581
FXUS62 KRAH 161229
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
729 AM EST MON DEC 16 2024
SYNOPSIS
HIGH PRESSURE AND ASSOCIATED COLD AIR DAMMING WILL EXTEND ACROSS THE
PIEDMONT OF THE CAROLINAS, WHILE GRADUALLY WEAKENING, THROUGH
TUESDAY. A SERIES OF COLD FRONTS WILL PROGRESS ACROSS THE REGION
WEDNESDAY NIGHT THROUGH SATURDAY.
NEAR TERM /THROUGH TONIGHT/
AS OF 415 AM MONDAY...
THROUGH TONIGHT: THIS MORNING WILL FEATURE WIDESPREAD VERY LOW
OVERCAST, AREAS OF FOG IN THE COASTAL PLAIN, AND PATCHY DRIZZLE OR
LIGHT RAIN OVER THE NRN PIEDMONT. THE THICKNESS OF THE OVERCAST
LAYER IN THE HEART OF THE NOW HYBRID COLD AIR DAMMING OVER THE
PIEDMONT WAS 3000 FT THICK ON THE 00Z-OBSERVED GSO SOUNDING AND WILL
BE VERY SLOW TO LIFT TODAY, AND UNLIKELY TO COMPLETELY DISPERSE OVER
THE NW PIEDMONT. MEANWHILE, ITS ERN EDGE IN ERN NC WILL BE MUCH
QUICKER TO LIFT AND ERODE FROM SOUTHEAST TO NORTHWEST --WITH AN
ACCOMPANYING NWWD RETREAT OF A WEDGE FRONT-- FROM LATE MORNING
THROUGH THE AFTERNOON. TEMPERATURES WILL CONSEQUENTLY BE SHARPLY
RANGING ONES ACROSS THE WEDGE FRONT IN CNTL NC AGAIN TODAY: AROUND
50 F AT INT TO MID/UPR 60S OVER THE ERN SANDHILLS AND SRN COASTAL
PLAIN.
VERY LIGHT FLOW WILL EXIST OVER THE CAROLINAS AND GA TONIGHT, AS A
PIECE OF THE COLD AIR DAMMING HIGH SEPARATES THERE FROM ITS PARENT,
TRANSITORY ONE THAT WILL MOVE WELL OFFSHORE AND ACROSS THE N.
ATLANTIC. THE ASSOCIATED LIGHT FLOW REGIME AND RESIDUAL CAD
STABILITY/RH WILL FAVOR THE REDEVELOPMENT OF FOG AND VERY LOW
OVERCAST TONIGHT. SOME MAY BE DENSE, ESPECIALLY AWAY FROM THE VA
BORDER COUNTIES WHERE A MID-LEVEL CLOUD BAND AND VIRGA/ISOLATED
SPRINKLES WILL MOVE OVERHEAD LATE. LOW TEMPERATURES TONIGHT WILL BE
MOSTLY MID/UPR 40S.
TUESDAY: HIGH PRESSURE AND THE RESIDUAL CAD AIRMASS WILL REMAIN OVER
THE CAROLINAS AND GA. LOW OVERCAST AND FOG IN THE MORNING WILL LIFT
AND DISPERSE MORE QUICKLY THAN ON MON, THOUGH SLOWEST OVER THE NW NC
PIEDMONT WHERE TEMPERATURES WILL HOLD IN 50S THROUGH NOON, THEN
REACH THE LWR-MID 60S BY MID-LATE AFTERNOON. TEMPERATURES WILL
INCREASE MORE QUICKLY AND INTO THE 60S ELSEWHERE, PEAKING IN THE LWR-
MID 70S OVER SERN NC, INCLUDING IN THE ERN SANDHILLS AND SRN-CNTL
COASTAL PLAIN. CONTINUED LIGHT FLOW AND RESIDUAL EFFECTS OF THE CAD
AIRMASS WILL LIKELY RESULT IN THE REDEVELOPMENT OF AREAS OF FOG BY
MID-EVENING, WITH SOME POSSIBLY AGAIN DENSE OVERNIGHT.
SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/
AS OF 305 AM MONDAY...
BY TUESDAY NIGHT, LOW PRESSURE WILL BE ACROSS FAR EASTERN CANADA
WITH A COLD FRONT EXTENDING SOUTH INTO THE WESTERN ATLANTIC THEN
BACK TO THE SOUTHWEST ACROSS VIRGINIA AND TENNESSEE. ANOTHER WAVE OF
LOW PRESSURE WILL DEVELOP ALONG THE FRONT AND MOVE NORTHEAST. THE
ECMWF/EPS HAS REMAINED VERY CONSISTENT OVER THE LAST THREE DAYS
DEVELOPING THE SYSTEM SLIGHTLY FARTHER TO THE SOUTHEAST THAN THE
GFS/GEFS, WHICH BRINGS POPS INTO THE REGION MORE QUICKLY. DID DECIDE
TO SLIGHTLY BACK OFF THE ARRIVAL OF CHANCE POPS TUESDAY NIGHT, AND
MADE MINIMAL CHANGES TO POPS ON WEDNESDAY. MODELS ARE NOW BEGINNING
TO SHOW A SPLIT IN PRECIPITATION WEDNESDAY NIGHT, WITH ONE AREA
FOCUSED ALONG THE APPALACHIAN MOUNTAINS AND A SECOND AREA FOCUSED
ALONG THE GULF STREAM, POTENTIALLY SPLITTING THE CENTRAL PART OF THE
STATE. HAVE EXPANDED LIKELY POPS TO ALL LOCATIONS, BUT RIGHT NOW
THIS LOOKS LIKE A HIGH POP/LOW QPF SCENARIO, WHERE THERE IS A GOOD
CHANCE OF RAIN WITH LOW OVERALL RAINFALL AMOUNTS. LOWS TUESDAY NIGHT
WILL RANGE FROM THE MID 40S TO THE MID 50S. WEDNESDAY WILL BE
ANOTHER WARM DAY WITH SOUTHERLY FLOW, AND HIGHS WILL RANGE FROM THE
MID 60S TO THE MID 70S. AS THE COLD FRONT MOVES THROUGH WEDNESDAY
NIGHT, LOWS WILL FALL INTO THE 40S EVERYWHERE.
LONG TERM /THURSDAY THROUGH SUNDAY/
AS OF 305 AM MONDAY...
MODELS CONTINUE TO SPEED UP THE DEPARTURE OF THE COLD FRONT, AND
HAVE REMOVED ALL POPS ON THURSDAY. LOW PRESSURE ACROSS THE NORTHERN
PLAINS ON THURSDAY WILL REACH THE OHIO RIVER VALLEY BY FRIDAY
MORNING. THE OHIO RIVER VALLEY LOW WILL WEAKEN AS IT MOVES TO THE
SOUTHEAST, BRINGING LITTLE MORE THAN SKY COVER AND NO CHANCE OF
RAIN. HIGH PRESSURE WILL THEN DOMINATE THE FORECAST OVER THE
WEEKEND, WITH THE CENTER DROPPING FROM MANITOBA ON SATURDAY INTO THE
PLAINS ON SUNDAY. AFTER NEAR NORMAL HIGHS IN THE 50S THURSDAY AND
FRIDAY, NORTHERLY FLOW WILL PLUNGE HIGHS INTO THE 40S ON SATURDAY
AND INTO THE 30S/40S ON SUNDAY. LOWS WILL BE NEAR FREEZING THURSDAY
AND FRIDAY NIGHTS, THEN DROP INTO THE UPPER TEENS AND 20S SATURDAY
NIGHT.
AVIATION /12Z MONDAY THROUGH FRIDAY/
AS OF 725 AM MONDAY...
LIFR-IFR RESTRICTIONS OVER ALL BUT SERN NC, INCLUDING AT FAY, WILL
PERSIST THROUGH MOST OF THE MORNING. ADDITIONALLY, OCCASIONAL
DRIZZLE AND LIGHT RAIN WILL ACCOMPANY THOSE FLIGHT RESTRICTIONS AT
PIEDMONT SITES AND MORE BRIEFLY AT RWI THIS MORNING. MATURE COLD AIR
DAMMING WILL MAINTAIN IFR RESTRICTIONS AT INT/GSO FOR MOST/ALL OF
THE DAY, WHILE A SOUTHEAST TO NORTHWEST IMPROVEMENT THROUGH MVFR AND
LIKELY TO VFR AT RWI AND RDU SHOULD RESULT THIS AFTERNOON.
WIDESPREAD LIFR-IFR RESTRICTIONS ARE EXPECTED AGAIN TONIGHT-TUE
MORNING. MARGINAL LOW-LEVEL WIND SHEAR WILL ALSO BE POSSIBLE OVER
THE PIEDMONT LATE TONIGHT-TUE MORNING.
OUTLOOK: FLIGHT RESTRICTIONS AT INT/GSO WILL LIKELY FLUCTUATE
BETWEEN IFR-MVFR BY DAY AND LIFR-IFR BY NIGHT THROUGH WEDNESDAY
MORNING, AS COLD AIR DAMMING HOLDS OVER THE NW NC PIEDMONT.
MEANWHILE TO THE EAST, FLIGHT RESTRICTIONS ARE LIKELY TO BE CONFINED
MAINLY TO THE LATE NIGHT-MORNING HOURS THROUGH THE SAME TIME.
RAH WATCHES/WARNINGS/ADVISORIES
NONE.
SYNOPSIS...MWS
NEAR TERM...MWS
SHORT TERM...GREEN
LONG TERM...GREEN
AVIATION...MWS
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