492
FXUS62 KRAH 190600
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
100 AM EST WED DEC 18 2024
SYNOPSIS
AN UPPER LEVEL DISTURBANCE WILL SHIFT EASTWARD OVER THE SOUTHEAST
STATES AND CAROLINAS THROUGH THIS MORNING, DRAGGING A STRONG SURFACE
COLD FRONT ACROSS THE AREA. A COOLER AIR MASS WILL BUILD IN TODAY
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 /06Z THURSDAY THROUGH MONDAY/
AS OF 100 AM THURSDAY...
PERIODS OF ADVERSE AVIATION CONDITIONS REMAIN POSSIBLE ACROSS
CENTRAL NC THROUGH TONIGHT, PARTICULARLY IN THE E, AS A COLD FRONT
AND UPPER LEVEL DISTURBANCE MOVE SE THROUGH THE AREA. THE EARLIER
SOLID BAND OF SHOWERS AND ISOLATED STORMS HAS SHIFTED EAST OF THE
CENTRAL NC TERMINALS, ALTHOUGH A SECOND BAND OF MUCH LIGHTER AND
MORE PATCHY SHOWERS WILL CROSS THE AREA WITH LITTLE FANFARE THROUGH
12Z. WHILE THE SURFACE COLD FRONT WILL REMAIN TO OUR SE FROM THIS
MORNING ON, QUICKLY RETURNING MOISTURE ATOP THE INCOMING COOLER AIR
WILL RESULT IN CONSIDERABLY CLOUD COVER THROUGH TONIGHT. AT INT/GSO,
VFR CONDITIONS WILL DOMINATE FOR THE NEXT 24 HOURS, BUT WITH A CIG
MUCH OF THE TIME, AND A BRIEF PERIOD OF MVFR CIGS IS EXPECTED
BETWEEN 15Z AND 20Z. FURTHER E, AT RDU/RWI/FAY, SHALLOW FOG BANKS
WILL REDUCE VSBYS SPORADICALLY TO IFR/LIFR THROUGH 09Z WITH MOMENTS
OF IFR/LIFR CIGS. THEN, WHILE CIGS WILL BE VFR THE MAJORITY OF THE
TIME, A WINDOW OF MVFR CIGS IS EXPECTED BETWEEN 10Z AND 16Z,
ALTHOUGH FAY IS LIKELY TO SEE MVFR CIGS LAST UNTIL CLOSER TO 20Z.
SURFACE WINDS LIGHT AND VARIABLE OR LIGHT FROM THE NW WILL INCREASE
TO 10-15 KTS GUSTING TO 15-20 KTS AS THE FRONT PASSES THROUGH NW TO
SE. WINDS WILL BE FROM THE NNW THEN NE, FINALLY BECOMING ENE LATER
TODAY INTO TONIGHT.
LOOKING BEYOND 06Z FRI, SKIES WILL REMAIN MOSTLY CLOUDY INTO FRI.
ANOTHER STRONG UPPER LEVEL DISTURBANCE AND ARCTIC COLD FRONT WILL
BRING GUSTY WINDS AND A FEW SHOWERS WITH POSSIBLE SUB-VFR CONDITIONS
FRI. GUSTY WINDS MAY EXTEND INTO SAT. VFR CONDITIONS ARE EXPECTED TO
DOMINATE FROM FRI NIGHT THROUGH MON AS A COLD AIR MASS ARRIVES. -GIH
RAH WATCHES/WARNINGS/ADVISORIES
NONE.
SYNOPSIS...HARTFIELD
NEAR TERM...CBL
SHORT TERM...HARTFIELD
LONG TERM...HELOCK
AVIATION...HARTFIELD
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