271
FXUS62 KRAH 201721
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
1220 PM EST FRI DEC 20 2024
SYNOPSIS
AN ARCTIC COLD FRONT AND STRONG UPPER LEVEL DISTURBANCE WILL
APPROACH FROM THE WEST THIS MORNING AND CROSS THE AREA TODAY THROUGH
TONIGHT. THIS WILL BRING MUCH COLDER AIR INTO THE REGION FOR THE
WEEKEND.
NEAR TERM /TODAY AND TONIGHT/
AS OF 1053 AM FRIDAY...
LOW-LEVEL OVERCAST CONTINUES THIS MORNING AHEAD OF A STRONG COLD
FRONT THAT'S JUST ENTERING CENTRAL TN/KY. ALOFT, A STRONG VORTMAX
WAS EVIDENT ON SATELLITE SPIRALING SOUTHEASTWARD OVER THE IN/OH/KY
VICINITY. LATEST GUIDANCE SUGGESTS THIS MID-LEVEL VORT MAXIMA WILL
SLIDE ACROSS THE SOUTHERN APPALACHIANS LATE THIS AFTERNOON, AND THEN
OVER THE SOUTHERN PORTIONS OF OUR AREA EARLY THIS EVENING. GIVEN
THE RESIDUAL LOW-LEVEL MOISTURE IN PLACE AHEAD OF THE FRONT
(CONFIRMED BY THE 12Z KGSO SOUNDING), THERE STILL APPEARS A DECENT
CHANCE FOR ISOLATED TO SCATTERED SHOWERS TO DEVELOP LATE THIS
AFTERNOON AND EARLY THIS EVENING. LATEST CAMS ARE IN DECENT
AGREEMENT SPINNING MOST OF THIS ACTIVITY UP OVER OUR WESTERN AND FAR
SOUTHWESTERN PIEDMONT/SANDHILLS DURING THIS PERIOD (NON-ZERO CHANCE
SOMETHING REACHES THE TRIANGLE). OVERALL THOUGH, ANY QPF WITH THESE
SHOWERS SHOULD BE LIMITED TO GENERALLY A FEW HUNDREDS TO MAKE A FEW
TENTHS OF AN INCH AND NOT BE IMPACTFUL. IT IS WORTH NOTING, HOWEVER,
THAT FORECAST SOUNDINGS DO INDICATE THE POTENTIAL FOR STEEP LAPSE
RATES DURING THIS PERIOD (PARTICULARLY IN THE SOUTHERN
PIEDMONT/SANDHILLS). AS SUCH, WOULD NOT BE SURPRISED IF WE HAVE A
FEW STRIKES OF LIGHTNING WITH ANY "DEEPER" SHOWER.
HIGHS TODAY WILL MAX IN THE UPPER 40S TO LOWER 50S. OVERNIGHT LOWS
WILL DIP INTO THE LOWER 30S. EXPECT A PERIOD OF 15 TO 25 MPH GUSTS
BEHIND THE FRONT THIS EVENING, SUBSIDING SOME OVERNIGHT (BUT
REMAINING MIXED).
SHORT TERM /SATURDAY AND SATURDAY NIGHT/
AS OF 305 AM FRIDAY...
EXPECT FAIR AND FRIGID CONDITIONS TO START THE WEEKEND. THE AXIS OF
THE MEAN LONGWAVE TROUGH OVER E NOAM WILL BE SHIFTING TO OUR E SAT
MORNING, AND THE STOUT CYCLONIC NW STEERING FLOW WILL PROVIDE THE
IMPETUS FOR THE MUCH COLDER AIR MASS TO FINALLY SPILL PAST THE
HIGHER TERRAIN AND INTO CENTRAL NC. THE COLUMN WILL BE GENERALLY
QUITE DRY AND STABLE, FAVORING PLENTY OF SUNSHINE, ALTHOUGH WE MAY
SEE A FEW MID CLOUDS LATER IN THE DAY AS A WEAK SHEARED VORTICITY
LOBE DIVES INTO THE MEAN TROUGH BASE AND CROSSES THE CAROLINAS. LOW
LEVEL THICKNESSES ARE EXPECTED TO BE 20-25 M BELOW NORMAL SAT
MORNING, SO DESPITE THE INSOLATION AND DECENT MIXING, HIGHS SHOULD
ONLY BE IN THE 40S AREAWIDE. AFTER A MINOR UPTICK DURING THE DAY,
THICKNESSES THEN PLUMMET SAT NIGHT, TO THEIR EXPECTED LOWEST POINT
DURING THIS STRETCH, AROUND 1265-1275 M BY SUN MORNING, WITH VERY
LIGHT WINDS AND CLEAR SKIES FOSTERING GOOD RADIATIONAL COOLING.
EXPECT A WIDE RANGE OF LOWS, FROM THE MID TEENS TO MID 20S. -GIH
LONG TERM /SUNDAY THROUGH THURSDAY/
AS OF 205 AM FRIDAY...
COLD IS THE STORY FOR THE BEGINNING OF THE EXTENDED. WE HAVE
ADVERTISED THE PATTERN OVER THE LAST SEVERAL DAYS AND THAT HAS
LARGELY NOT CHANGED. AN ANOMALOUSLY STRONG 1040 MB ARCTIC HIGH OVER
THE LOWER GREAT LAKES SUN BUILDS INTO THE MID-ATLANTIC STATES BY 12Z
MON. THE ARCTIC AIR WILL BE WELL ENTRENCHED ACROSS THE REGION AT
THIS TIME WITH A CLASSICAL COLD AIR DAMMING PATTERN. HIGHS SUN ARE
EXPECTED TO BE SOME 12-16 DEGREES BELOW NORMAL IN THE UPPER 30S NE
TO LOW 40S SW. OPTIMAL RADIATIONAL COOLING WILL BE IN PLACE SUN
NIGHT AND 1000-925 MB THICKNESSES WILL BE AROUND 611 M. WITH THIS
AIRMASS, LOCAL RESEARCH SUPPORTS LOWS IN THE MID TEENS TO AROUND 20.
HIGHS ON MON WILL ONLY BE A DEGREE OR SO WARMER IN THE LOW TO MID
40S. THE CAD WEAKENS MON NIGHT AS THE HIGH MOVES OFF NEW ENGLAND,
BUT GOOD RADIATIONAL COOLING SHOULD STILL SUPPORT LOWS IN THE LOW TO
MID 20S.
A WARMING TREND IS EXPECTED TUE THROUGH THU WITH HIGHS GETTING
CLOSER TO AVERAGE IN THE LOW TO MIDDLE 50S, THOUGH HIGHS MAY BE
COOLER IN THE NW PIEDMONT IF A CAD REGIME RELOADS. ZONAL FLOW WILL
BE IN PLACE ALOFT MON AND TUE. COME WED AND THU, MODELS AND THEIR
RESPECTIVE ENSEMBLES STILL SHOW VARYING SOLUTIONS ON HOW A SOUTHERN
STREAM SHORTWAVE EVOLVES AS IT APPROACHES OUR AREA. THE SUITE OF
ENSEMBLE DATA FROM THE EPS/GEFS/GEPS WOULD SUGGEST BEST SHOWER
CHANCES LATE WED INTO MIDDAY THU, BUT A LOOK AT THE 00Z
DETERMINISTIC SOLUTIONS HAVE SLOWED THIS ONSET PERHAPS NOT UNTIL
THU. THE REASON FOR THIS IS THE MODELS ARE SHOWING A 1030+ MB HIGH
IN SOUTHERN QUEBEC/ONTARIO BUILDING BACK SOUTH, FAVORING A POSSIBLE
HYBRID CAD TO RETURN. CONFIDENCE IN RAIN CHANCES IS LOW TO SAY THE
LEAST, BUT FOR NOW HAVE FOCUSED POP CHANCES IN LINE WITH THE
ENSEMBLE CONSENSUS DISCUSSED EARLIER.
AVIATION /18Z FRIDAY THROUGH WEDNESDAY/
AS OF 1214 PM FRIDAY...
MVFR CEILINGS WILL HANG ON A BIT LONGER ESPECIALLY AT KFAY/KRWI, BUT
SHOULD LIFT THROUGH ~20Z EVERYWHERE. SCATTERED SHOWERS (AND PERHAPS
A ROGUE LIGHTNING STRIKE) REMAIN POSSIBLE LATE THIS AFTERNOON AND
EVENING, WITH BEST CHANCES AT KINT/KGSO/KFAY (BUT CAN'T RULE OUT A
SHOWER AT KRDU/KRWI AS WELL). ANY LINGERING SHOWERS SHOULD DISSIPATE
BY ~03Z. AN ARCTIC FRONT WILL CLEAR THE AREA TONIGHT, PROMOTING A
BRIEF PERIOD OF 20 TO 25 KT GUSTS WHICH SHOULD SUBSIDE SOME TONIGHT
(ALTHOUGH WINDS AT THE SFC WILL CONTINUE TO STIR SOME). ADDITIONAL
20 KT GUSTS WILL BE POSSIBLE SATURDAY AFTERNOON UNDER OTHERWISE VFR
CONDITIONS.
LOOKING BEYOND 18Z SAT, VFR CONDITIONS WILL PREVAIL THROUGH TUE
UNDER COLD HIGH PRESSURE. -GIH
RAH WATCHES/WARNINGS/ADVISORIES
NONE.
SYNOPSIS...HARTFIELD
NEAR TERM...LUCHETTI
SHORT TERM...HARTFIELD
LONG TERM...KREN
AVIATION...LUCHETTI/HARTFIELD
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