423
FXUS62 KRAH 191127
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
625 AM EST THU DEC 19 2024
SYNOPSIS
A COLD FRONT WILL SETTLE TO OUR SOUTHEAST TODAY, AS WEAK HIGH
PRESSURE PUSHES IN FROM THE NORTH. AN ARCTIC COLD FRONT AND STRONG
UPPER LEVEL DISTURBANCE WILL APPROACH FROM THE WEST LATE TONIGHT AND
CROSS THE AREA FRIDAY THROUGH EARLY FRIDAY NIGHT. THIS WILL BRING
MUCH COLDER AIR INTO THE REGION FOR THE WEEKEND.
NEAR TERM /TODAY THROUGH TONIGHT/
AS OF 150 AM THURSDAY...
WITH BRIEF EXCEPTIONS, PARTICULARLY THIS MORNING, OUR SKIES ARE
EXPECTED TO BE MOSTLY CLOUDY 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 AND FRIDAY NIGHT/
AS OF 245 AM THURSDAY...
PASSAGE OF A POTENT UPPER PV MAX AND ARCTIC SURFACE FRONT FRI WILL
BRING A CHANCE OF SHOWERS FRI AND DRAW MARKEDLY COLDER AIR INTO THE
REGION STARTING FRI NIGHT.
A STRONG SHORTWAVE TROUGH NOW DIVING THROUGH THE DAKOTAS WILL TRACK
SE THROUGH THE MIDWEST TODAY AND, AS A SERIES OF SHEARED VORTICITY
LOBES STREAK THROUGH ITS BASE, WILL MOVE THROUGH NC FRI AFTN AND
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.
MODELS CONTINUE TO INDICATE A PRONOUNCED TROPOPAUSE FOLD WITH THE 2
PVU SURFACE EXTENDING BELOW 600 MB, RESULTING IN A STEEPENING OF
LAPSE RATES AND MOISTENING OF THE COLUMN THROUGH THE LOWEST 10K-
12KFT. AS SUCH, SCATTERED SHOWERS ARE STILL EXPECTED FRI INTO EARLY
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 BRIEF PERIOD OF GUSTY WINDS IS
POSSIBLE. EXPECT HIGHS IN THE UPPER 40S TO MID 50S, FOLLOWED BY LOWS
FROM THE UPPER 20S TO MID 30S. -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 /12Z THURSDAY THROUGH MONDAY/
AS OF 625 AM THURSDAY...
WE WILL GENERALLY SEE VFR CONDITIONS PREVAILING ACROSS THE N AND W
DURING THE DAYTIME TODAY WITH MVFR CONDITIONS IN THE SE, HOWEVER
THESE LOWER CLOUDS ARE MORE SCATTERED THIS MORNING THAN EARLIER
THOUGHT, AND THIS HIGH TEMPORAL VARIATION IN AVIATION CONDITIONS HAS
REDUCED FORECAST CONFIDENCE. THE COLD FRONT THAT DROPPED SOUTHEAST
THROUGH THE AREA EARLIER THIS MORNING IS SETTLING TO OUR SE, AND THE
CLOUDS HAVE TEMPORARILY BROKEN UP AND GONE SCATTERED ESPECIALLY AT
INT/GSO. AFTER A PERIOD OF FAIR SKIES ESPECIALLY ACROSS THE NW
TERMINALS, CLOUDS SHOULD REDEVELOP AREAWIDE THIS AFTERNOON, WITH
MAINLY VFR CIGS PERIODICALLY BECOMING MVFR AT INT/GSO/RDU/RWI WHILE
FAY REMAINS MOSTLY UNDER MVFR CIGS THROUGH THE DAY. CIGS ARE
EXPECTED TO LOWER AREAWIDE AFTER NIGHTFALL TO MVFR, WHICH SHOULD
PERSIST THROUGH THE END OF THE TAF VALID PERIOD. ISOLATED PATCHY
DRIZZLE OR LIGHT RAIN IS POSSIBLE VERY LATE TONIGHT, AFTER 09Z,
MAINLY IN THE E. SURFACE WINDS WILL BE FROM THE NE AND ENE TODAY, 10-
15 KTS WITH A FEW GUSTS TO 15-20 KTS THROUGH EARLY AFTERNOON,
FOLLOWED BY DECREASING WINDS TO UNDER 10 KTS.
LOOKING BEYOND 12Z FRI, AN APPROACHING ARCTIC COLD FRONT WILL BRING
A FEW SHOWERS WITH POSSIBLE SUB-VFR CONDITIONS FRI. A PERIOD OF
GUSTY WINDS IS POSSIBLE FRI INTO SAT. VFR CONDITIONS ARE EXPECTED
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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