394
FXUS62 KRAH 201124
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
625 AM 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 240 AM FRIDAY...
WE'VE GOT A FEW ROUNDS OF PRECIP POTENTIAL TO CONTEND WITH TODAY
INTO TONIGHT, ALTHOUGH ANY PRECIP WILL BE LIGHT WITH SCATTERED
COVERAGE AT MOST.
THE LATEST SURFACE ANALYSIS SHOWS US WITHIN A VERY WEAK/BAGGY MSLP
PATTERN, WITH VERY WEAK HIGH PRESSURE OVER THE AREA BETWEEN A
SURFACE LOW JUST OFFSHORE AND ANOTHER SURFACE LOW OVER THE OHIO
VALLEY. THE LATTER IS ATTACHED TO A POTENT MID LEVEL SHORTWAVE
TROUGH THAT WE'VE BEEN ANTICIPATING FOR THE LAST FEW DAYS, AND AS
THIS WAVE APPROACHES AND PASSES OVERHEAD THIS MORNING INTO TONIGHT,
WE'LL SEE A FEW OPPORTUNITIES FOR ISOLATED TO SCATTERED LIGHT
SHOWERS. FIRST, WITH LOW LEVEL NE FLOW INTO NE NC AROUND THE
OFFSHORE LOW, AND WITH AREA SURFACE OBSERVATIONS, UA SOUNDINGS, AND
ACARS SOUNDINGS SHOWING A NEARLY SATURATED LAYER FROM ~1500 FT TO
~5000 FT AGL OVER THE CWA UNDERGOING WEAK MOIST UPGLIDE, SOME PATCHY
LIGHT DRIZZLE IS POSSIBLE IN OUR NE SECTIONS THROUGH DAYBREAK. THEN,
WE'LL SEE THE FIRST OF TWO VORTICITY LOBES SWINGING THROUGH THE
REGION, ASSOCIATED WITH THE AFOREMENTIONED INCOMING SHORTWAVE
TROUGH, THIS MORNING. THIS WEAKER LEAD WAVE IS NOTED ON GOES LAYER
WV IMAGERY MOVING THROUGH THE OHIO VALLEY TO MIDDLE TN AND MAY
GENERATE A BRIEF UPTICK IN COLUMN LIFT TO SUPPORT A BROKEN BAND OF
ISOLATED TO SCATTERED LIGHT SHOWERS THIS MORNING. THIS FORCING FOR
ASCENT WILL INCLUDE AN UPPER DIVERGENCE MAX IN THE RIGHT ENTRANCE
REGION OF A 100 KT JET STREAK. MOST CAMS DEPICT VERY SPOTTY COVERAGE
AT ANY GIVEN TIME, INCLUDING IN AGGREGATE AS THE HREF SHOWS AT LEAST
20-40% PROBABILITY OF MEASURABLE PRECIP THIS MORNING MAINLY ACROSS
OUR S HALF, IN LINE WITH LARGER SCALE MODEL OUTPUT. AGAIN, THOUGH,
WITH THE LACK OF ANY GULF OR ATLANTIC MOISTURE INFLUX AND THE LACK
OF ANY ICE IN THE CLOUDS, ANY PRECIP THIS MORNING IS APT TO BE
PROGRESSIVE AND THUS VERY BRIEF AND LIGHT. FINALLY, LATER IN THE
DAY, THE STRONGER PV MAX NOTED CURRENTLY ON WV IMAGERY OVER S MN/E
IA WILL STREAM ACROSS THE CAROLINAS, MOST LIKELY BETWEEN 21Z AND
04Z. MOST MODELS HAVE BEEN CONSISTENT IN DROPPING LIGHT PRECIP WITH
SCATTERED COVERAGE OVER OUR AREA (WITH SLIGHTLY BETTER COVERAGE S
THAN N) DURING THIS TIME WINDOW. AND MODELS CONTINUE TO INDICATE A
TROPOPAUSE FOLD OVER THE CAROLINAS WITH THE 2 PVU SURFACE REACHING
DOWN TO 600-700 MB AND A CORRESPONDING INCREASE IN LAPSE RATES
THROUGH A DEEP LAYER TO AROUND 7.5 C/KM AND A LOWERING OF SURFACE
PRESSURES OVER OUR S SECTIONS. AS NOTED PREVIOUSLY, WHILE THE
PROJECTED ELEVATED/SHALLOW CAPE IS QUITE SMALL, GIVEN THE STRONG
FORCING FOR ASCENT GENERATED BY THE PV MAX AND THE ANTICIPATED
MOISTENING UP INTO THE MIXED PHASE REGION ALOFT, I WOULD NOT BE
SURPRISED TO SEE A FEW LIGHTNING STRIKES LATE AFTERNOON INTO EARLY
EVENING. EXPECT HIGHS TODAY FROM THE MID-UPPER 40S NE TO THE MID 50S
S, WITH A FEW PERIODS OF PARTIAL SUNSHINE BUT OVERALL CONSIDERABLE
CLOUDINESS. THE ARCTIC SURFACE FRONT WILL CLOSELY TRAIL THE
SHORTWAVE TROUGH, DRIVING THROUGH OUR AREA THIS EVENING INTO THE
OVERNIGHT AND BRINGING CLEARING SKIES. A BRIEF PERIOD OF GUSTY WINDS
IS EXPECTED JUST BEHIND THE FRONT, MOST NOTABLY OVER THE PIEDMONT.
WILL HAVE LOWS JUST A BIT BELOW NORMAL, MOSTLY 30-35 WITH A FEW
UPPER 20S, AS IT WILL TAKE SOME TIME FOR THE COLDEST AIR TO BREACH
THE MOUNTAINS AND WORK INTO OUR AREA. -GIH
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 /12Z FRIDAY THROUGH TUESDAY/
AS OF 625 AM FRIDAY...
CONFIDENCE IS HIGH THAT MVFR CONDITIONS WILL DOMINATE CENTRAL NC
TERMINALS THROUGH MID MORNING, A RESULT OF HIGH MOISTURE AND VERY
LIGHT WINDS THROUGH THE LOWEST 3-4 KFT. PATCHY DRIZZLE IS ALSO
POSSIBLE THROUGH 14Z AT EASTERN TERMINALS, BUT VSBYS SHOULD REMAIN
VFR REGARDLESS. STARTING MID MORNING, AS A SERIES OF UPPER LEVEL
DISTURBANCES CROSSES THE AREA AHEAD OF AN ARCTIC COLD FRONT, CIGS
WILL BE MOSTLY MVFR, BUT CIGS MAY BRIEFLY POP UP TO VFR BETWEEN 14Z
AND 19Z. BROKEN BANDS OF LIGHT SHOWERS ARE EXPECTED TO CROSS THE
AREA, MAINLY THIS MORNING, THEN AGAIN FROM LATE AFTERNOON THROUGH
THE EVENING, WITH MOSTLY MVFR CIGS UNTIL SHORTLY AFTER MIDNIGHT,
AFTER WHICH TIME SKIES WILL CLEAR OUT TO VFR. SURFACE WINDS WILL BE
GENERALLY LIGHT AND VARIABLE UNDER 6 KT, BUT FOR A FEW HOURS THIS
EVENING, WINDS AT INT/GSO WILL INCREASE TO 10-15 KT GUSTING TO 15-20
KTS FROM THE NW AS THE SURFACE COLD FRONT MOVES IN.
LOOKING BEYOND 12Z SAT, VFR CONDITIONS WILL PREVAIL THROUGH TUE
UNDER COLD HIGH PRESSURE. -GIH
RAH WATCHES/WARNINGS/ADVISORIES
NONE.
SYNOPSIS...HARTFIELD
NEAR TERM...HARTFIELD
SHORT TERM...HARTFIELD
LONG TERM...KREN
AVIATION...HARTFIELD
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