National Weather Service United States Department of Commerce

 


000
FXUS62 KILM 221126
AFDILM

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON NC
626 AM EST SUN DEC 22 2014

.SYNOPSIS...
MOISTURE WILL OVERRUN A COOL SURFACE AIRMASS TODAY LEADING TO
PERIODS OF LIGHT RAIN. THIS AIRMASS LIFTS OUT ON TUESDAY CLEARING
THE PATH FOR WARMER TEMPERATURES AND EVEN MORE MOISTURE. A COLD FRONT
MAY ADD SOME THUNDER WEDNESDAY AND WEDNEDAY NIGHT. DRY AND
SEASONABLE WEATHER RETURNS FOR CHRISTMAS AND THE DAYS THAT FOLLOW.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 630 AM MONDAY...SURFACE LOW PRESSURE IS MOVING NE ALONG A
FRONT STALLED ABOUT 40 MILES SOUTHEAST OF CAPE FEAR. 00Z MODELS
SHOWED A SURPRISING DEGREE OF SPREAD IN HOW THEY HANDLE THE
FRONT...BUT FORTUNATELY MY FORECAST DECISION LOOKS EASY: THE 00Z GFS
WAS HORRIBLE EVEN IN ITS INITIALIZATION AND IS BEING AVOIDED. THIS
FORECAST IS BASED ON THE 00Z NAM WHICH INITIALIZED WELL AND LOOKS
REALISTIC IN ITS MAINTENANCE OF THE COOL WEDGE AIRMASS THROUGH THE
DAY. UPDATE FOR 06Z MODELS: THE 06Z GFS WAS A LITTLE BETTER THAN THE
00Z VERSION BUT STILL TOO FAR WEST WITH THE COASTAL FRONT. THE NAM
CONTINUES TO BE THE PREFERRED MODEL.

WARM ADVECTION AND LIFT ON THE 295K-300K ISENTROPIC SURFACES BOTH
TAPER OFF AROUND SUNRISE. PLENTY OF LOW-LEVEL MOISTURE SHOULD
CONTINUE...BUT WITH LITTLE IF ANY SYNOPTIC LIFT IS EXPECTED DURING
THE DAY. THIS SHOULD MAINTAIN DENSE LOW CLOUDS AND MAYBE SOME PATCHY
DRIZZLE. INTERESTINGLY WITH MARGINALLY UNSTABLE CONDITIONS ALOFT
ROOTED IN THE 875-850 MB LAYER THERE ARE SEVERAL CLUSTER OF SHOWERS
AND EVEN ISOLATED THUNDERSTORMS FIRING ACROSS THE AREA. I HAVE ADDED
HIGHER POPS THROUGH THE MORNING HOURS TO ACCOUNT FOR THIS CONVECTIVE
ACTIVITY WHICH WAS NOT ANTICIPATED EARLIER ON THE MIDNIGHT
SHIFT.

WITH SUN ANGLES AS LOW AS THEY GET AND A CLASSIC WEDGE PATTERN...
LOOK FOR TEMPERATURES TO HARDLY BUDGE TODAY: HIGHS SHOULD RANGE FROM
42-46 INLAND TO 47-50 AT THE BEACHES.

LOW CLOUDS CONTINUE TONIGHT. ISENTROPIC LIFT MAY INCREASE AFTER
MIDNIGHT...ESPECIALLY ACROSS INTERIOR AREAS WHERE COLD AIR DEPTH AND
FRONTAL SLOPE WILL BE GREATEST. THEREFORE I HAVE POPS RAMPING
BACK UP TOWARD 40 PERCENT LATE. THE COASTAL FRONT MAY ALSO BEGIN TO
MOVE WESTWARD LATE AS HIGH PRESSURE RETREATS OUT OF NEW ENGLAND AND
SURFACE PRESSURES FALL ACROSS THE CAROLINA AND MID-ATLANTIC
PIEDMONT REGION. THE COASTAL FRONT MAY ACTUALLY APPROACH GEORGETOWN
BY DAYBREAK TUESDAY. THIS COULD CREATE AN INTERESTING HOURLY
TEMPERATURE PROFILE WITH LOWS OCCURRING IN THE EVENING AND
TEMPERATURES RISING LATE.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
AS OF 3 AM MONDAY...VERY ACTIVE WEATHER EXPECTED FOR THE DURATION OF
THE PERIOD. WEDGE WILL FINALLY BE BREAKING DOWN ON TUESDAY. THE
SPEED AT WHICH THIS OCCURS, WHICH IS NOTORIOUSLY DIFFICULT TO MODEL,
WILL MODULATE HIGH TEMPS. CURRENT FCST LEANS MORE ON THE SLOWER WRF
KEEPING MID 50S INLAND WHILE COASTAL LOCALES GET INTO MID/UPPER 60S.
DEEP SWRLY FLOW OF MOISTURE TO BRING PLENTY OF CLOUDS AND OCCASIONAL
RAIN FROM TIME TO TIME. PINNING DOWN WHERE RAIN WILL BE HEAVIEST IS
DIFFICULT AT THIS TIME. RAINFALL RATES TO INCREASE TUESDAY NIGHT
INTO WEDNESDAY AS STRONGER FLOW AND DYNAMICS SPREAD ACROSS THE
REGION WHILE COLD FRONT APPROACHES FROM THE NORTH AND WEST. THE
STRONGER RESULTING FLOW WILL BRING EVEN MILDER AIR INTO THE COASTAL
PLAIN AND HIGHS IN THE 70S APPEAR LIKELY DESPITE THE CLOUDS AND
RAIN. DESPITE THE WARMTH FORECAST SOUNDINGS SHOW SUCH POOR LAPSE
RATES THAT INSTABILITY IS REALLY GOING TO BE TOUGH TO COME BY, MAYBE
ENOUGH ENOUGH TO WORRY ABOUT HSLC SETUP. HAVE LEFT ISO THUNDER AS
SOME FAIRLY STRONG VERTICAL MOTION MAY IMPACT THE REGION LATE IN THE
PERIOD. WEDNESDAY NIGHT`S LOWS MAY BE VERY MILD LIKE TUESDAY NIGHT
SAVE FOR SOME COLD ADVECTION RELATED TO FROPA TOWARDS DAYBREAK
THURSDAY. SIMILARLY RAIN WILL BE RAPIDLY SHUTTING OFF FROM WEST TO
EAST LATE WEDNEDAY NIGHT...THE EXACT TIMING LIKELY NEEDING OF SOME
REFINEMENT IN FUTURE FORECASTS.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
AS OF 3 AM MONDAY...CHRISTMAS AND THE FEW DAYS THAT FOLLOW WILL
FEATURE A RETURN OF SUNSHINE...NOT SEEN IN QUITE A WHILE. ALSO SINCE
THE UPPER WAVE DRIVING THE FRONT THROUGH NOW RETAINS A DEFINED
POSITIVE TILT THE COLD ADVECTION APPEARS QUITE TEMPERED AND THE
HOLIDAY WEEKEND NO LONGER SEEMS TO OFFER UP UNSEASONABLY COOL
TEMPERATURES IN FAVOR OF SEASONABLE WEATHER IF NOT A FEW DEGREES
ABOVE. MOISTURE MAY BE ON THE RISE BY SUNDAY AS A WEAK COLD FRONT
APPROACHES IN A STILL RATHER LOW AMPLITUDE PATTERN ALOFT.

&&

.AVIATION /12Z MONDAY THROUGH FRIDAY/...
AS OF 12Z...LIFR CIGS/MVFR VSBYS AT THE COASTAL TERMINALS THIS
MORNING WHILE INLAND TERMINALS HAVE IFR CIGS/VFR VSBYS. OCCASIONALLY
VSBYS DROP A CATEGORY OR TWO LOWER AS LIGHT RAIN...WITH ISOLATED
EMBEDDED CONVECTIVE SHOWERS/THUNDERSTORMS MOVE NE ACROSS THE AREA.

CIGS LESS THAN 600-700 FEET AND VSBYS 3-5SM WILL BE LIKELY THIS
MORNING. THE BULK OF THE SHOWERS/ISOLATED THUNDERSTORMS PER RADAR
LOOPS WILL MOVE BETWEEN THE INLAND AND COASTAL TERMINALS THIS
MORNING SO WILL NOT INDICATE VCTS IN TAFS. VSBYS COULD DROP TO 1-3SM
IN LIGHT SHOWERS/BR ESPECIALLY AT THE COASTAL TERMINALS. CIGS SHOULD
LIFT ABOVE 600-700 FEET WITH VSBYS 6SM+ BY LATE MORNING/EARLY
AFTERNOON. CIGS FLIRT AROUND 1K LATER THIS AFTERNOON BUT CONFIDENCE
IS NOT HIGH. EVEN IF CIGS RISE CIGS WILL DROP AGAIN AOB 600-700 FEET
BY MIDNIGHT Z.

EXTENDED OUTLOOK...LIFR/IFR CIGS TUE WITH INCREASING CHANCES OF
SHOWERS. MVFR COASTAL TERMINALS LATER IN THE DAY. WED EXPECT
SHOWERS/MVFR AND GUSTY WINDS AHEAD OF A COLD FRONT. GUSTY WEST WINDS
AND VFR THU BEHIND THE FRONT. VFR ON FRI.

&&

.MARINE...
NEAR TERM /THROUGH TONIGHT/...
AS OF 630 AM MONDAY...A COASTAL FRONT IS STALLED ABOUT 40 MILES
SOUTHEAST OF CAPE FEAR. LOW PRESSURE IS MOVING NE ALONG THE FRONT
AND SHOULD BE NORTH OF CAPE FEAR BY MID-MORNING. THIS WILL TAKE THE
PERIOD OF STRONGEST OF NE WINDS NORTH OF THE AREA...REPLACED WITH A
LIGHTER NORTHERLY WIND THAT SHOULD LAST INTO TONIGHT. THE SMALL
CRAFT ADVISORY HAS EXPIRED FOR THE SC WATERS...HOWEVER IT WILL
REMAIN IN EFFECT THROUGH 9 AM FOR THE NC WATERS...MAINLY TO ALLOW
SEAS TIME TO SUBSIDE BELOW 6 FEET. THE FRYING PAN SHOALS BUOY IS
STILL REPORTING 6.6 FOOT SEAS AT LAST REPORT.

SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
AS OF 3 AM MONDAY...TUESDAY CHARACTERIZED BY WEAKENING WEDGE OF HIGH
PRESSURE OVER LAND. THE SPEED AT WHICH THIS OCCURS IS ALWAYS A BIT
UNCERTAIN AND THIS WILL AFFECT HOW QUICKLY LOCAL WINDS VEER AND
INCREASE IN SPEED. HAVE OPTED FOR THE SLOWER MODEL SOLUTION WHICH
WILL KEEP THE MAIN DETERIORATION OF CONDITIONS OFF UNTIL TUESDAY
NIGHT. AT THIS TIME THE SSWRLY FLOW REALLY BECOMES ESTABLISHED IN A
STRENGTHENING STATE AS LOW LEVEL WIND FIELDS CRANK UP AND A COLD
FRONT AND STRONG UPPER TROUGH APPROACH. SMALL CRAFT ADVISORY
EXPECTED BY TUES NIGHT. WIND AND SEAS ONLY INCREASE FROM THERE AS
THE APPROACHING BOUNDARY TIGHTENS THE GRADIENT AND THE APPROACH OF
THE UPPER WAVE STRENGTHENS LOW LEVEL WIND FIELDS. FROPA EXPECTED
TOWARDS THE END OF THE PERIOD WITH AN ABRUPT WIND VEER.

LONG TERM /THURSDAY THROUGH FRIDAY/...
AS OF 3 AM MONDAY...THE LONG TERM STARTS OFF WITH SMALL CRAFT
ADVISORY FLAGS FLYING JUST FOLLOWING VIGOROUSLY DRIVEN COLD FRONT.
HOWEVER THE COLD SURGE ITSELF IS RATHER UNIMPRESSIVE AND WINDS AND
SEAS SHOULD BOTH DROP OFF RATHER NICELY AS THE DAY WEARS ON. TOUGH
TO RULE OUT A PERIOD OF SCEC THOUGH AS THE SHARP WIND SHIFT COULD
LEAD TO RATHER STEEP WAVE FACES EVEN AS THEIR OVERALL HEIGHT
DECREASES. FRIDAY BRINGS A LIGHT OFFSHORE FLOW AS HIGH PRESSURE
SLOWLY BUILDS IN FROM THE WEST.

&&

.TIDES/COASTAL FLOODING...
AS OF 3 AM MONDAY...TIDAL ANOMALIES ARE RUNNING ABOUT +1.0 FOOT AT
WRIGHTSVILLE BEACH AND MYRTLE BEACH THIS MORNING. NE WINDS ALONG THE
COAST ARE LARGELY RESPONSIBLE FOR THIS SURGE. ASTRONOMICAL TIDAL
RANGES ARE LARGER THAN NORMAL DUE TO THE NEW MOON WHICH IS TODAY.
THIS MORNING`S HIGH TIDE WILL OCCUR AROUND 7:15 AM...AND WITH THE
ADDITION OF THE SURGE MAY APPROACH MINOR FLOOD THRESHOLDS NORTH OF
CAPE FEAR. THE COASTAL FLOOD ADVISORY WILL REMAIN IN EFFECT HERE FOR
POSSIBLE MINOR FLOODING. SOUTH OF CAPE FEAR WINDS SHOULD BE BACKING
MORE NORTHERLY OVER THE NEXT FEW HOURS WHICH WILL REDUCE THE AMOUNT
OF SURGE...AND NO ADVISORIES ARE PLANNED HERE.

&&

.ILM WATCHES/WARNINGS/ADVISORIES...
SC...NONE.
NC...COASTAL FLOOD ADVISORY FROM 6 AM TO 9 AM EST MONDAY FOR NCZ106-
108.

MARINE...SMALL CRAFT ADVISORY UNTIL 9 AM EST MONDAY FOR AMZ250-252.

&&

$$

SYNOPSIS...MBB
NEAR TERM...TRA
SHORT TERM...MBB
LONG TERM...MBB
AVIATION...MRR
TIDES/COASTAL FLOODING...TRA