438
FXUS62 KRAH 200705
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
205 AM EST FRI DEC 20 2024
SYNOPSIS
AN ARCTIC COLD FRONT AND STRONG UPPER LEVEL DISTURBANCE WILL
APPROACH FROM THE WEST EARLY THIS MORNING AND CROSS THE AREA TODAY
THROUGH TONIGHT. THIS WILL BRING MUCH COLDER AIR INTO THE REGION FOR
THE WEEKEND.
NEAR TERM /THROUGH TONIGHT/
AS OF 815 PM THURSDAY...
WEAK SOUTHERLY OVERRUNNING AND ISENTROPIC LIFT ATOP A WEDGE OF COOL
HIGH PRESSURE EXTENDING SOUTH DOWN THE ATLANTIC SEABOARD IS
SUPPORTING WIDESPREAD STRATUS WITH CLOUD BASES RUNNING BETWEEN 2-
5KFT ACROSS THE AREA. UPPER LEVEL FORCING OVERSPREADING THE AREA
DURING THE LATTER HALF OF THE NIGHT, VIA INCREASING UPPER JET
DIVERGENCE AND 80-140M H5 HEIGHT FALLS DUE TO THE ARRIVAL OF A
STRENGTHENING UPPER PV ANOMALY INTO THE SOUTHERN AND CENTRAL
APPALACHIANS WILL AIDE IN THE DEVELOPMENT OF LIGHT PATCHY RAIN AND
DRIZZLE. BEST CHANCES SEEM TO BE ALONG AND EAST OF US-1.
OVERNIGHT LOWS RANGING FROM MID 30S ALONG THE VA BORDER TO AROUND
40 ACROSS THE SOUTHERN COUNTIES.
SHORT TERM /FRIDAY AND FRIDAY NIGHT/
AS OF 225 PM THURSDAY...
A DEEPENING UPPER LEVEL TROUGH WILL SWING ACROSS OUR REGION FRIDAY
BEFORE CLEARING THE REGION EARLY SATURDAY MORNING. AT THE SURFACE, A
LOW PRESSURE OFFSHORE WILL SKIRT UP THE MID-ATLANTIC COAST THROUGH
THE DAY BRINGING SCATTERED SHOWERS AND A FEW ISOLATED STORMS THE
COASTAL PLAIN AND SANDHILLS REGION, EARLY FRIDAY. TO THE WEST,
ANOTHER SURFACE LOW CENTERED OVER THE OH VALLEY IS EXPECTED TO TREK
SOUTHEAST TOWARDS THE APPALACHIAN MOUNTAINS ALONG WITH A A TRAILING
COLD FRONT. THE LOW WILL MOVE TO THE NORTHEAST, AND THE COLD FRONT
WILL MOVE ACROSS THE REGION FRIDAY BRINGING SCATTERED SHOWERS AND
ISOLATED STORMS. ALL PRECIP SHOULD CLEAR OUT OF THE REGION BY THE
EVENING HOURS AS THE COLD AIR RUSHES IN BEHIND THE PRECIP. A FEW
GUSTS ARE POSSIBLE AS THE COLD FRONT MOVES OVER THE REGION AS WELL.
FRIDAY HIGH TEMPERATURES WILL BE BELOW AVERAGE RANGING FROM UPPER
40S TO LOW 50S. LOWS WILL GENERAL BE IN THE LOW TO MID 30S WITH A
FEW COOLER SPOTS IN THE UPPER 20S.
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 /06Z FRIDAY THROUGH TUESDAY/
AS OF 1245 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 08Z-13Z MAINLY 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 18Z. BROKEN BANDS OF LIGHT SHOWERS ARE EXPECTED TO CROSS THE
AREA, MAINLY LATE MORNING THROUGH EARLY AFTERNOON, THEN AGAIN FROM
LATE AFTERNOON THROUGH THE EVENING, WITH MOSTLY MVFR CIGS THROUGH
THE REST OF THE TAF VALID PERIOD. SURFACE WINDS WILL BE GENERALLY
LIGHT AND VARIABLE UNDER 6 KT, BUT LATE IN THE PERIOD (AFTER 01Z)
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 06Z SAT, MVFR CIGS MAY LINGER FOR A FEW MORE HOURS IN
THE EAST, BUT AFTER 09Z ALL TERMINALS SHOULD HAVE BECOME VFR WITH
CLEARING SKIES AND A BREEZE FROM THE NW. VFR CONDITIONS WILL
PREVAIL THROUGH TUE UNDER COLD HIGH PRESSURE. -GIH
RAH WATCHES/WARNINGS/ADVISORIES
NONE.
SYNOPSIS...HARTFIELD
NEAR TERM...CBL
SHORT TERM...CA
LONG TERM...KREN
AVIATION...HARTFIELD
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