WILL GRADUALLY DEVELOP AT
HBG/MEI/JAN DURING THE MID TO LATE AFTERNOON...WITH IFR RESTRICTIONS
BECOMING POSSIBLE AT HBG/MEI DURING THE EARLY EVNG AS HEAVIER
RAINFALL ATTEMPTS TO MOVE INTO SRN PORTIONS OF THE FORECAST AREA.
INSTABILITY WILL BE MARGINAL BUT COULD SUPPORT A LITTLE TSTM
ACTIVITY AT HBG/MEI. IT LOOKS LIKE GLH/GWO/GTR WILL STAY IN VFR
CATEGORY FOR MOST OF THE RAIN EVENT GIVEN THE DRY AIR CURRENTLY IN
PLACE. AS THE UPPER LOW BEGINS TO LIFT OUT AND MOVE ACROSS THE
FORECAST AREA LATE TONIGHT AND SUNDAY MORNING...STRATUS COULD BECOME
WIDESPREAD ACROSS THE AREA RESULTING IN MVFR/IFR RESTRICTIONS AT ALL
SITES. THE STRATUS WILL HANG AROUND THROUGH SUNDAY AFTERNOON. /EC/
&&
.JAN WATCHES/WARNINGS/ADVISORIES...
MS...NONE.
LA...NONE.
AR...NONE.
&&
$$
28/EC
000
FXUS64 KJAN 210927
AFDJAN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON MS
327 AM CST SAT NOV 21 2009
.SHORT TERM...TODAY THROUGH SUNDAY NIGHT...PRIMARY FORECAST CONCERNS
FOR THIS PERIOD WILL BE RAINFALL ASSOCIATED WITH SLOWLY DEEPENING LOW
PRESSURE OVER THE GULF...ALONG WITH THE ASSOCIATED WINDS. EARLY
MORNING SURFACE ANALYSIS PLACES A 1008 MB SURFACE LOW OVER THE
NORTHWEST GULF OF MEXICO...ABOUT 120 MILES SOUTHEAST OF HOUSTON
TEXAS. THIS LOW CONTINUES TO DEVELOP AS VIGOROUS DEEP-LAYER ASCENT
DOWNSTREAM OF A SHORTWAVE TROUGH EMBEDDED WITHIN THE SOUTHERN JET
STREAM CONTINUES TO INTERACT WITH A BAROCLINIC ZONE OVER THE WESTERN
GULF. AMONG MULTI-MODEL GUIDANCE...THE GFS/NAM/SREF/UKMET APPEAR TO
INITIALIZE THE DEPTH AND POSITION OF THE LOW QUITE WELL. BY THIS
EVENING...THE NAM SHOWS THE LOW ASSUMING MORE OF A NORTHWARD HEADING
WHILE ELONGATING THE LOW FROM NORTHWEST TO SOUTHEAST...AND FOLLOWING
A TRACK SIMILAR TO THE ECMWF. TIGHT CLUSTERING AMONGST GFS ENSEMBLE
MEMBERS AROUND THE OPERATIONAL GFS/UKMET/SREF TRACK SOLUTIONS GIVES
HIGHER CREDIBILITY TOWARD THESE SOLUTIONS...AND THUS THE MORE
SOUTHERN LOW TRACK IS THE PREFERRED SOLUTION. THIS CALLS FOR THE LOW
TRACKING EAST-NORTHEASTWARD SOUTH OF THE GULF COASTLINE THROUGH
SUNDAY MORNING BEFORE MAKING LANDFALL OVER THE WESTERN FLORIDA
PANHANDLE.
GIVEN THE MORE SOUTHERN LOW TRACK...THE NORTHWARD EXTENT OF PRECIP
COVERAGE TODAY IS IN QUESTION...AND LOCAL HIGH-RES WRF ENSEMBLE
MEMBERS THAT USE PREFERRED GFS PARAMETERS AS INPUT SUGGEST THAT RAIN
COVERAGE ACROSS NORTHERN AREAS WILL NOT BE AS WIDESPREAD AS
PREVIOUSLY ANTICIPATED. THUS...POPS WERE TRENDED DOWNWARD TO LIKELY
OVER THE NORTHERN THIRD OF THE CWA...CONSISTENT WITH LATEST MAV
GUIDANCE. HOWEVER...ALL WRF MEMBERS INDICATE MEASURABLE PRECIPITATION
OCCURRING ALONG AND SOUTH OF INTERSTATE 20...WHERE POPS WERE
INCREASED ABOVE MAV GUIDANCE TO 100 PERCENT FOR TODAY. THE OTHER
IMPLICATION OF THE MORE SOUTHERN LOW TRACK IS THAT THE PROBABILITY OF
MEETING LAKE WIND ADVISORY CRITERIA ON ROSS BARNETT RESERVOIR AND
OKATIBBEE LAKE HAS DECREASED. THE TOTAL SOUTH-TO-NORTH PRESSURE
DIFFERENCE ACROSS THE CWA IS NOT EXPECTED TO EXCEED 3.5 MB TODAY OR
TONIGHT...SUPPORTING SUSTAINED NORTHEAST WINDS OF 10 TO 15 MPH ON THE
LAKES. FORECAST SOUNDINGS FROM THE GFS INDICATE MAXIMUM FLOW BELOW H7
REMAINING AT OR BELOW 25 KT...AND EVEN WINDS THIS STRONG WILL
STRUGGLE REACHING THE SURFACE AS GUSTS GIVEN STABLE THERMAL PROFILE
BELOW H7. GUSTS ARE EXPECTED TO REMAIN BELOW 25 MPH. IN FACT...WRF
ENSEMBLE NOW INDICATES LESS THAN 15 PERCENT CHANCE OF LAKE WIND
ADVISORY CRITERIA BEING MET ON THE LAKES...AND THUS THE ADVISORY HAS
BEEN CANCELLED. THE STRONGER LOW-LEVEL WIND FIELD SUGGESTED BY THE
NAM APPEARS UNLIKELY GIVEN THE ANTICIPATED SOUTHERN LOW TRACK.
ADDITIONALLY...ELEVATED INSTABILITY SUPPORTING MUCAPES FROM 200 TO
500 J/KG WILL AFFECT THE SOUTHEASTERN THIRD OF THE FORECAST AREA THIS
AFTERNOON AND EVENING...WHERE ISOLATED THUNDERSTORMS ARE POSSIBLE.
NEAR ZERO SBCAPES WILL PRECLUDE PRESENCE OF SURFACE-BASED CONVECTION
OR RISK FOR STRONG THUNDERSTORMS. HIGH TEMPERATURES TODAY MOSTLY
FOLLOWED MAV GUIDANCE...THOUGH THEY WERE RAISED A COUPLE DEGREES
ACROSS NORTHERN AREAS...WHERE ONSET OF RAIN WILL BE THE LATEST.
FOR TONIGHT...RAIN WILL CONTINUE TO SPREAD ACROSS THE EASTERN HALF
OF THE CWA...WHERE POPS HAVE BEEN RAISED ABOVE MAV GUIDANCE TO 100
PERCENT WITH HIGH CONFIDENCE OF MEASURABLE PRECIP FROM THE SREF.
TOTAL RAINFALL AMOUNTS THROUGH TONIGHT OF ONE-HALF TO ONE INCH ARE
EXPECTED...WHICH WILL BE TOO LOW FOR FLASH FLOODING. MEANWHILE...
DRIER AIR WRAPPING INTO THE SOUTHWESTERN SEMICIRCLE OF THE LOW WILL
LIMIT PRECIP CHANCES OVER THE SOUTHWESTERN CWA...WHERE RAIN IS
EXPECTED TO END DURING THE EVENING. ON SUNDAY...THE SURFACE LOW WILL
BEGIN FILLING AS THE SUPPORTING MID/UPPER-LEVEL SHORTWAVE TROUGH
BECOMES ABSORBED INTO THE LARGE-SCALE JET STREAM AND DECOUPLES FROM
THE SURFACE CIRCULATION. AS SUCH...PRECIP CHANCES AND WIND SPEEDS
WILL DECREASE...THOUGH ENOUGH MOISTURE WEST OF THE LOW WILL SUPPORT
A CHANCE FOR RAIN OVER EASTERN AREAS SUNDAY MORNING PER MAV
GUIDANCE. BY SUNDAY EVENING...MOST OF THE RAIN IS EXPECTED TO HAVE
TAPERED OFF. SKIES WILL BEGIN CLEARING FROM SOUTHWEST TO NORTHEAST
ON SUNDAY...AND THUS TEMPS WERE INCREASED A COUPLE DEGREES ABOVE MAV
GUIDANCE ACROSS THE SOUTHWEST. THEN FOR SUNDAY NIGHT...CLEARING
SKIES COMBINED WITH THE MOIST GROUND WILL SET THE STAGE FOR PATCHY
FOG DEVELOPMENT...PARTICULARLY ACROSS THE SOUTHERN PORTION OF THE
CWA WHERE HIGHEST RAINFALL TOTALS THROUGH SUNDAY ARE EXPECTED.
/COHEN/
.LONG TERM...A RATHER FLAT ZONAL FLOW PATTERN WILL TRANSITION BACK TO
RIDGING IN THE WRN CONUS AND TROUGHING IN THE E DURING THE COMING
HOLIDAY WEEK. THE PRIMARY FEATURE FOR THE WEEK APPEARS TO BE A WEAK
FRONTAL SYSTEM PASSING THROUGH THE LOWER MS VALLEY TUESDAY AND
TUESDAY NIGHT WITH MINIMAL RAINFALL CHANCES. THIS BOUNDARY IS
FOLLOWED BY TWO REINFORCING TROUGHS WEDNESDAY NIGHT AND LATER ON
SATURDAY TO KEEP US COOLER THAN CLIMATOLOGY.
QUITE MILD CONDITIONS BEGIN THE WEEK ON MONDAY WITH FOGGY LOWS IN
THE 40S AND HIGHS RECOVERING NICELY INTO THE M-U60S WITH CONSIDERABLE
SUNSHINE. THE GFS IS NOW MUSTERING UP 0.75-1.0 INCH PWATS ALONG THE
TUESDAY FRONT BEFORE RETURNING TO 0.25 INCHES ON WEDNESDAY. PRE
FRONTAL LOW LEVEL RIDGING ALONG THE GULF COAST SHOULD PREVENT MUCH
MOISTURE RETURN AND DO NOT SEE MUCH MOISTURE CONVERGENCE WITH THE
BOUNDARY SO WILL KEEP MENTION TO LIGHT RAIN. THE ECMWF IS ACTUALLY A
LITTLE WETTER WITH THIS FRONT AS IT SHOWS A TENTH OF AN INCH QPFS
HANGING ON INTO TUESDAY EVENING OVER THE SERN PORTIONS OF OUR CWFA.
BEYOND THAT...A QUICK REINFORCING DRY TROUGH SWEEPS THROUGH THE AREA
WITH A FEW CLOUDS FOR WEDNESDAY NIGHT. THIS SETS UP A CHILLY CAA
CELEBRATION FOR THANKSGIVING DAY WITH MOST LOWS IN THE U30S AND HIGHS
IN THE 50S.
A 1020+MB SURFACE HIGH OVER SERN TX FRIDAY MOVES ALONG THE GULF COAST
FOR FRIDAY NIGHT AND SATURDAY WITH SOME MOISTURE RETURN FOR SATURDAY
NIGHT. ANOTHER WEAK FRONT COULD REACH THE AREA BY THAT TIME BUT IT
ALSO IS APPEARING RATHER DRY WITH THE SURFACE HIGH OFF THE COAST OF
NW FL. WILL HAVE TO MONITOR THIS TIME FRAME AS THE ECMWF AGAIN A
LITTLE MORE ROBUST WITH THE MASS FIELDS AND HIGHER RAIN CHANCES.
ALL IN ALL...THE HOLIDAY WEEK SHOULD BE QUITE DRY AND ALSO SEASONABLE
IN THE TEMPERATURE DEPARTMENT. THE ENSEMBLE MOS GUIDANCE STAYS WITHIN
1-2 STANDARD DEVIATIONS AND IN MOST CASES THE MEANS ARE CLOSE TO THE
OPERATIONAL NUMBERS./40/
&&
.AVIATION...RAIN WILL SPREAD FROM SOUTHWEST TO NORTHEAST ACROSS THE
AREA TODAY...AS AN UPPER LEVEL DISTURBANCE AND SURFACE LOW PRESSURE
APPROACH THE REGION. RAINFALL INTENSITY IS EXPECTED TO BE LIGHT TO
MODERATE...WITH THE GREATEST COVERAGE OF RAIN ACROSS CENTRAL AND
SOUTHERN MISSISSIPPI TODAY. FOR TONIGHT...THE GREATEST COVERAGE OF
RAIN WILL BE ACROSS EASTERN MISSISSIPPI. MVFR CONDITIONS DUE TO
CEILING RESTRICTIONS AND OCCASIONAL VISIBILITY RESTRICTIONS WILL
AFFECT MUCH OF THE AREA BY THIS AFTERNOON...WITH OCCASIONAL IFR
CEILINGS AND VISIBILITIES POSSIBLE AT KHBG AND KMEI NEAR THE MODERATE
RAIN. AN ISOLATED THUNDERSTORM WILL ALSO BE POSSIBLE ACROSS SOUTHEAST
MISSISSIPPI THIS AFTERNOON AND EVENING...THOUGH THE CHANCE OF
THUNDERSTORMS OCCURRING AT ANY TAF SITE IS TOO LOW FOR MENTION IN THE
TAFS AT THIS TIME. NORTHEAST TO EAST WINDS ARE EXPECTED TO INCREASE
TO 7 TO 12 KT BY THIS AFTERNOON...BUT WILL SLOWLY DIMINISH LATE
TONIGHT. /COHEN/
&&
.PRELIMINARY POINT TEMPS/POPS...
JACKSON 57 49 61 45 / 100 83 15 9
MERIDIAN 57 47 62 44 / 100 98 35 15
VICKSBURG 58 47 62 42 / 100 48 15 7
HATTIESBURG 59 49 64 46 / 100 96 15 9
NATCHEZ 56 48 63 43 / 100 47 10 3
GREENVILLE 59 47 62 44 / 59 50 15 7
GREENWOOD 60 47 61 44 / 62 89 30 10
&&
.JAN WATCHES/WARNINGS/ADVISORIES...
MS...NONE.
LA...NONE.
AR...NONE.
&&
$$
000
FXUS64 KJAN 210229
AFDJAN
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE JACKSON MS
825 PM CST FRI NOV 20 2009
.UPDATE...LATEST SATELLITE IMAGERY SHOWED A SHORT WAVE OVER THE SOUTHERN
PLAINS WITH AN ASSOCIATED SURFACE WAVE OVER THE NORTHWEST GULF OF
MEXICO. THE ARKLAMISS WAS WELL NORTH IN THE COOLER AND STABLE
AIRMASS. AREA RADARS WERE PICKING UP SOME PATCHY VERY LIGHT RAIN
TO THE WEST AND SOUTH OF THE REGION. STILL EXPECT SOME VERY LIGHT
RAIN TO IMPACT THE REGION LATER TONIGHT FROM THE SOUTH. THIS WILL
NOT BE A SHOWERY TYPE SYSTEM FOR THIS REGION IN THIS COOL STABLE
AIRMASS. SO FOLLOWING RADAR TRENDS OF DEVELOPMENT. HAVE PUSHED BACK THE
FIRST WAVE OF VERY LIGHT RAIN IN THE SOUTH UNTIL NEAR MIDNIGHT...THEN PUT
PULLED BACK RAIN CHANCES FOR THE REST OF THE NIGHT. GOING FROM A SLIGHT
CHANCE ALONG AND NORTH OF INTERSTATE 20 TO CHANCE POPS SOUTH. ALSO DELAYED
HIGH POPS UNTIL THE LATER HALF OF SATURDAY MORNING FOR THE REGION.
CURRENT LOWS IN THE 40S LOOKS TO BE ON TRACK. WILL KEEP THE BEST
CHANCE POPS ACROSS THE SOUTH HALF WHERE THE LIGHT RAIN WILL
ORIGINATE FROM./17/
.PREV DISCUSSION...352 PM CST FRI NOV 20 2009
.SHORT TERM...TONIGHT THROUGH SUNDAY NIGHT...PRIMARY CONCERN THIS
PERIOD REVOLVES AROUND WIND SPEEDS AND PRECIP ACCUMULATIONS THROUGH
SUNDAY AFTERNOON.
THIN UPPER LEVEL CLOUD COVER IS ON THE INCREASE THIS AFTERNOON AHEAD
OF A S/WV TROUGH CROSSING THE RIO GRANDE VALLEY. THIS S/WV WILL
DEEPEN AN AREA OF SFC LOW PRESSURE LOCATED OVER THE WESTERN GULF OF
MEXICO AS IT ADVANCES EAST THROUGH THE NIGHT TONIGHT. AS A
RESULT...PRECIP CHANCES WILL INCREASE FROM THE SW OVERNIGHT AS THE
SFC LOW TRANSLATES TOWARD THE LA COAST. SOME DIFFERENCES EMERGE
AMONG THE NWP GUIDANCE AT THIS POINT CALLING THE EVENTUAL
PROGRESSION OF THIS SYSTEM INTO QUESTION. THE GFS REMAINS ON THE
FAST EDGE OF THE ENVELOPE THROUGH THE WEEKEND AND MAINTAINS A WEAKER
MORE PERSISTENT SFC LOW RIGHT ALONG THE COAST. THE ECMWF DEVELOPS A
MUCH DEEPER SURFACE LOW WITH SOME UNUSUAL BULLS EYES IN THE PRECIP
FIELDS LIKELY ASSOCIATED WITH GRID SCALE FEEDBACK PROBLEMS. SREF
CAME IN MORE WITH THE GFS IN TERMS OF SURFACE LOW TRACK ALTHOUGH WAS
NOT AS FAST PUSHING THE LOW INTO THE AL COAST. FOR THIS
PACKAGE...LEANED MORE ON THE SREF IN TERMS OF OVERALL SPEED OF THE
SYSTEM WITH A GFS/ECMWF/SREF BLEND FOR THE TRACK. THIS DID MEAN SOME
DIVERGENCE FROM THE 12Z MAV GUIDANCE POPS...PRIMARILY ON SATURDAY
AFTERNOON/NIGHT WHERE ALL AREAS GOT BUMPED ABOVE GUIDANCE. GFS
REALLY KEEPS THE RAIN ISOLATED SE OF THE NATCHEZ TRACE. THIS IS NOT
SUPPORTED BY THE ECMWF OR SREF WHICH BOTH SHOW MEASURABLE RAINFALL
ACROSS THE AREA DURING THESE TIMES. DO FEEL THE HEAVIEST RAINFALL
WILL BE SE OF THE TRACE...BUT NOT LIMITED TO THIS AREA.
AT THIS POINT...HEAVY RAINFALL WARRANTING ANY FLOOD PRODUCTS IS NOT
NEEDED AS PW VALUES STRUGGLE TO CLIMB ABOVE 1.25 IN...EVEN ACROSS
SOUTHEASTERN AREAS. RAINFALL TOTALS ON THE ORDER OF 0.50 TO 1 INCH
ARE PROBABLE ACROSS THE CWA WITH THE HIGHEST AMOUNTS SE OF THE
TRACE. THAT BEING SAID...LOCALIZED AREAS RECEIVING A LITTLE OVER AN
INCH IS NOT OUT OF THE QUESTION. EASTERLY WINDS ARE STILL EXPECTED
TO INCREASE TOMORROW AFTERNOON AS THE SFC LOW NEARS. STRONGEST WINDS
WILL BE LIMITED TO AREAS S AND E...AND WILL GO AHEAD AND ISSUE A
LAKE WIND ADVISORY FOR THE ROSS BARNETT RES AND LAKE OKATIBBEE
STARTING LATE TOMORROW MORNING. THIS IS A MARGINAL EVENT CONSIDERING
THE SYNOPTIC SET-UP AND WILL BE WATCHED CLOSELY FOR POSSIBLE
TEMPORAL AND AREAL CHANGES AS THIS SYSTEM EVOLVES. IN ADDITION...
WENT AHEAD AND LEFT A SLIGHT CHANCE OF A THUNDERSTORM OR TWO
DEVELOPING ACROSS SERN AREAS TOMORROW AFTERNOON INTO THE EARLY
EVENING. GFS HINTS AT 100-200 J/KG OF MUCAPE SLIDING ACROSS THE AREA
AS THE LOW MAKES ITS CLOSEST POINT OF APPROACH AND COUPLED WITH DEEP
LAYER LIFT IN PLACE AHEAD OF THE UPPER LEVEL S/WV...FEEL THE CHANCES
ARE NON-ZERO.
PRECIP WILL CONTINUE INTO THE OVERNIGHT HOURS SAT NIGHT BEFORE
BEGINNING TO TAPER OFF FROM W TO E LATE SUN MORNING INTO THE
AFTERNOON AS THE BEST LIFT AND LOW LEVEL MOISTURE FEED MOVE INTO AL.
S/WV RIDGING AND SFC HIGH PRESSURE MOVE INTO THE ARKLAMISS LATE
SUNDAY AND SHOULD PROVIDE SOME CLOUD CLEARING AS A RESULT. WINDS
LOOK TO GO VERY LIGHT OR EVEN CALM MONDAY NIGHT...AND CONSIDERING
THE LACK OF A COOL/DRY PUSH AND RESIDUAL SFC MOISTURE FROM THE
RAINS, ADDED SOME PATCHY FOG FOR MONDAY MORNING.
MAV TEMPS LOOKED GOOD EXCEPT FOR SUN AFTERNOON HIGHS WHERE GFS
APPEARED TOO WARM CONSIDERING THE LINGERING RAIN AND CLOUD COVER.
WENT AHEAD AND LOWERED TEMPS A DEGREE OR TWO AREAWIDE AT THAT TIME.
/BK/
.PREVIOUS LONG TERM...FOR MID- TO LATE-WEEK...A SERIES OF SHORTWAVE
TROUGHS AND ASSOCIATED SURFACE COLD FRONTS WILL DIVE SOUTHEASTWARD
ACROSS THE MIDWEST AND OHIO VALLEY REGIONS...CARVING OUT A MEAN
TROUGH OVER THE EASTERN CONUS. NWP MODEL GUIDANCE HAS COME INTO
BETTER AGREEMENT IN DROPPING ONE OF THESE COLD FRONTS SOUTHWARD
ACROSS THE REGION ON TUESDAY. THE FRONT WILL BECOME MORE SHALLOW AS
IT APPROACHES AND MOVES ACROSS THE ARKLAMISS AS THE ASSOCIATED UPPER
TROUGH AND STRONGER DEEP-LAYER SYNOPTIC-SCALE ASCENT REMAIN WELL
NORTH OF THE AREA. NEVERTHELESS... MOISTURE POOLING ALONG THE
BOUNDARY RESULTING IN PWATS NEAR ONE INCH WILL BE SUFFICIENT FOR
ISOLATED LIGHT SHOWERS ALONG OR JUST BEHIND THE SURFACE FRONT...ALONG
WITH AN INCREASE IN CLOUDS. POPS WERE LOWERED FROM MEX GUIDANCE TO
SLIGHT CHANCE FOR LATE MONDAY NIGHT OVER NORTHWESTERN AREAS...AS THE
OPERATIONAL GFS APPEARS TO MOVE THE FRONT TOO QUICKLY TO THE SOUTH
RELATIVE TO GFS ENSEMBLE MEMBERS AND ECMWF...AND WITH WEAK UPPER
SUPPORT OVER THE ARKLAMISS. BEHIND THE FRONT...WINDS WILL BECOME
NORTHERLY AND ADVECT COOLER AIR ACROSS THE REGION...WITH HIGH
PRESSURE BUILDING IN THE WAKE OF THE FRONT.
FOR WEDNESDAY NIGHT OR THURSDAY...A REINFORCING COLD FRONT WILL
QUICKLY SURGE SOUTH ACROSS THE REGION...THOUGH DEEP-LAYER DRY AIR
WILL BE IN PLACE /PWATS OF ONLY 0.3 INCHES/ PRECLUDING PRECIP CHANCES
WITH THIS FRONT. THE ONLY IMPACTS TO SENSIBLE WEATHER WITH THE FRONT
WILL BE AN INCREASE IN NORTH WINDS ALONG WITH THE POTENTIAL FOR MUCH
COOLER CONDITIONS LATE IN THE WEEK. THE CORE OF THE COLD AIRMASS
WILL REMAIN NORTH OF THE CWA...THOUGH GFS AND ECMWF INDICATE 850-MB
TEMPS FALLING TO 3C ACROSS NORTHERN AREAS BEHIND THE FRONT...
POTENTIALLY SUPPORTING TEMPERATURES SEVERAL DEGREES BELOW SEASONAL
AVERAGES. HOWEVER...SIGNIFICANT DIFFERENCES BETWEEN GFS AND ECMWF IN
THE CHARACTERISTICS OF THE ASSOCIATED UPPER TROUGH SUGGEST LOW
CONFIDENCE IN THE TIMING OF THE CORRESPONDING SURFACE FRONT...AS
WELL AS HOW COLD TEMPERATURES GET. /COHEN/
&&
.AVIATION...A LOW PRESSURE SYSTEM APPROACHING FROM THE WEST KEPT
THE CIRRUS SHIELD OVER THE REGION FOR THIS EVENING. THIS CLOUD DECK
WILL GRADUALLY LOWER TONIGHT...BUT CEILINGS SHOULD REMAIN ABOVE 8000
FT THROUGH THE NIGHT GIVEN THE VERY DRY LOW LEVEL AIR IN PLACE. AS
RAIN DEVELOPS OVER THE AREA NORTH OF A WARM FRONT...CEILINGS AND
VISIBILITY WILL DETERIORATE...ESPECIALLY AT JAN/HBG/MEI WHERE IFR
CEILINGS MAY BECOME PREVALENT PRIOR TO NOON SATURDAY. ALL SITES
COULD EXPERIENCE MVFR/IFR RESTRICTIONS DUE TO LOWER CEILINGS AND
RAIN AS WE GO INTO SATURDAY AFTN/NIGHT. GREATER INSTABILITY IN THE
MEI/HBG AREA WILL SUPPORT A FEW TSTMS FROM SATURDAY AFTERNOON INTO
SATURDAY EVENING. /17/
&&
.PRELIMINARY POINT TEMPS/POPS...
JACKSON 46 58 45 61 / 22 89 63 13
MERIDIAN 44 57 45 61 / 22 86 80 24
VICKSBURG 46 58 45 62 / 22 89 58 9
HATTIESBURG 48 58 49 63 / 49 90 56 12
NATCHEZ 47 57 44 63 / 47 90 45 5
GREENVILLE 46 60 44 63 / 18 80 69 13
GREENWOOD 45 60 45 62 / 13 83 80 19
&&
.JAN WATCHES/WARNINGS/ADVISORIES...
MS...LAKE WIND ADVISORY FROM 9 AM SATURDAY TO MIDNIGHT CST SATURDAY
NIGHT FOR MSZ043-049-052.
LA...NONE.
AR...NONE.
&&
$$
000
FXUS64 KJAN 202152
AFDJAN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON MS
352 PM CST FRI NOV 20 2009
.SHORT TERM...TONIGHT THROUGH SUNDAY NIGHT...PRIMARY CONCERN THIS
PERIOD REVOLVES AROUND WIND SPEEDS AND PRECIP ACCUMULATIONS THROUGH
SUNDAY AFTERNOON.
THIN UPPER LEVEL CLOUD COVER IS ON THE INCREASE THIS AFTERNOON AHEAD
OF A S/WV TROUGH CROSSING THE RIO GRANDE VALLEY. THIS S/WV WILL
DEEPEN AN AREA OF SFC LOW PRESSURE LOCATED OVER THE WESTERN GULF OF
MEXICO AS IT ADVANCES EAST THROUGH THE NIGHT TONIGHT. AS A
RESULT...PRECIP CHANCES WILL INCREASE FROM THE SW OVERNIGHT AS THE
SFC LOW TRANSLATES TOWARD THE LA COAST. SOME DIFFERENCES EMERGE
AMONG THE NWP GUIDANCE AT THIS POINT CALLING THE EVENTUAL
PROGRESSION OF THIS SYSTEM INTO QUESTION. THE GFS REMAINS ON THE
FAST EDGE OF THE ENVELOPE THROUGH THE WEEKEND AND MAINTAINS A WEAKER
MORE PERSISTENT SFC LOW RIGHT ALONG THE COAST. THE ECMWF DEVELOPS A
MUCH DEEPER SURFACE LOW WITH SOME UNUSUAL BULLS EYES IN THE PRECIP
FIELDS LIKELY ASSOCIATED WITH GRID SCALE FEEDBACK PROBLEMS. SREF
CAME IN MORE WITH THE GFS IN TERMS OF SURFACE LOW TRACK ALTHOUGH WAS
NOT AS FAST PUSHING THE LOW INTO THE AL COAST. FOR THIS
PACKAGE...LEANED MORE ON THE SREF IN TERMS OF OVERALL SPEED OF THE
SYSTEM WITH A GFS/ECMWF/SREF BLEND FOR THE TRACK. THIS DID MEAN SOME
DIVERGENCE FROM THE 12Z MAV GUIDANCE POPS...PRIMARILY ON SATURDAY
AFTERNOON/NIGHT WHERE ALL AREAS GOT BUMPED ABOVE GUIDANCE. GFS
REALLY KEEPS THE RAIN ISOLATED SE OF THE NATCHEZ TRACE. THIS IS NOT
SUPPORTED BY THE ECMWF OR SREF WHICH BOTH SHOW MEASURABLE RAINFALL
ACROSS THE AREA DURING THESE TIMES. DO FEEL THE HEAVIEST RAINFALL
WILL BE SE OF THE TRACE...BUT NOT LIMITED TO THIS AREA.
AT THIS POINT...HEAVY RAINFALL WARRANTING ANY FLOOD PRODUCTS IS NOT
NEEDED AS PW VALUES STRUGGLE TO CLIMB ABOVE 1.25 IN...EVEN ACROSS
SOUTHEASTERN AREAS. RAINFALL TOTALS ON THE ORDER OF 0.50 TO 1 INCH
ARE PROBABLE ACROSS THE CWA WITH THE HIGHEST AMOUNTS SE OF THE
TRACE. THAT BEING SAID...LOCALIZED AREAS RECEIVING A LITTLE OVER AN
INCH IS NOT OUT OF THE QUESTION. EASTERLY WINDS ARE STILL EXPECTED
TO INCREASE TOMORROW AFTERNOON AS THE SFC LOW NEARS. STRONGEST WINDS
WILL BE LIMITED TO AREAS S AND E...AND WILL GO AHEAD AND ISSUE A
LAKE WIND ADVISORY FOR THE ROSS BARNETT RES AND LAKE OKATIBBEE
STARTING LATE TOMORROW MORNING. THIS IS A MARGINAL EVENT CONSIDERING
THE SYNOPTIC SET-UP AND WILL BE WATCHED CLOSELY FOR POSSIBLE
TEMPORAL AND AREAL CHANGES AS THIS SYSTEM EVOLVES. IN ADDITION...
WENT AHEAD AND LEFT A SLIGHT CHANCE OF A THUNDERSTORM OR TWO
DEVELOPING ACROSS SERN AREAS TOMORROW AFTERNOON INTO THE EARLY
EVENING. GFS HINTS AT 100-200 J/KG OF MUCAPE SLIDING ACROSS THE AREA
AS THE LOW MAKES ITS CLOSEST POINT OF APPROACH AND COUPLED WITH DEEP
LAYER LIFT IN PLACE AHEAD OF THE UPPER LEVEL S/WV...FEEL THE CHANCES
ARE NON-ZERO.
PRECIP WILL CONTINUE INTO THE OVERNIGHT HOURS SAT NIGHT BEFORE
BEGINNING TO TAPER OFF FROM W TO E LATE SUN MORNING INTO THE
AFTERNOON AS THE BEST LIFT AND LOW LEVEL MOISTURE FEED MOVE INTO AL.
S/WV RIDGING AND SFC HIGH PRESSURE MOVE INTO THE ARKLAMISS LATE
SUNDAY AND SHOULD PROVIDE SOME CLOUD CLEARING AS A RESULT. WINDS
LOOK TO GO VERY LIGHT OR EVEN CALM MONDAY NIGHT...AND CONSIDERING
THE LACK OF A COOL/DRY PUSH AND RESIDUAL SFC MOISTURE FROM THE
RAINS, ADDED SOME PATCHY FOG FOR MONDAY MORNING.
MAV TEMPS LOOKED GOOD EXCEPT FOR SUN AFTERNOON HIGHS WHERE GFS
APPEARED TOO WARM CONSIDERING THE LINGERING RAIN AND CLOUD COVER.
WENT AHEAD AND LOWERED TEMPS A DEGREE OR TWO AREAWIDE AT THAT TIME.
/BK/
.PREVIOUS LONG TERM...FOR MID- TO LATE-WEEK...A SERIES OF SHORTWAVE
TROUGHS AND ASSOCIATED SURFACE COLD FRONTS WILL DIVE SOUTHEASTWARD
ACROSS THE MIDWEST AND OHIO VALLEY REGIONS...CARVING OUT A MEAN
TROUGH OVER THE EASTERN CONUS. NWP MODEL GUIDANCE HAS COME INTO
BETTER AGREEMENT IN DROPPING ONE OF THESE COLD FRONTS SOUTHWARD
ACROSS THE REGION ON TUESDAY. THE FRONT WILL BECOME MORE SHALLOW AS
IT APPROACHES AND MOVES ACROSS THE ARKLAMISS AS THE ASSOCIATED UPPER
TROUGH AND STRONGER DEEP-LAYER SYNOPTIC-SCALE ASCENT REMAIN WELL
NORTH OF THE AREA. NEVERTHELESS... MOISTURE POOLING ALONG THE
BOUNDARY RESULTING IN PWATS NEAR ONE INCH WILL BE SUFFICIENT FOR
ISOLATED LIGHT SHOWERS ALONG OR JUST BEHIND THE SURFACE FRONT...ALONG
WITH AN INCREASE IN CLOUDS. POPS WERE LOWERED FROM MEX GUIDANCE TO
SLIGHT CHANCE FOR LATE MONDAY NIGHT OVER NORTHWESTERN AREAS...AS THE
OPERATIONAL GFS APPEARS TO MOVE THE FRONT TOO QUICKLY TO THE SOUTH
RELATIVE TO GFS ENSEMBLE MEMBERS AND ECMWF...AND WITH WEAK UPPER
SUPPORT OVER THE ARKLAMISS. BEHIND THE FRONT...WINDS WILL BECOME
NORTHERLY AND ADVECT COOLER AIR ACROSS THE REGION...WITH HIGH
PRESSURE BUILDING IN THE WAKE OF THE FRONT.
FOR WEDNESDAY NIGHT OR THURSDAY...A REINFORCING COLD FRONT WILL
QUICKLY SURGE SOUTH ACROSS THE REGION...THOUGH DEEP-LAYER DRY AIR
WILL BE IN PLACE /PWATS OF ONLY 0.3 INCHES/ PRECLUDING PRECIP CHANCES
WITH THIS FRONT. THE ONLY IMPACTS TO SENSIBLE WEATHER WITH THE FRONT
WILL BE AN INCREASE IN NORTH WINDS ALONG WITH THE POTENTIAL FOR MUCH
COOLER CONDITIONS LATE IN THE WEEK. THE CORE OF THE COLD AIRMASS
WILL REMAIN NORTH OF THE CWA...THOUGH GFS AND ECMWF INDICATE 850-MB
TEMPS FALLING TO 3C ACROSS NORTHERN AREAS BEHIND THE FRONT...
POTENTIALLY SUPPORTING TEMPERATURES SEVERAL DEGREES BELOW SEASONAL
AVERAGES. HOWEVER...SIGNIFICANT DIFFERENCES BETWEEN GFS AND ECMWF IN
THE CHARACTERISTICS OF THE ASSOCIATED UPPER TROUGH SUGGEST LOW
CONFIDENCE IN THE TIMING OF THE CORRESPONDING SURFACE FRONT...AS
WELL AS HOW COLD TEMPERATURES GET. /COHEN/
&&
.AVIATION...A LOW PRESSURE SYSTEM APPROACHING FROM THE WEST IS
SENDING A CIRRUS SHIELD INTO THE AREA TODAY. THIS CLOUD DECK WILL
GRADUALLY LOWER TONIGHT...BUT CEILINGS SHOULD REMAIN ABOVE 8000 FT
THROUGH THE NIGHT GIVEN THE VERY DRY LOW LEVEL AIR IN PLACE. AS RAIN
DEVELOPS OVER THE AREA NORTH OF A WARM FRONT...CEILINGS AND
VISIBILITY WILL DETERIORATE...ESPECIALLY AT HBG/MEI WHERE IFR
CEILINGS MAY BECOME PREVALENT PRIOR TO NOON SATURDAY. ALL SITES
COULD EXPERIENCE MVFR/IFR RESTRICTIONS DUE TO LOWER CEILINGS AND
RAIN AS WE GO INTO SATURDAY AFTN/NIGHT. GREATER INSTABILITY IN THE
HBG AREA WILL SUPPORT A FEW TSTMS FROM LATE SAT MORNING INTO SAT
AFTN. /EC/
&&
.PRELIMINARY POINT TEMPS/POPS...
JACKSON 46 58 45 61 / 43 89 63 13
MERIDIAN 44 57 45 61 / 41 86 80 24
VICKSBURG 46 58 45 62 / 39 89 58 9
HATTIESBURG 48 58 49 63 / 52 90 56 12
NATCHEZ 47 57 44 63 / 52 90 45 5
GREENVILLE 46 60 44 63 / 18 80 69 13
GREENWOOD 45 60 45 62 / 13 83 80 19
&&
.JAN WATCHES/WARNINGS/ADVISORIES...
MS...LAKE WIND ADVISORY FROM 9 AM SATURDAY TO MIDNIGHT CST SATURDAY
NIGHT FOR MSZ043-049-052.
LA...NONE.
AR...NONE.
&&
$$
BK/COHEN/EC
000
FXUS64 KJAN 201548
AFDJAN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON MS
948 AM CST FRI NOV 20 2009
.UPDATE...OFF TO A SLIGHTLY WARMER START THIS MORNING DESPITE THE
INCREASING HIGH CLOUDS FROM THE SOUTHWEST. INCREASED DAYTIME HIGHS A
DEGREE OR TWO AT MOST SITES BASED ON THE QUICKER WARMING TREND NOTED.
ALSO INCREASED CLOUD COVER BASED ON LATEST SATELLITE IMAGES. REST OF
THE FORECAST REMAINS ON TRACK WITH INCREASING CLOUD COVER AREAWIDE
AND PRECIP CHANCES STARTING OVER EXTREME SOUTHWEST PORTIONS OF THE
ARKLAMISS LATE THIS AFTERNOON INTO THIS EVENING. UPDATES HAVE BEEN
POSTED. /BK/
&&
.PREV DISCUSSION... /ISSUED 500 AM CST FRI NOV 20 2009/
DISCUSSION...
TODAY THROUGH SATURDAY NIGHT...
AREAS OF FROST THIS MORNING WILL BE THE LAST FOR A WHILE AS THE
EFFECTS OF THE NEXT RAIN MAKER BEGIN TO TAKE SHAPE OVER THE AREA.
WEAK ASCENT WILL DEVELOP IN WEAK WAVES THAT TRAVEL INTO THE REGION
IN SWLY FLOW ALOFT TODAY...RESULTING IN MID/HIGH CLOUDS LIFTING INTO
THE ARKLAMISS. SURFACE HIGH PRESSURE WILL CONTINUE TO LIFT OUT TO
OUR NE WHILE A SURFACE LOW UPSTREAM TRACKS INTO THE WRN GULF.
LOCATIONS IN THE FAR SW CORNER OF THE REGION WILL SEE A SLIGHT
CHANCE OF LIGHT RAIN LATE IN THE AFTERNOON BEFORE RAIN CHANCES
INCREASE TONIGHT.
THE UPPER LOW WILL PIVOT INTO ERN TX TONIGHT. THE ASSOCIATED SURFACE
LOW WILL TRACK TO THE EAST ACROSS THE NRN GULF WITH DIFFERING
SOLUTIONS FROM EACH MODEL REGARDING ITS EVENTUAL EVOLUTION. THE
FORECAST WILL BE A BIT TRICKY FOR THIS FEATURE WITH DISCREPANCIES
NOTED BETWEEN THE MODELS AND IN SOME CASES RUN TO RUN DISCREPANCIES
WITHIN A SINGLE MODEL. GENERALLY FOLLOWED GFS MOS POPS FOR THE
SHORT TERM...CUTTING POPS A BIT FROM THE NE FOR TONIGHT AND
INCREASING POPS SLIGHTLY FOR THE SE SATURDAY NIGHT. ALTHOUGH MODEL
DISCREPANCIES EXIST REGARDING THE EXACT POSITION OF FEATURES IN THE
SHORT TERM...THEY GENERALLY AGREE THAT PRECIP IS LIKELY FOR THE
REGION IN THE SHORT TERM. CONSIDERING BOTH THE SLOWER MODEL
SOLUTIONS AND THE NEWD TRACK OF THE SURFACE LOW WITH THE FASTER
MODELS...THE FORECAST WILL MAINTAIN GOOD RAIN CHANCES INTO SATURDAY
NIGHT PER GFS MOS NUMBERS FOR THE AREA.
BROAD ASCENT WILL INCREASE SATURDAY AS THE UPPER TROUGH APPROACHES.
HAVE ADDED TSTMS TO THE FORECAST FOR SATURDAY AND SATURDAY NIGHT AS
BOTH THE GFS AND EURO INDICATE ELEVATED INSTABILITY OVER THE AREA.
LOW LEVEL HELICITY AND DEEP LAYER SHEAR FIELDS ARE FORECAST TO
INTENSIFY FOR SATURDAY...INTRODUCING THE POSSIBILITY OF A FEW STRONG
THUNDERSTORMS FOR AREAS EAST OF THE NATCHEZ TRACE. GUSTY WIND WILL
ALSO DEVELOP DURING THE DAY SATURDAY AS THE SURFACE LOW TRACKS TO
THE EAST AND THE LOW LEVEL JET INCREASES. WILL NOT MENTION EITHER IN
THE HWO FOR NOW. HOWEVER A LAKE WIND ADVISORY MAY BE REQUIRED FOR
SATURDAY DEPENDING ON THE TRACK OF THE SURFACE LOW.
SUNDAY THROUGH FRIDAY...
BY 1200 UTC SUNDAY...LARGE SPREAD EXISTS AMONGST NWP MODEL GUIDANCE
WITH REGARD TO THE POSITION OF THE SURFACE LOW...AROUND 1009 MB.
MOST PERTURBATIONS OF THE GFS ENSEMBLE...AS WELL AS THE OPERATIONAL
GFS...CLUSTER THE LOW AROUND CENTRAL OR SOUTHERN ALABAMA AT THIS
TIME...CONSISTENT WITH THE NAM. THESE MODELS INDICATE MOISTURE
WRAPPING AROUND THE LOW...WITH THE OPERATIONAL GFS SHOWING A SUBTLE
SURFACE CONFLUENCE AXIS EXTENDING WEST OF THE SURFACE LOW. LOW LEVEL
CONVERGENCE NEAR THESE FEATURES WOULD SUPPORT RAIN CONTINUING OVER
THE NORTHEASTERN CWA ON SATURDAY...WHILE DRIER AIR WRAPPING INTO THE
SOUTHERN SEMICIRCLE OF THE LOW WOULD REDUCE PRECIP CHANCES
ELSEWHERE. THE UKMET AND ECMWF ARE AT THE SOUTHERN AND WESTERN
EXTENT OF THE GUIDANCE ENVELOPE WITH REGARD TO THE POSITION OF THE
SURFACE LOW...KEEPING HIGHER PRECIP CHANCES ACROSS MUCH OF THE AREA
THROUGH THE DAY. GIVEN CONTRACTING WAVELENGTH OF SUPPORTING UPPER
TROUGH...THE MORE PROGRESSIVE GFS/NAM SOLUTION IS PREFERRED...AND
MAV POPS WERE FOLLOWED FOR SUNDAY. HOWEVER...SHOULD THE UPPER LOW
DISCONNECT SOME FROM THE SOUTHERN STREAM AND SLOW DOWN...THEN THE
SLOWER UKMET/ECMWF SOLUTIONS OF MORE WIDESPREAD PRECIP ON SUNDAY
COULD OCCUR. THIS LOWERS FORECAST CONFIDENCE IN POP FORECAST FOR
SUNDAY. RAINFALL TOTALS ON SUNDAY ARE EXPECTED TO BE UP TO ONE-TENTH
INCH...WITH NEAR ZERO MUCAPES KEEPING THUNDER CHANCES NEAR ZERO.
CLOUD COVERAGE WILL KEEP SUNDAY HIGH TEMPS RANGING FROM THE UPPER
50S NORTHEAST TO MID 60S SOUTHWEST. HOWEVER...THESE TEMPS ARE A FEW
DEGREES ABOVE MAV GUIDANCE WHICH IS ON THE COOL SIDE WHEN COMPARED TO
ENSEMBLE MOS GUIDANCE GIVEN ENDING PRECIP PARTICULARLY OVER SOUTHERN
AND WESTERN AREAS. WINDS WILL BECOME MORE WESTERLY TO NORTHWESTERLY
WHILE DECREASING ON SUNDAY...AS THE SURFACE PRESSURE GRADIENT
RELAXES WEST OF THE DEPARTING AND FILLING LOW PRESSURE SYSTEM. MOST
OF THE RAIN IS EXPECTED TO HAVE ENDED BY SUNDAY AFTERNOON...THOUGH
AN ISOLATED SHOWER COULD LINGER OVER EASTERN MISSISSIPPI INTO THE
EVENING. DRY CONDITIONS IN THE VICINITY OF A SURFACE HIGH BUILDING
OVER THE REGION WILL MAINTAIN DRY CONDITIONS FOR SUNDAY NIGHT INTO
MONDAY NIGHT.
FOR MID- TO LATE-WEEK...A SERIES OF SHORTWAVE TROUGHS AND ASSOCIATED
SURFACE COLD FRONTS WILL DIVE SOUTHEASTWARD ACROSS THE MIDWEST AND
OHIO VALLEY REGIONS...CARVING OUT A MEAN TROUGH OVER THE EASTERN
CONUS. NWP MODEL GUIDANCE HAS COME INTO BETTER AGREEMENT IN DROPPING
ONE OF THESE COLD FRONTS SOUTHWARD ACROSS THE REGION ON TUESDAY. THE
FRONT WILL BECOME MORE SHALLOW AS IT APPROACHES AND MOVES ACROSS THE
ARKLAMISS AS THE ASSOCIATED UPPER TROUGH AND STRONGER DEEP-LAYER
SYNOPTIC-SCALE ASCENT REMAIN WELL NORTH OF THE AREA. NEVERTHELESS...
MOISTURE POOLING ALONG THE BOUNDARY RESULTING IN PWATS NEAR ONE INCH
WILL BE SUFFICIENT FOR ISOLATED LIGHT SHOWERS ALONG OR JUST BEHIND
THE SURFACE FRONT...ALONG WITH AN INCREASE IN CLOUDS. POPS WERE
LOWERED FROM MEX GUIDANCE TO SLIGHT CHANCE FOR LATE MONDAY NIGHT
OVER NORTHWESTERN AREAS...AS THE OPERATIONAL GFS APPEARS TO MOVE THE
FRONT TOO QUICKLY TO THE SOUTH RELATIVE TO GFS ENSEMBLE MEMBERS AND
ECMWF...AND WITH WEAK UPPER SUPPORT OVER THE ARKLAMISS. BEHIND THE
FRONT...WINDS WILL BECOME NORTHERLY AND ADVECT COOLER AIR ACROSS THE
REGION...WITH HIGH PRESSURE BUILDING IN THE WAKE OF THE FRONT.
FOR WEDNESDAY NIGHT OR THURSDAY...A REINFORCING COLD FRONT WILL
QUICKLY SURGE SOUTH ACROSS THE REGION...THOUGH DEEP-LAYER DRY AIR
WILL BE IN PLACE /PWATS OF ONLY 0.3 INCHES/ PRECLUDING PRECIP CHANCES
WITH THIS FRONT. THE ONLY IMPACTS TO SENSIBLE WEATHER WITH THE FRONT
WILL BE AN INCREASE IN NORTH WINDS ALONG WITH THE POTENTIAL FOR MUCH
COOLER CONDITIONS LATE IN THE WEEK. THE CORE OF THE COLD AIRMASS
WILL REMAIN NORTH OF THE CWA...THOUGH GFS AND ECMWF INDICATE 850-MB
TEMPS FALLING TO 3C ACROSS NORTHERN AREAS BEHIND THE FRONT...
POTENTIALLY SUPPORTING TEMPERATURES SEVERAL DEGREES BELOW SEASONAL
AVERAGES. HOWEVER...SIGNIFICANT DIFFERENCES BETWEEN GFS AND ECMWF IN
THE CHARACTERISTICS OF THE ASSOCIATED UPPER TROUGH SUGGEST LOW
CONFIDENCE IN THE TIMING OF THE CORRESPONDING SURFACE FRONT...AS
WELL AS HOW COLD TEMPERATURES GET. /COHEN/
&&
.AVIATION...A LOW PRESSURE SYSTEM APPROACHING FROM THE WEST IS
SENDING A CIRRUS SHIELD INTO THE AREA TODAY. THIS CLOUD DECK WILL
GRADUALLY LOWER TONIGHT...BUT CEILINGS SHOULD REMAIN ABOVE 8000 FT
THROUGH THE NIGHT GIVEN THE VERY DRY LOW LEVEL AIR IN PLACE. AS RAIN
DEVELOPS OVER THE AREA NORTH OF A WARM FRONT...CEILINGS AND
VISIBILITY WILL DETERIORATE...ESPECIALLY AT HBG/MEI WHERE IFR
CEILINGS MAY BECOME PREVALENT PRIOR TO NOON SATURDAY. ALL SITES
COULD EXPERIENCE MVFR/IFR RESTRICTIONS DUE TO LOWER CEILINGS AND
RAIN AS WE GO INTO SATURDAY AFTN/NIGHT. GREATER INSTABILITY IN THE
HBG AREA WILL SUPPORT A FEW TSTMS FROM LATE SAT MORNING INTO SAT
AFTN. /EC/
&&
.PRELIMINARY POINT TEMPS/POPS...
JACKSON 63 47 58 48 / 4 61 87 64
MERIDIAN 64 45 59 47 / 1 38 86 63
VICKSBURG 62 47 56 47 / 7 68 88 58
HATTIESBURG 65 48 59 49 / 7 49 79 55
NATCHEZ 62 47 56 45 / 18 80 82 45
GREENVILLE 62 46 56 47 / 4 34 80 69
GREENWOOD 64 45 55 48 / 2 24 83 80
&&
.JAN WATCHES/WARNINGS/ADVISORIES...
MS...NONE.
LA...NONE.
AR...NONE.
&&
$$
BK/EC
000
FXUS64 KJAN 201100
AFDJAN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON MS
500 AM CST FRI NOV 20 2009
.DISCUSSION...
TODAY THROUGH SATURDAY NIGHT...
AREAS OF FROST THIS MORNING WILL BE THE LAST FOR A WHILE AS THE
EFFECTS OF THE NEXT RAIN MAKER BEGIN TO TAKE SHAPE OVER THE AREA.
WEAK ASCENT WILL DEVELOP IN WEAK WAVES THAT TRAVEL INTO THE REGION
IN SWLY FLOW ALOFT TODAY...RESULTING IN MID/HIGH CLOUDS LIFTING INTO
THE ARKLAMISS. SURFACE HIGH PRESSURE WILL CONTINUE TO LIFT OUT TO
OUR NE WHILE A SURFACE LOW UPSTREAM TRACKS INTO THE WRN GULF.
LOCATIONS IN THE FAR SW CORNER OF THE REGION WILL SEE A SLIGHT
CHANCE OF LIGHT RAIN LATE IN THE AFTERNOON BEFORE RAIN CHANCES
INCREASE TONIGHT.
THE UPPER LOW WILL PIVOT INTO ERN TX TONIGHT. THE ASSOCIATED SURFACE
LOW WILL TRACK TO THE EAST ACROSS THE NRN GULF WITH DIFFERING
SOLUTIONS FROM EACH MODEL REGARDING ITS EVENTUAL EVOLUTION. THE
FORECAST WILL BE A BIT TRICKY FOR THIS FEATURE WITH DISCREPANCIES
NOTED BETWEEN THE MODELS AND IN SOME CASES RUN TO RUN DISCREPANCIES
WITHIN A SINGLE MODEL. GENERALLY FOLLOWED GFS MOS POPS FOR THE
SHORT TERM...CUTTING POPS A BIT FROM THE NE FOR TONIGHT AND
INCREASING POPS SLIGHTLY FOR THE SE SATURDAY NIGHT. ALTHOUGH MODEL
DISCREPANCIES EXIST REGARDING THE EXACT POSITION OF FEATURES IN THE
SHORT TERM...THEY GENERALLY AGREE THAT PRECIP IS LIKELY FOR THE
REGION IN THE SHORT TERM. CONSIDERING BOTH THE SLOWER MODEL
SOLUTIONS AND THE NEWD TRACK OF THE SURFACE LOW WITH THE FASTER
MODELS...THE FORECAST WILL MAINTAIN GOOD RAIN CHANCES INTO SATURDAY
NIGHT PER GFS MOS NUMBERS FOR THE AREA.
BROAD ASCENT WILL INCREASE SATURDAY AS THE UPPER TROUGH APPROACHES.
HAVE ADDED TSTMS TO THE FORECAST FOR SATURDAY AND SATURDAY NIGHT AS
BOTH THE GFS AND EURO INDICATE ELEVATED INSTABILITY OVER THE AREA.
LOW LEVEL HELICITY AND DEEP LAYER SHEAR FIELDS ARE FORECAST TO
INTENSIFY FOR SATURDAY...INTRODUCING THE POSSIBILITY OF A FEW STRONG
THUNDERSTORMS FOR AREAS EAST OF THE NATCHEZ TRACE. GUSTY WIND WILL
ALSO DEVELOP DURING THE DAY SATURDAY AS THE SURFACE LOW TRACKS TO
THE EAST AND THE LOW LEVEL JET INCREASES. WILL NOT MENTION EITHER IN
THE HWO FOR NOW. HOWEVER A LAKE WIND ADVISORY MAY BE REQUIRED FOR
SATURDAY DEPENDING ON THE TRACK OF THE SURFACE LOW.
SUNDAY THROUGH FRIDAY...
BY 1200 UTC SUNDAY...LARGE SPREAD EXISTS AMONGST NWP MODEL GUIDANCE
WITH REGARD TO THE POSITION OF THE SURFACE LOW...AROUND 1009 MB.
MOST PERTURBATIONS OF THE GFS ENSEMBLE...AS WELL AS THE OPERATIONAL
GFS...CLUSTER THE LOW AROUND CENTRAL OR SOUTHERN ALABAMA AT THIS
TIME...CONSISTENT WITH THE NAM. THESE MODELS INDICATE MOISTURE
WRAPPING AROUND THE LOW...WITH THE OPERATIONAL GFS SHOWING A SUBTLE
SURFACE CONFLUENCE AXIS EXTENDING WEST OF THE SURFACE LOW. LOW LEVEL
CONVERGENCE NEAR THESE FEATURES WOULD SUPPORT RAIN CONTINUING OVER
THE NORTHEASTERN CWA ON SATURDAY...WHILE DRIER AIR WRAPPING INTO THE
SOUTHERN SEMICIRCLE OF THE LOW WOULD REDUCE PRECIP CHANCES
ELSEWHERE. THE UKMET AND ECMWF ARE AT THE SOUTHERN AND WESTERN
EXTENT OF THE GUIDANCE ENVELOPE WITH REGARD TO THE POSITION OF THE
SURFACE LOW...KEEPING HIGHER PRECIP CHANCES ACROSS MUCH OF THE AREA
THROUGH THE DAY. GIVEN CONTRACTING WAVELENGTH OF SUPPORTING UPPER
TROUGH...THE MORE PROGRESSIVE GFS/NAM SOLUTION IS PREFERRED...AND
MAV POPS WERE FOLLOWED FOR SUNDAY. HOWEVER...SHOULD THE UPPER LOW
DISCONNECT SOME FROM THE SOUTHERN STREAM AND SLOW DOWN...THEN THE
SLOWER UKMET/ECMWF SOLUTIONS OF MORE WIDESPREAD PRECIP ON SUNDAY
COULD OCCUR. THIS LOWERS FORECAST CONFIDENCE IN POP FORECAST FOR
SUNDAY. RAINFALL TOTALS ON SUNDAY ARE EXPECTED TO BE UP TO ONE-TENTH
INCH...WITH NEAR ZERO MUCAPES KEEPING THUNDER CHANCES NEAR ZERO.
CLOUD COVERAGE WILL KEEP SUNDAY HIGH TEMPS RANGING FROM THE UPPER
50S NORTHEAST TO MID 60S SOUTHWEST. HOWEVER...THESE TEMPS ARE A FEW
DEGREES ABOVE MAV GUIDANCE WHICH IS ON THE COOL SIDE WHEN COMPARED TO
ENSEMBLE MOS GUIDANCE GIVEN ENDING PRECIP PARTICULARLY OVER SOUTHERN
AND WESTERN AREAS. WINDS WILL BECOME MORE WESTERLY TO NORTHWESTERLY
WHILE DECREASING ON SUNDAY...AS THE SURFACE PRESSURE GRADIENT
RELAXES WEST OF THE DEPARTING AND FILLING LOW PRESSURE SYSTEM. MOST
OF THE RAIN IS EXPECTED TO HAVE ENDED BY SUNDAY AFTERNOON...THOUGH
AN ISOLATED SHOWER COULD LINGER OVER EASTERN MISSISSIPPI INTO THE
EVENING. DRY CONDITIONS IN THE VICINITY OF A SURFACE HIGH BUILDING
OVER THE REGION WILL MAINTAIN DRY CONDITIONS FOR SUNDAY NIGHT INTO
MONDAY NIGHT.
FOR MID- TO LATE-WEEK...A SERIES OF SHORTWAVE TROUGHS AND ASSOCIATED
SURFACE COLD FRONTS WILL DIVE SOUTHEASTWARD ACROSS THE MIDWEST AND
OHIO VALLEY REGIONS...CARVING OUT A MEAN TROUGH OVER THE EASTERN
CONUS. NWP MODEL GUIDANCE HAS COME INTO BETTER AGREEMENT IN DROPPING
ONE OF THESE COLD FRONTS SOUTHWARD ACROSS THE REGION ON TUESDAY. THE
FRONT WILL BECOME MORE SHALLOW AS IT APPROACHES AND MOVES ACROSS THE
ARKLAMISS AS THE ASSOCIATED UPPER TROUGH AND STRONGER DEEP-LAYER
SYNOPTIC-SCALE ASCENT REMAIN WELL NORTH OF THE AREA. NEVERTHELESS...
MOISTURE POOLING ALONG THE BOUNDARY RESULTING IN PWATS NEAR ONE INCH
WILL BE SUFFICIENT FOR ISOLATED LIGHT SHOWERS ALONG OR JUST BEHIND
THE SURFACE FRONT...ALONG WITH AN INCREASE IN CLOUDS. POPS WERE
LOWERED FROM MEX GUIDANCE TO SLIGHT CHANCE FOR LATE MONDAY NIGHT
OVER NORTHWESTERN AREAS...AS THE OPERATIONAL GFS APPEARS TO MOVE THE
FRONT TOO QUICKLY TO THE SOUTH RELATIVE TO GFS ENSEMBLE MEMBERS AND
ECMWF...AND WITH WEAK UPPER SUPPORT OVER THE ARKLAMISS. BEHIND THE
FRONT...WINDS WILL BECOME NORTHERLY AND ADVECT COOLER AIR ACROSS THE
REGION...WITH HIGH PRESSURE BUILDING IN THE WAKE OF THE FRONT.
FOR WEDNESDAY NIGHT OR THURSDAY...A REINFORCING COLD FRONT WILL
QUICKLY SURGE SOUTH ACROSS THE REGION...THOUGH DEEP-LAYER DRY AIR
WILL BE IN PLACE /PWATS OF ONLY 0.3 INCHES/ PRECLUDING PRECIP CHANCES
WITH THIS FRONT. THE ONLY IMPACTS TO SENSIBLE WEATHER WITH THE FRONT
WILL BE AN INCREASE IN NORTH WINDS ALONG WITH THE POTENTIAL FOR MUCH
COOLER CONDITIONS LATE IN THE WEEK. THE CORE OF THE COLD AIRMASS
WILL REMAIN NORTH OF THE CWA...THOUGH GFS AND ECMWF INDICATE 850-MB
TEMPS FALLING TO 3C ACROSS NORTHERN AREAS BEHIND THE FRONT...
POTENTIALLY SUPPORTING TEMPERATURES SEVERAL DEGREES BELOW SEASONAL
AVERAGES. HOWEVER...SIGNIFICANT DIFFERENCES BETWEEN GFS AND ECMWF IN
THE CHARACTERISTICS OF THE ASSOCIATED UPPER TROUGH SUGGEST LOW
CONFIDENCE IN THE TIMING OF THE CORRESPONDING SURFACE FRONT...AS
WELL AS HOW COLD TEMPERATURES GET. /COHEN/
&&
.AVIATION...PATCHES OF DENSE FOG CAN BE EXPECTED UNTIL JUST AFTER
SUNRISE THIS MORNING...LOCALLY LOWERING VSBY TO 1/4 MILE WITH
BKN-OVC CIGS BLO 500 FEET. OTHERWISE...EXPECT OCCASIONAL LIGHT FOG
WITH VSBY ABOVE 4 MILES. SKIES WILL BE CLEAR AT MOST LOCATIONS THIS
MORNING BUT CLOUDS WILL INCREASE FROM THE WEST DURING THE DAY. VFR
CONDITIONS WILL CONTINUE AS CLOUD DECKS REMAIN ABOVE 7-9K FEET THIS
AFTERNOON. RAIN CHANCES WILL INCREASE THIS EVENING AND CLOUDS WILL
INCREASE... BECOMING BKN-OVC 2-4K FEET BY MIDNIGHT. RAIN WILL BE
LIKELY SATURDAY WITH SCT TSTMS...GENERALLY S OF INTERSTATE 20.
&&
.PRELIMINARY POINT TEMPS/POPS...
JACKSON 62 47 58 48 / 4 61 87 64
MERIDIAN 64 45 59 47 / 1 38 86 63
VICKSBURG 62 47 56 47 / 7 68 88 58
HATTIESBURG 65 48 59 49 / 7 49 79 55
NATCHEZ 60 47 56 45 / 18 80 82 45
GREENVILLE 61 46 56 47 / 4 34 80 69
GREENWOOD 64 45 55 48 / 2 24 83 80
&&
.JAN WATCHES/WARNINGS/ADVISORIES...
MS...NONE.
LA...NONE.
AR...NONE.
&&
$$
03/COHEN
000
FXUS64 KJAN 200236 AAA
AFDJAN
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE JACKSON MS
835 PM CST THU NOV 19 2009
.UPDATE...LATEST SATELLITE IMAGERY SHOWS SOME MID TO UPPER LEVEL MOISTURE
MOVING TOWARD THE REGION AHEAD OF A SHORT WAVE IN THE SOUTHERN
PLAINS. SO HAVE MADE SLIGHT ADJUSTMENTS TO THE SKY GRIDS FOR THE MID
TO UPPER LEVEL CLOUDS. EXPECT THE CLOUDS TO BE IN A SCATTERED NATURE
AND NOT HAVE MUCH AFFECT ON OVERNIGHT TEMPS. SO WILL HOLD ON TO COOL
TEMPS. TEMPS HAVE ALREADY DIPPED INTO THE LOWER TO MIDDLE 40S AS OF
8 PM. SO WILL KEEP CURRENT LOWS FROM THE LOWER 30S EAST TO THE LOWER 40S
WEST. THE REST OF FORECAST APPEARS TO BE ON TRACK. /17/
./PREV DISCUSSION...319 PM CST THU NOV 19 2009
.SHORT TERM...TONIGHT THROUGH SATURDAY NIGHT...ANOTHER CHILLY NIGHT
TONIGHT AS SURFACE RIDGE OF HIGH PRESSURE COUPLES WITH DRY WESTERLY
FLOW ALOFT TO ALLOW EFFICIENT RADIATIONAL COOLING THROUGH THE EARLY
MORNING HOURS. MORNING LOWS WILL BE CLOSE TO THIS MORNING ALTHOUGH
NOT QUITE AS COLD AS THE HIGH CENTER SHIFTS FURTHER TO THE NE. STILL
EXPECTING TEMPS TO DROP INTO THE MID TO LOWER 30S ACROSS NORTHEASTERN
AREAS ALLOWING PATCHY FROST TO DEVELOP.
FRIDAY WILL BE ANOTHER NICE DAY AS THE ARKLAMISS IS IN TRANSITION
WITH HIGH PRESSURE RETREATING TO THE NORTHEAST AND A S/WV CROSSING
THE RIO GRANDE VALLEY APPROACHING FROM THE WEST. UPPER LEVEL CLOUDS
WILL BE ON THE INCREASE DURING THE DAY BUT TEMPS WILL STILL WARM
NICELY INTO THE MID 60S. RAIN CHANCES WILL INCREASE LATE FRIDAY
NIGHT AS THE S/WV DEVELOPS A CLOSED SURFACE CIRCULATION OVER THE
WESTERN GULF OF MEXICO AND DRAGS IT TO THE NORTHEAST TOWARD OUR CWA.
INCREASING CLOUD COVER WILL KEEP LOW TEMPS SAT MORNING MUCH WARMER
WITH LOWS BOTTOMING OUT IN THE MID TO LOW 40S NORTHEAST TO UPPER 40S
SOUTH. PRECIP COVERAGE WILL CONTINUE INCREASING THROUGH THE DAY
SATURDAY AS THE LOW CENTER TRACKS OVER SOUTHEASTERN LA AND INTO THE
ARKLAMISS SATURDAY NIGHT. RAIN CHANCES SHOULD BEGIN TO DIMINISH FROM
SOUTHWEST TO NORTHEAST EARLY SUNDAY MORNING AS SUBSIDENT NW FLOW IN
WAKE OF THE TROUGH MOVES INTO THESE AREAS.
RAIN TOTALS COME SUNDAY MORNING AREN`T TOO IMPRESSIVE DUE TO THE
PROGRESSIVE NATURE OF THE SYSTEM...COUPLED WITH PEAK PW VALUES
NEAR 1.25 IN. AS A RESULT...THREE QUARTERS OF AN INCH ACROSS MOST
AREAS CAN BE EXPECTED WITH LOCALIZED AREAS IN THE SOUTHEAST POSSIBLY
SEEING AS MUCH AS 1.25 IN. TOTALS THIS HIGH WILL BE VERY LIMITED IN
NATURE. EASTERLY WINDS WILL DEFINITELY BE ON THE INCREASE SAT
AFTERNOON AS THE SFC LOW APPROACHES WITH GUSTS TO 20 MPH POSSIBLE
ACROSS AREAS ALONG AND SOUTH OF THE HWY 84 CORRIDOR. WIDESPREAD GUSTY
WX CAN BE EXPECTED LATE SAT INTO SUN MORNING AND WILL LIKELY NEED A
LAKE WIND ADVISORY DURING THIS TIME.
THE DEVELOPMENT AND TRACK OF THE LOW ARE HANDLED SIMILARLY BY THE
MODELS ALTHOUGH THE GFS IS ON THE FASTER/STRONGER EDGE OF THE
GUIDANCE ENVELOPE. ENSEMBLE SOLUTIONS WERE MORE IN LINE WITH THE 00Z
ECMWF AND I PLACED MORE EMPHASIS ON IT WITH THIS PACKAGE. OVERALL
MAV NUMBERS LOOKED REASONABLE HOWEVER DID INCREASE MOST HIGHS A
DEGREE OR TWO FRIDAY AS GFS APPEARS A BIT ROBUST IN ITS CLOUD COVER
MOVING ACROSS MS AT THIS TIME. SUNDAYS LOW WERE DEFINITELY ON THE
HIGH SIDE OF THE GUIDANCE AND KNOCKED ALL AREAS DOWN A BIT. /BK/
.PREVIOUS LONG TERM...SURFACE HIGH PRESSURE BUILDS INTO THE
REGION SUNDAY...BRINGING DRY CONDITIONS FOR SUNDAY AFTERNOON INTO
EARLY NEXT WEEK.
BEGINNING TUESDAY...NWP MODEL GUIDANCE BEGINS TO DIVERGE SOMEWHAT.
OPERATIONAL GFS AND GFS ENSEMBLE MEMBERS INDICATE A MEAN TROUGH OVER
THE EASTERN CONUS FOR TUESDAY THROUGH THURSDAY...WITH WEAKLY
SUBSIDENT WEST-TO-NORTHWEST MID/UPPER-LEVEL FLOW PROVIDING DRY
CONDITIONS FOR MID-WEEK. THE OPERATIONAL GFS INDICATES A SHORTWAVE
TROUGH DIVING SOUTHEASTWARD OVER THE MIDWEST ON TUESDAY WHILE
AMPLIFYING AND DEEPENING THROUGH THURSDAY AS A CLOSED LOW DEVELOPS
OVER THE GREAT LAKES REGION. AN ASSOCIATED COLD FRONT IS FORECAST TO
PUSH SOUTHWARD ACROSS THE AREA ON TUESDAY...FOLLOWED BY COOLER AND
MORE DRY CONDITIONS...ALONG WITH AN INCREASE IN NORTHERLY WINDS. THE
OPERATIONAL GFS AND ECMWF ALSO SHOW A SECONDARY COLD FRONT PUSHING
SOUTH ACROSS THE AREA ON WEDNESDAY NIGHT OR THURSDAY. WHILE LARGE
SPREAD EXISTS IN THE EXACT DETAILS OF THE MID/UPPER-LEVEL TROUGHS AND
ASSOCIATED SURFACE FRONTS...CONSENSUS IS THAT THE REGION WILL
EXPERIENCE GENERALLY DRY CONDITIONS...WITH ONE OR MORE FRONTAL SURGES
FOR MID-WEEK. WHILE A COUPLE MEMBERS OF THE GFS ENSEMBLE AND THE
ECMWF INDICATE A SMALL CHANCE FOR SHOWERS ACCOMPANYING THE
FRONTS...MOST GUIDANCE INDICATES DRY CONDITIONS...AND THUS FORECAST
POPS ARE BEING KEPT BELOW SLIGHT CHANCE CATEGORY. AS FOR
TEMPERATURES...HIGH TEMPERATURES FOR MID-WEEK WERE LOWERED A FEW
DEGREES BELOW MAV GUIDANCE...CONSISTENT WITH CONSENSUS AMONG GFS
ENSEMBLES ALONG WITH POST-FRONTAL COLD AIR ADVECTION REGIMES FOR
TUESDAY AND THURSDAY. /COHEN/
&&
.AVIATION...VFR CONDITIONS ARE BEING REPORTED THIS EVENING AT ALL
TAF SITES WITH ONLY A SOME HIGH CLOUDS NOTED ON SATELLITE IMAGERY
MOVING ACROSS THE REGION. HOWEVER SATELLITE IMAGERY ALSO SHOWS SOME
LOWER CLOUDS AROUND 6KFT MOVING EAST TOWARD THE REGION. EXPECT SOME
SCATTERED TO BROKEN MID TO UPPER LEVEL CLOUDS TO MOVE OVER THE REGION
DURING THE NIGHT. THE MID LEVEL CLOUDS WILL AFFECT AREAS MAINLY ALONG
AND WEST OF THE MISSISSIPPI RIVER. HIGH PRESSURE CENTERED OVER
WESTERN ALABAMA WILL REMAIN IN CONTROL OF OUR AREA WHILE IT MOVES
SLOWLY TO THE NORTHEAST TONIGHT. THIS WILL RESULT IN MORE OF AN
EASTERLY COMPONENT TO OUR WIND ALTHOUGH MOST ASOS SITES WILL REPORT
CALM WINDS TONIGHT. THE DRY EAST WIND SHOULD HINDER FOG DEVELOPMENT
AND WILL NOT INCLUDE MENTION IN TAFS. THUS...VFR CONDITIONS SHOULD
PREVAIL THROUGH TONIGHT AND INTO FRIDAY. EXPECT BROKEN MID TO UPPER
CLOUDS TO INCREASE ACROSS THE REGION ON FRIDAY AHEAD OF THE NEXT SYSTEM.
LOWER DECK CLOUDS WILL COME IN WITH THE SHOWERS FOR FRIDAY NIGHT
INTO SATURDAY./17/
&&
.PRELIMINARY POINT TEMPS/POPS...
JACKSON 39 66 46 60 / 0 0 34 73
MERIDIAN 34 67 42 62 / 0 0 21 73
VICKSBURG 40 66 44 60 / 0 0 38 76
HATTIESBURG 39 67 47 62 / 0 2 34 76
NATCHEZ 42 67 47 58 / 0 2 67 80
GREENVILLE 40 65 45 62 / 0 0 21 66
GREENWOOD 38 67 45 63 / 0 0 19 66
&&
.JAN WATCHES/WARNINGS/ADVISORIES...
MS...NONE.
LA...NONE.
AR...NONE.
&&
$$
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