026
FXUS62 KRAH 182002
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
300 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 300 PM WEDNESDAY...
* A WARM AND MOIST AIRMASS IS WELL ESTABLISHED ACROSS CENTRAL NC
WITH TEMPERATURES IN THE UPPER 60S TO LOWER 70S WHICH IS ABOUT 15
TO 20 DEGREES ABOVE AVERAGE.
* WIDELY SCATTERED TO SCATTERED SHOWERS WILL SPREAD ACROSS THE AREA
LATE THIS AFTERNOON AND OVERNIGHT. RAIN CHANCES AND COVERAGE
CONTINUE TO TREND DOWN WITH THIS EVENT.
THE LATEST SURFACE ANALYSIS SHOWS A WEAK SURFACE FRONT EXTENDING
WEST TO EAST NEAR THE VA BORDER WITH A WARM AND MOIST AIRMASS ACROSS
NC. TEMPERATURES ACROSS CENTRAL NC RANGE IN THE UPPER 60S TO LOWER
70S ( ~15 TO 20 DEGREES ABOVE AVERAGE) WITH DEW POINTS IN THE UPPER
50S TO LOWER 60S. THE LATEST SURFACE ANALYSIS EVEN SHOWS ~500 J/KG
OF MLCAPE ACROSS THE SOUTHERN TIER. VISIBLE SATELLITE IMAGERY SHOWS
A GOOD DEAL OF STRATOCUMULUS ACROSS THE AREA BUT NO PRECIPITATION IN
OR NEAR CENTRAL NC.
A STRONGER COLD FRONT CURRENTLY EXTENDS FROM EASTERN KY SOUTHWEST
INTO TN AND AL. AHEAD OF THIS FRONT AND A PARENT MID/UPPER LEVEL
TROUGH EXTENDS A BAND OF SHOWERS AND A FEW THUNDERSTORMS FROM
SOUTHERN WV ACROSS FAR EASTERN TN AND INTO NORTHERN GA. THIS BAND OF
MODEST CONVECTION WILL SHIFT EAST LATE THIS AFTERNOON AND SLOWLY
WEAKEN AS IT MOVES INTO THE WESTERN PIEDMONT THIS EVENING AS THE
UPPER LEVEL FORCING WEAKENS A BIT. IN ADDITION, SCATTERED SHOWERS
ACROSS CENTRAL AND EASTERN SC WILL SPREAD NORTHEAST INTO THE
SANDHILLS AND SOUTHERN COASTAL PLAIN THIS EVENING. AS THE CONVECTION
MOVING ACROSS THE WESTERN PIEDMONT FADES, CONVECTION IN THE SOUTH
AND EAST WILL MODESTLY INCREASE IN COVERAGE AND INTENSITY DURING THE
EVENING AND OVERNIGHT AS IT MOVES ACROSS THE EASTERN PIEDMONT,
SANDHILLS AND COASTAL PLAIN. THE PRECIPITATION WILL SHIFT EAST
OVERNIGHT AND LARGELY END/EXIT THE AREA TOWARD 08 OR 10Z. CAN'T RULE
OUT A NARROW BAND OF ISOLATED SHOWERS ASSOCIATED WITH THE FRONT AS
IT DROPS SOUTHEAST LATE TONIGHT. WITH A WEAKLY UNSTABLE AIRMASS A
FEW THUNDERSTORMS ARE POSSIBLE, PRIMARILY IN THE SOUTH AND
SOUTHEAST. IT WILL TAKE AWHILE BUT COOLER AND DRIER AIR WILL SPILL
INTO THE REGION BEHIND THE FRONT LATE TONIGHT WITH LOWS IN THE MID
40S NEAR THE VA BORDER AND LOWER 50S ACROSS THE SOUTH. -BLAES
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 /FRIDAY THROUGH TUESDAY/
AS OF 230 AM WEDNESDAY...
THE STRONG TROUGH FROM THU NIGHT IS FORECAST TO STRENGTHEN AS IT
MOVES ACROSS OUR REGION FRI AFTERNOON AND EVENING. MUCH OF THE 00Z
SUITE OF THE GFS/CMC/ECMWF ARE IN VERY GOOD AGREEMENT WITH THE TRACK
AND TIMING OF THE VORT MAX MOVING SOUTHEAST. THE VORT MAX IS LARGELY
FORECAST TO MOVE DIRECTLY OVERHEAD CENTRAL NC CENTERED AROUND EARLY
EVENING, WITH IMPRESSIVE 180+ M HEIGHT FALLS. THERE IS A CHANCE OF
SOME LIGHT RAIN OR DRIZZLE EAST OF US-1 FRI MORNING TO EARLY
AFTERNOON ASSOCIATED WITH LOW-LEVEL ISENTROPIC ASCENT ATOP THE
SURFACE WEDGE. HOWEVER, FEEL THE BETTER CHANCE OF LIGHT RAIN WILL BE
LATE FRI AFTN AND EVENING WITH THE VORT MAX. MODELS ALSO SHOW A
SURFACE TROUGH AXIS AND PERHAPS A WEAK SURFACE LOW ALONG SC,
TRACKING SE WITH THE MID-LEVEL VORT MAXIMA. ENSEMBLE GUIDANCE WAS
ALSO TRENDING WITH HIGHER POP CHANCES. WE RAISED POPS ACCORDINGLY
(30-PERCENT) IN THE LATE AFTN/EVE AREA-WIDE EXCEPT THE FAR SOUTHERN
PIEDMONT. HIGHS FRI IN THE LOW/MID 50S. IT LOOKS LIKE THE VORT MAX
MOVES EAST BEFORE THE MUCH COLDER AIR MOVES IN. MODEL SOUNDINGS AND
PTYPE NOMOGRAMS ALSO SHOW THIS, SUCH THAT ANY PTYPE CONCERNS ARE NOT
ANTICIPATED THUS FAR.
IT IS ALL ABOUT MUCH COLDER AIR SAT TO EARLY NEXT WEEK AS COLD HIGH
PRESSURE OVER THE UPPER MS VALLEY SAT EVENTUALLY SETTLES INTO THE
MID-ATLANTIC COME MONDAY. AN ARCTIC FRONT WILL MOVE THROUGH SAT
NIGHT. LOW-LEVEL THICKNESSES BECOMING LOWEST SUN INTO MON AROUND
1265-1270 M, SOME 40-45 M BELOW AVERAGE. ANOTHER VORT MAX IS
FORECAST IN THE GUIDANCE/ENSEMBLES TO MOVE THROUGH LATE SAT INTO SUN
WITH THE NW FLOW ALOFT, BUT CURRENT INDICATIONS POINT TO A FURTHER
SOUTH AND WEST TRACK SUCH THAT WE KEPT THE FORECAST DRY FOR NOW.
HIGHS SAT WILL FALL FURTHER INTO THE LOW TO MID/UPPER 40S. HIGHS
SUN/MON WILL BE SOME 12-16 DEGREES BELOW AVERAGE IN THE UPPER 30S TO
LOW 40S AND LOWS IN THE MID TEENS TO LOW 20S, COLDEST MON MORNING
UNDER THE ANOMALOUSLY STRONG 1040 MB SURFACE HIGH.
ENSEMBLE DATA SHOWS THAT RIDGING TO QUASI-ZONAL FLOW IS FORECAST TO
BUILD IN MON AND TUE AT MID-LEVELS, WHILE THE COLD SURFACE HIGH
SLOWLY RETREATS NORTHWARD. THIS SHOULD FAVOR WARMER HIGHS BY TUE IN
THE MID 40S TO LOW 50S.
AVIATION /18Z WEDNESDAY THROUGH MONDAY/
AS OF 225 PM WEDNESDAY...
24 HOUR TAF PERIOD: WIDESPREAD IFR AND LIFR FOG AND STRATUS ACROSS
CENTRAL NC EARLY THIS MORNING HAS ERODED AND LIFTED WITH AREAS OF
MAINLY MVFR AND ISOLATED IFR STRATUS ACROSS THE AREA, ESPECIALLY
FROM RALEIGH SOUTH AND EAST. ADDITIONAL IMPROVEMENT IN SKY
CONDITIONS IS LIKELY TO CONTINUE INTO THE AFTERNOON WITH VFR TO MVFR
CONDITIONS EXPECTED WITH AREAS OF STRATOCUMULUS WITH BASES OF 2.5 TO
4 KFT.
A COLD FRONT AND MID/UPPER LEVEL TROUGH WILL APPROACH FROM THE WEST
AND MOVE ACROSS THE AREA TONIGHT AND EARLY THURSDAY PRODUCING WIDELY
SCATTERED SHOWERS THAT WILL SHIFT EAST THIS EVENING INTO THE
OVERNIGHT. THE GREATEST CHANCE OF SHOWERS WILL BE BETWEEN 00Z AND
06Z WITH THE GREATEST THREAT ALONG WITH A SMALL CHANCE OF A
THUNDERSTORM ACROSS EASTERN LOCATIONS INCLUDING THE COASTAL PLAIN
AND SANDHILLS INCLUDING THE KFAY AND KRWI TERMINALS. GIVEN LIMITED
COVERAGE AND CONFIDENCE WILL OMIT A MENTION OF THUNDER IN THE TAFS.
SHOWERS WILL PRODUCE LOCAL CIG AND POSSIBLY VSBY RESTRICTIONS.
SOUTHWEST WINDS AT 6 TO 12 KTS WILL GUST TO AROUND 20KTS THIS
AFTERNOON. THE FRONT WILL MOVE THROUGH THE AREA FROM WEST TO EAST
BETWEEN 05 AND 10Z AND WILL BE ACCOMPANIED BY A WIND SHIFT TO THE
NORTHWEST WITH AN AREA OF LOW STRATUS DEVELOPING LATE TONIGHT ACROSS
THE COASTAL PLAIN AND SANDHILLS INCLUDING THE KFAY AND KRWI
TERMINALS. CONSIDERABLE CLOUDINESS IS EXPECTED ON THURSDAY WITH CIGS
OF 2-4KFT RESULTING IN SOME MVFR RESTRICTIONS DURING THE DAY,
ESPECIALLY SOUTH AND EAST OF RALEIGH. NORTHWEST WINDS WILL BECOME
NORTHEASTERLY AT AROUND 10KTS WITH SOME GUSTS TO AROUND 15KTS.
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...BLAES
SHORT TERM...HARTFIELD
LONG TERM...KREN
AVIATION...BLAES
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