899
FXUS62 KRAH 190707
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
205 AM EST THU DEC 19 2024
SYNOPSIS
AN UPPER LEVEL DISTURBANCE WILL SHIFT EASTWARD OVER THE SOUTHEAST
STATES AND CAROLINAS EARLY 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 /TODAY THROUGH TONIGHT/
AS OF 150 AM THURSDAY...
WITH BRIEF EXCEPTIONS, OUR SKIES ARE EXPECTED TO BE MOSTLY CLOUDY TO
OVERCAST TODAY. THE COLD FRONT IS ANALYZED FROM THE DELMARVA ACROSS
E AND S VA AND THROUGH W NC, JUST SE OF THE MID LEVEL SHORTWAVE
TROUGH THAT IS NOTED ON WV IMAGERY NOW PUSHING INTO W NC. THE
PREFRONTAL BAND OF LIGHT SHOWERS NOW MOVING THROUGH THE PIEDMONT
(AND ALIGNED WITH THE WESTERN EDGE OF THE 1" PW AREA) WILL PROGRESS
E THROUGH THE CWA, ALTHOUGH SHOWERS WILL REMAIN SPOTTY AND SPARSE.
AS THE MID LEVEL TROUGH PLOWS E, THE COLD FRONT IS EXPECTED TO PUSH
SE OF THE FORECAST AREA BY DAYBREAK, WITH THE COOLER AIR FILTERING
IN FROM THE N AND W. ANY BRIEFLY FAIR SKIES BEHIND THE FRONT (MOST
LIKELY ACROSS THE FAR N) WILL FILL IN QUICKLY WITH BKN-OVC STRATOCU
AS MOIST UPGLIDE AT 285-290K RAMPS UP OVER MUCH OF THE AREA, WHILE
THE VERTICAL SHEAR (WSW WINDS ABOVE 850 MB AND NE WINDS BELOW) AND
DEEP STABLE LAYER FROM 950 TO 800 MB WILL KEEP THE MOISTURE TRAPPED
AND RESISTANT TO MIXING AND DISPERSION. SHALLOW POST-FRONTAL MIXING
IN THE LOWEST 50 MB, HOWEVER, WILL PROMPT SOME GUSTINESS THIS
MORNING THROUGH MID AFTN, UNTIL THE LOW LEVEL PRESSURE GRADIENT
RELAXES. DESPITE THE VERY LIMITED INSOLATION, ABOVE NORMAL
THICKNESSES FAVOR HIGHS FROM AROUND 50 N TO THE MID 50S S, WITHIN A
DEGREE OR SO OF NORMAL, AS THE INCOMING AIR MASS WILL BE RELATIVELY
MILD (ALBEIT COOLER THAN WE HAVE BEEN). NOCTURNAL STABILIZATION AT
THE SURFACE TONIGHT WILL RESULT IN A DEEP STABLE LAYER WITH
WEAKENING WINDS STILL INHIBITING MIXING AND DISPERSION OF THE
MOISTURE JUST ALOFT, AND SEVERAL HIGH RES MODELS SUGGEST THAT PATCHY
PREDAWN VERY LIGHT RAIN OR DRIZZLE IS POSSIBLE LATE TONIGHT, MAINLY
ACROSS THE N AND E, AND WILL ADD IN A SLIGHT CHANCE POP IN THESE
AREAS LATE TONIGHT. 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 MID 30S TO AROUND 40. -GIH
SHORT TERM /FRIDAY 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.
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 /SATURDAY THROUGH WEDNESDAY/
AS OF 205 AM THURSDAY...
WELL BELOW NORMAL TEMPERATURES ARE EXPECTED INTO EARLY NEXT WEEK.
THEREAFTER, A MODERATING TREND IS EXPECTED WITH A SLIGHT UPTICK IN
RAIN CHANCES BY MIDWEEK.
NORTHWEST FLOW ALOFT WILL BE IN PLACE SAT AND SUN. AT THE SURFACE,
AN ANOMALOUSLY STRONG 1040 MB ARCTIC HIGH OVER THE UPPER MS VALLEY
AND GREAT LAKES REGION SAT INTO SUN WILL GRADUALLY SETTLE INTO THE
MID-ATLANTIC REGION BY MON. WHILE CHILLIER AIR WILL ARRIVE SAT
BEHIND THE DEPARTING SYSTEM FRI NIGHT, ARCTIC AIR WILL NOT FILTER IN
UNTIL SAT NIGHT AND SUN MORNING, WHEN THE HIGH BUILDS INTO THE LOWER
GREAT LAKES. AS A RESULT, WE ARE BELOW AVERAGE BY ABOUT 5-8 DEGREES
IN THE MID 40S TO NEAR 50. AS THE ARCTIC AIR BUILDS INTO THE REGION
SAT NIGHT, WE SHOULD SEE LOW DIP SOME 9-12 DEGREES BELOW AVERAGE IN
THE UPPER TEENS TO LOW 20S. A FAST-MOVING SHORTWAVE WILL AGAIN MOVE
OVERHEAD SAT NIGHT AND COULD PRODUCE SOME OROGRAPHIC CIRRUS. THE GFS
ACTUALLY SHOWS SOME DECENT HIGH-LEVEL MOISTURE VIA FORECAST
SOUNDINGS, WHICH COULD LIMIT RADIATIONAL COOLING SOMEWHAT.
THE ARCTIC AIR WILL BE WELL ENTRENCHED SUN AND MON, WITH HIGHS SOME
12-18 DEGREES BELOW IN THE UPPER 30S TO LOW 40S, COLDEST ON SUN.
EXCELLENT RADIATIONAL COOLING SUN NIGHT WITH THE SURFACE HIGH TO OUR
NORTH WILL MAKE FOR OUR COLDEST NIGHT IN THE MID TEENS TO LOW 20S.
AS WE HEAD INTO THE EARLY TO MIDDLE OF NEXT WEEK, RIDGING WILL BUILD
ALOFT MON AND TRANSITION TO QUASI-ZONAL FLOW COME TUE. IT LOOKS LIKE
WE WILL BE IN A SPLIT FLOW, WITH THE NORTHERN JET STREAM OVER THE
GREAT LAKES AND THE SUBTROPICAL JET OVER THE GULF. A SYSTEM WILL
SKIRT TO OUR NORTH MON AND TUE. ENSEMBLES THEN SHOW A POTENTIAL
SHORTWAVE IN THE PERTURBED FLOW PERHAPS REACHING OUR AREA COME
CHRISTMAS DAY. ALTHOUGH PW'S INCREASE TO THE 75TH PERCENTILE FOR
LATE DECEMBER, SOLUTIONS VARY ON THE HOW THE SYSTEM EVOLVES AS IT
TRACKS EASTWARD, AS WELL AS THE DEGREE OF RIDGING OFF THE SE COAST.
AS A RESULT, CONFIDENCE IS LOW ON SPECIFICS SO KEPT RAIN CHANCES IN
THE 20-30 PERCENT RANGE. EITHER WAY, THE AIRMASS IS WELL ABOVE
FREEZING SO ANY PRECIPITATION THAT DOES FALL WOULD BE ALL LIQUID.
HIGHS MON-WED SHOULD SEE A WARMING TREND FROM THE UPPER 40S TO LOW
50S TUE TO THE LOW TO UPPER 50S ON CHRISTMAS.
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...HARTFIELD
SHORT TERM...HARTFIELD
LONG TERM...KREN
AVIATION...HARTFIELD
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