310
FXUS62 KGSP 212301
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
601 PM EST SAT DEC 21 2024
SYNOPSIS
COLD AIR WILL CONTINUE TO FILTER INTO THE AREA OVER THE NEXT COUPLE
OF DAYS HIGH PRESSURE REMAINS IN CONTROL OF THE AREA. HOWEVER,
TEMPERATURES ARE EXPECTED TO TREND BACK TOWARD NORMAL FOR CHRISTMAS
WITH MORE MOISTURE RETURNING TO THE AREA AS WELL.
NEAR TERM /THROUGH SUNDAY/
AS OF 545 PM EST SATURDAY: NO MAJOR CHANGES NEEDED WITH THIS
UPDATE. CLOUDS CONTINUE TO BANK UP AGAINST THE WESTERN SLOPES OF
THE NC MOUNTAINS, WHILE WINDS ARE LOSING THEIR GUSTINESS ACROSS
THE AREA. TEMPS ARE ON TRACK.
OTHERWISE...DEEP LAYER N/NW FLOW SHOULD PERSIST THROUGH THE BULK
OF THE PERIOD. WE'RE ALREADY PAST THE HEIGHT OF CAA, AND THAT'S
REFLECTED IN THE DOWNWARD TREND WITH RESPECT TO GUSTS ACROSS THE
PIEDMONT AND UPSTATE. BROAD TROUGHING IS STILL IN PLACE ACROSS
THE EASTERN SEABOARD, BUT HEIGHTS WILL INCREASE SUBTLY NOW THAT
THE CENTRAL TROUGH AXIS IS EAST OF US. MOST GUIDANCE NOW DEPICTS
A WEAK SHORTWAVE PIVOTING ACROSS THE SOUTHERN BLUE RIDGE AND INTO
THE UPSTATE THIS EVENING, BUT IT SHOULDN'T AMOUNT TO MUCH MORE
THAN PERHAPS SOME THIN CLOUDS OVER THE UPSTATE THE FIRST PART
OF TONIGHT. THESE WILL DISPERSE ONCE THE SHORTWAVE SLIDES EAST
OF THE AREA AFTER MIDNIGHT...AND MOST LOCATIONS WILL SEE LOWS
IN THE LOWER 20S TONIGHT. THAT WILL MAKE FOR A VERY COLD NIGHT,
ESPECIALLY WITH WINDS NEVER QUITE DYING DOWN (IN FACT, IT LOOKS
LIKE BASED ON MODEL SOUNDINGS, THE BOUNDARY LAYER WILL NEVER QUITE
DECOUPLE THROUGH SUNRISE). SO, WE'LL BE STARTING OUT COLD ON SUNDAY
MORNING, AND HIGHS TOMORROW ARE EXPECTED TO BE A CATEGORY COLDER
THAN TODAY'S, DESPITE CLEAR SKIES AND CONTINUING HIGH PRESSURE.
RHS ARE EXPECTED TO FALL INTO THE 30-35% RANGE TOMORROW AFTERNOON,
BUT BY THE TIME THIS OCCURS, WINDS SHOULD HAVE DROPPED OFF ENOUGH
TO AVERT ANY SERIOUS FIRE WEATHER CONCERNS.
SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/
AS OF 145 PM EST SATURDAY: DEEP UPPER TROUGH AXIS WILL BE PUSHING
OFF THE EASTERN SEABOARD AS WE MOVE INTO THE SHORT TERM, AND
CONFLUENT FLOW ALOFT UPSTREAM OF THE TROUGH WILL ALLOW THE COLD
SURFACE HIGH TO SLIDE OVER THE APPALACHIANS AND WEDGE DOWN THE
EASTERN SLOPES SUNDAY NIGHT, CONTINUING THE WELL-BELOW-NORMAL
TEMPERATURES ON MONDAY. NO MOISTURE ATTENDANT WITH THE CAD SO JUST A
COLD DRY DAY. THE PATTERN FLATTENS BRIEFLY DURING THE DAY AS A
SHORTWAVE DIGS IN TO THE UPPER MIDWEST, INDUCING WEAK DOWNSTREAM
RIDGING OVER THE APPALACHIANS. GFS WANTS TO DEVELOP A COASTAL WAVE
MONDAY NIGHT AND ECMWF IS A LITTLE WEAKER WITH THIS FEATURE, BUT
BOTH ARE INDICATING AN INCREASE IN CLOUD COVER TOWARDS THE END OF
THE SHORT TERM. SHOULD HAVE A MUCH WARMER DAY ON TUESDAY WITH FLOW
FLATTENING ALOFT AS THE SURFACE HIGH SHIFTS OFFSHORE BRINGING FLOW
BACK FROM THE SOUTH.
LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/
AS OF 215 PM EST SATURDAY: THE MIDWEST SHORTWAVE WILL WORK ITS WAY
EAST AS WE MOVE INTO THE EXTENDED, WITH A SOUTHERN STREAM SHORTWAVE
DIGGING INTO THE SOUTHERN PLAINS, AND A WEAK FRONT EXTENDING BETWEEN
THE TWO. VERY LITTLE DEEP MOISTURE ASSOCIATED WITH THIS SYSTEM AND
GEFS SOLUTIONS SEEM TO AGREE, NEVERTHELESS ENOUGH GENERAL SUPPORT
FOR SOME LOW-END POPS LATE CHRISTMAS DAY INTO THURSDAY. ANOTHER
SHORTWAVE EJECTING OUT OF THE SOUTHERN PLAINS TOWARD THE END OF THE
PERIOD MIGHT BE SLIGHTLY MORE INTERESTING ESPECIALLY WITH ANOTHER
SURFACE DAMMING HIGH IN PLACE OVER THE AREA, THOUGH TEMPERATURES
WILL NOT BE PARTICULARLY COLD AND MID-LEVEL RIDGING WILL KEEP THE
BEST OF THE MOISTURE DEFLECTED TO OUR NW. POPS INCREASE TOWARD THE
END OF THE PERIOD INTO THE MID- TO HIGH-CHANCE RANGE. TEMPERATURES
THROUGH THE PERIOD REMAIN ABOVE FREEZING FOR ALL BUT THE HIGHEST
PEAKS SO NO REAL P-TYPE ISSUES TO SPEAK OF.
AVIATION /23Z SATURDAY THROUGH THURSDAY/
AT KCLT AND ELSEWHERE: A VFR 18Z TAF PERIOD IS EXPECTED, AS
CANADIAN HIGH PRESSURE SPILLS INTO THE TERMINAL FORECAST AREA
BEHIND A DEPARTING UPPER DISTURBANCE. LINGERING STRATOCU OVER
THE NC MOUNTAINS LOOKS LIKE IT'S GOING TO CLEAR IMMINENTLY, BUT
INCLUDED A ONE-HOUR TEMPO FOR MVFR CEILINGS AT KAVL JUST IN CASE;
OTHERWISE, ALL THE SITES CAN EXPECT VFR CONDITIONS THROUGH THE END
OF TOMORROW. EXPECT SPORADIC GUSTS VIRTUALLY EVERYWHERE THROUGH
LATE THIS AFTERNOON, THOUGH THEY'LL BE PATHETIC COMPARED TO WHAT
MANY LOCATIONS SAW YESTERDAY EVENING AND OVERNIGHT. GUSTS SHOULD
SUBSIDE AFTER SUNSET TODAY.
A SECOND WEAK UPPER DISTURBANCE WILL PIVOT ACROSS THE SOUTHERN BLUE
RIDGE AND SC UPSTATE QUICKLY THIS EVENING, DEPARTING BEFORE MIDNIGHT
BUT POTENTIALLY STIRRING UP SOME FEW/SCT LOW-VFR CLOUDS OVER THE
UPSTATE TERMINALS LATE THIS AFTERNOON UNTIL A LITTLE AFTER DARK.
WILL THEY BE OPERATIONALLY SIGNIFICANT? ALMOST CERTAINLY NOT.
WHATEVER THIN CLOUDS DO DEVELOP BECAUSE OF THIS FEATURE WILL
DISPERSE AFTER MIDNIGHT, GIVING WAY TO SKC FOR THE REMAINDER OF
THE PERIOD. WINDS, CURRENTLY N, WILL GRADUALLY BECOME MORE NE
TOMORROW, WITH A PERIOD OF VRB WINDS EXPECTED LATE IN THE DAY
SUNDAY AS THE CENTER OF HIGH PRESSURE ARRIVES IN THE CAROLINAS.
OUTLOOK: EXPECT BROAD HIGH PRESSURE AND MOSTLY DRY CONDITIONS TO
PERSIST THRU EARLY NEXT WEEK. PRECIPITATION CHANCES AND ASSOCIATED
RESTRICTIONS INCREASE BY MID-WEEK.
GSP WATCHES/WARNINGS/ADVISORIES
GA...NONE.
NC...NONE.
SC...NONE.
SYNOPSIS...TDP
NEAR TERM...ARK/MPR
SHORT TERM...TDP
LONG TERM...TDP
AVIATION...MPR
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