064
FXUS62 KRAH 190216
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
915 PM EST WED DEC 18 2024
SYNOPSIS
AN UPPER LEVEL DISTURBANCE OVER THE MISSISSIPPI VALLEY WILL SHIFT
EASTWARD OVER THE SOUTHEAST STATES AND CAROLINAS THROUGH EARLY
THURSDAY, DRAGGING A STRONG SURFACE COLD FRONT ACROSS THE AREA. A
COOLER AIR MASS WILL BUILD IN LATE THURSDAY THROUGH FRIDAY, THEN A
SECOND COLD FRONT AND UPPER LEVEL DISTURBANCE WILL MOVE THROUGH
FRIDAY NIGHT, BRINGING ARCTIC AIR INTO THE REGION FOR THE WEEKEND.
NEAR TERM /THROUGH TONIGHT/
AS OF 915 PM WEDNESDAY...
* WIDELY SCATTERED TO SCATTERED SHOWERS WILL SPREAD EAST ACROSS THE
AREA LATE THIS EVENING AND OVERNIGHT.
SURFACE COLD FRONT HAS PROGRESSED EASTWARD INTO THE NC MTNS AND
FOOTHILLS AND WILL CROSS THE AREA OVERNIGHT AND SHOULD EXIT THE SE
ZONES JUST BEFORE DAYBREAK. MEANWHILE, H5 HEIGHT FALLS ON THE
ORDER OF 50 METERS WILL CONTINUE TO OVERSPREAD THE AREA AS THE
TRAILING PARENT MID/UPPER LEVEL MOVES OVER THE AREA THURSDAY
MORNING.
THE PRE-FRONTAL SHOWERS AND THUNDERSTORMS TRAINING OVER THE SOUTHERN
COASTAL PLAIN AND EASTERN SANDHILLS HAS BEEN MORE ACTIVE THAN HI-RES
MODEL GUIDANCE ADVERTISED. HOWEVER, GIVEN THAT THE 500-1000 J/KG
FROM EARLIER IN THE DAY IS STARTING TO WEAKEN AND COLLAPSE
SOUTHWARD, SHOULD START THIS AREA OF CONVECTION BECOME A LITTLE LESS
ORGANIZED. OTHERWISE, SCATTERED SHOWERS AND STORMS WILL CONTINUE TO
FORM AND MOVE EAST AHEAD OF THE COLD FRONT AND APPROACHING TROUGH,
AND SHOULD LARGELY END/EXIT THE AREA TOWARD 08-10Z.
PATCHY FOG WILL ALSO BE APT TO FORM WITHIN THE WARM SECTOR AHEAD OF
THE FRONT, MAINLY ACROSS THE SOUTHERN COASTAL PLAIN AND SANDHILLS.
IT WILL TAKE AWHILE BUT COOLER AND DRIER AIR WILL SPILL INTO THE
REGION BEHIND THE FRONT LATE TONIGHT AND IN MOST CASES AFTER
DAYBREAK. LOWS IN THE MID 40S NEAR THE VA BORDER AND LOWER 50S
ACROSS THE SOUTH.
SHORT TERM /THURSDAY THROUGH SATURDAY NIGHT/
AS OF 240 PM WEDNESDAY...
THE MAIN STORIES FOR THIS PERIOD WILL BE THE POTENT UPPER PV MAX
THAT CROSSES THE CAROLINAS FRI AFTN/NIGHT, FOLLOWED BY THE ARRIVAL
OF ARCTIC AIR.
THU/THU NIGHT: THE SURFACE COLD FRONT IS EXPECTED TO BE SE OF THE
FORECAST AREA BY DAYBREAK THU, HOWEVER THE NORTHERN PORTIONS OF THE
SOUTHERN STREAM SHORTWAVE TROUGH WILL BE OVERHEAD, SHIFTING
EASTWARD, AND THERE MAY BE SUFFICIENT LOW LEVEL (ESP 925-850 MB)
MOISTURE DESPITE THE INCREASING LOW LEVEL STABILITY TO SQUEEZE OUT
ISOLATED PATCHES OF VERY LIGHT RAIN OR DRIZZLE IN THE E EARLY THU
MORNING. ANY BRIEF FAIR SKIES ARE LIKELY TO FILL IN WITH STRATOCU IN
THE AFTN AS MOIST UPGLIDE AT 285-290K RAMPS UP OVER ALL BUT OUR
EXTREME W AND BECOMES TRAPPED WITHIN THE LOWER REACHES OF THE STABLE
LAYER EVIDENT FROM 925-800 MB. WITH DECENT MIXING IN THE LOWEST 50
MB, HOWEVER, WE SHOULD SEE A FEW GUSTS IN THE MORNING THROUGH EARLY
AFTN, UNTIL THE LOW LEVEL PRESSURE GRADIENT RELAXES. EXPECT HIGHS IN
THE 50S, NEAR TO A DEGREE OR SO ABOVE NORMAL, AS THE INCOMING AIR
MASS WILL BE RELATIVELY MILD WITH ABOVE-CLIMO LOW LEVEL THICKNESSES.
WITH NOCTURNAL STABILIZATION AT THE SURFACE THU NIGHT RESULTING IN A
DEEP STABLE LAYER WITH WEAK WINDS INHIBITING ANY MIXING AND
DISPERSION OF THIS MOISTURE JUST ALOFT, SKIES ARE LIKELY TO REMAIN
MOSTLY CLOUDY TO CLOUDY THROUGH THE NIGHT, AS SURFACE HIGH PRESSURE
RIDGING EXTENDS WEAKLY ACROSS THE AREA FROM THE NE. THESE CLOUDS
WILL HELP KEEP LOWS AT OR ABOVE NORMAL, IN THE 30S.
FRI-FRI NIGHT: A STRONG SHORTWAVE TROUGH NOW OVER THE PACNW WILL
TRACK SE THROUGH THE MIDWEST THROUGH THU AND, WITH THE ADDED PUNCH
OF A SERIES OF SHEARED VORTICITY STREAKS SWINGING THROUGH ITS BASE,
WILL MOVE THROUGH NC FRI AFTN/EVENING, ACCOMPANIED BY AN ARCTIC
SURFACE COLD FRONT. INCREASING LOW LEVEL WSW AND W FLOW FRI MORNING
SHOULD HELP SCOUR OUT THE STRATOCU OVER THE AREA FROM SW TO NE,
RESULTING IN A PERIOD OF FAIR SKIES, ALTHOUGH THIS WILL QUICKLY GIVE
WAY TO INCREASING CLOUDS ONCE AGAIN. WITH A TROP FOLD LIKELY AND THE
TROPOPAUSE DIPPING TO BELOW 500 MB, A STEEPENING OF LAPSE RATES
BELOW 600 MB IS EXPECTED, ALONG WITH A MOISTENING OF THE LOW LEVEL
COLUMN. A CHANCE OF SHOWERS IS STILL EXPECTED LATE FRI INTO FRI
NIGHT. WHILE THE PROJECTED ELEVATED/SHALLOW CAPE IS QUITE SMALL,
GIVEN THE STRONG PV MAX AND THE ANTICIPATED MOISTENING UP INTO THE
MIXED PHASE REGION ALOFT, A FEW LIGHTNING STRIKES ARE POSSIBLE. THE
ARCTIC FRONT WILL PUSH ESE AND OFFSHORE FRI NIGHT, RESULTING IN
CLEARING W TO E OVERNIGHT, AND A PERIOD OF GUSTY WINDS IS POSSIBLE.
HIGHS IN THE UPPER 40S TO MID 50S, FOLLOWED BY LOWS FROM THE UPPER
20S TO MID 30S.
SAT/SAT NIGHT: THE POTENT SHORTWAVE TROUGH WILL HAVE PUSHED WELL
OFFSHORE, INDUCING MID LEVEL SUBSIDENCE, BUT WE'LL REMAIN WITHIN A
LONGWAVE MID LEVEL TROUGH EXTENDING DOWN THROUGH E NOAM SAT/SAT
NIGHT. MINOR PERTURBATIONS (WITH LOW INDIVIDUAL PREDICTABILITY) ARE
LIKELY TO SWING THROUGH THE REGION WITHIN BROADLY CYCLONIC WNW FLOW,
BUT WITH DEEP MOISTURE LACKING, WE SHOULD SEE LITTLE MORE THAN SOME
HIGH CLOUDINESS (PERHAPS OROGRAPHICALLY ENHANCED ACROSS OUR N AND
INTO VA) TOPPING SOME HIGH-BASED FLAT AFTN CU THAT WILL FORM WITH
MIXING. THE TIGHT POST-FRONT MSLP GRADIENT SAT MORNING WILL
RESULTING IN A CHILLY NW BREEZE EARLY IN THE DAY, WITH WINDS
LIGHTENING LATE AS THAT GRADIENT RELAXES. EXPECT HIGHS IN THE 40S,
AND LOWS IN THE UPPER TEENS TO MID 20S. -GIH
LONG TERM /SUNDAY THROUGH WEDNESDAY/
AS OF 330 PM WEDNESDAY...
AS STRONG HIGH PRESSURE OF 1040 MB BUILDS TO THE NORTH AND THE
MID/UPPER LEVEL TROUGH MOVES OFFSHORE, SUNDAY WILL BE THE COLDEST
DAY OF THE PERIOD. HIGH TEMPERATURES SUNDAY SHOULD BE IN THE UPPER
30S TO LOW 40S, WHILE LOWS SUNDAY NIGHT WILL DIP INTO THE UPPER
TEENS AND LOW 20S.
TEMPERATURES WILL SLOWLY MODERATE THROUGH THE BEGINNING OF NEXT WEEK
AS THE SURFACE HIGH STARTS TO WEAKEN AND MOVE OFFSHORE AND MID/UPPER
LEVEL FLOW TURNS TO QUASI-ZONAL. THUS, MONDAY WILL HAVE HIGH
TEMPERATURES IN THE LOW TO MID 40S, WITH LOWS IN THE LOW TO MID 20S.
HIGH TEMPERATURES ON TUESDAY WILL BE IN THE MID 40S TO MID 50S, WITH
LOWS IN THE 30S TUESDAY NIGHT.
UNSETTLED WEATHER MAY RETURN ON CHRISTMAS AS A TROUGH AND ASSOCIATED
COLD FRONT APPROACHES THE REGION. MODELS DIFFER IN THE STRENGTH OF
THE TROUGH AND HOW MUCH PRECIPITATION THEY PUT OVER CENTRAL NORTH
CAROLINA. THE GFS SHOWS A DEEPER TROUGH AND INCREASED PRECIPITATION
AND THE ECMWF SHOWS A MUCH WEAKER AND SLOWED TROUGH WITH MUCH LESS
PRECIPITATION. PRECIPITATION SHOULD ARRIVE AFTER DAYBREAK.
TEMPERATURES SHOULD BE ABOVE FREEZING, SO ANY PRECIPITATION THAT
DOES FALL SHOULD BE RAIN.
AVIATION /00Z THURSDAY THROUGH MONDAY/
AS OF 740 PM WEDNESDAY...
24 HOUR TAF PERIOD: A COLD FRONT AND ASSOCIATED LINE OF SHOWERS ARE
BEGINNING TO MOVE ACROSS THE NW PIEDMONT. WHILE THE LINE IS
WEAKENING AND NO MORE THUNDER IS CURRENTLY OBSERVED WITH IT, IT IS
STILL RESULTING IN A PERIOD OF MVFR CEILINGS AT INT AND GSO. BEHIND
THE FRONT, DRY WEATHER AND VFR CONDITIONS ARE EXPECTED ACROSS THE NW
(INCLUDING INT/GSO) THROUGH THE REST OF THE TAF PERIOD. FARTHER
EAST, HOWEVER, ISOLATED SHOWERS AND STORMS WILL BE POSSIBLE THROUGH
LATE THIS EVENING AS THE LINE POTENTIALLY REDEVELOPS AND FROM A FEW
DISCRETE CELLS OUT AHEAD OF IT, PARTICULARLY AT FAY AND RWI. MVFR
CEILINGS AND VISIBILITIES WILL BE POSSIBLE. ANY RAIN SHOULD PUSH
EAST OF CENTRAL NC AFTER 06Z. A BRIEF WINDOW OF IFR CEILINGS AND
VISIBILITIES IS POSSIBLE AFTER THIS TIME BEFORE THE FRONT MOVES
THROUGH, BUT THE LATEST HIGH-RES GUIDANCE LARGELY KEEPS IT EAST OF
THE TAF TERMINALS. MVFR CEILINGS ARE EXPECTED TO LINGER AT FAY
THROUGH TOMORROW AFTERNOON, AND WHILE THERE IS SOME UNCERTAINTY HOW
LONG THEY WILL LAST AT RDU AND RWI, THE POTENTIAL WILL AT LEAST BE
THERE THROUGH THE MORNING HOURS. SW WINDS AROUND 5-10 KTS WILL
QUICKLY SHIFT TO NW THEN N TONIGHT BEHIND THE COLD FRONTAL PASSAGE.
SOME POST-FRONTAL GUSTINESS WILL ALSO BE POSSIBLE. NE WINDS AROUND 8-
12 KTS WITH GUSTS OF 15-20 KTS ARE EXPECTED DURING THE DAY TOMORROW,
GRADUALLY DIMINISHING IN THE AFTERNOON.
OUTLOOK: ANOTHER WEATHER SYSTEM WILL BRINGING A CHANCE OF SHOWERS
AND A THREAT OF SOME MVFR RESTRICTIONS ON FRIDAY. BEHIND THIS
SYSTEM, COLD ARCTIC AIR WILL SPREAD INTO THE REGION ACCOMPANIED BY
GUSTY NORTHWEST WINDS FRIDAY NIGHT AND SATURDAY. FAIR WEATHER IS
EXPECTED FOR SUNDAY AND MONDAY. -BLAES
RAH WATCHES/WARNINGS/ADVISORIES
NONE.
SYNOPSIS...HARTFIELD
NEAR TERM...CBL
SHORT TERM...HARTFIELD
LONG TERM...HELOCK
AVIATION...DANCO/BLAES
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