385
FXUS62 KGSP 211727
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1227 PM EST SAT DEC 21 2024
SYNOPSIS
A NORTHWEST FLOW OF MOISTURE WILL PRODUCE LIGHT SNOW ALONG THE
TENNESSEE BORDER AREAS EARLY IN THE DAY, BUT THE MOISTURE SHOULD
PULL OUT BY EARLY AFTERNOON. MEANWHILE, COLD AIR WILL CONTINUE TO
FILTER INTO THE AREA. THE COLDEST DAYS ARE EXPECTED TO BE SUNDAY
AND MONDAY AS HIGH PRESSURE TAKES OVER. HOWEVER, TEMPERATURES ARE
EXPECTED TO TREND BACK TOWARD NORMAL FOR CHRISTMAS.
NEAR TERM /THROUGH TONIGHT/
AS OF 1152 AM EST SATURDAY: A LINGERING STRATOCU DECK IS OBSERVED
ALONG THE NC-TN BORDER, AND PERHAPS EVEN A FLURRY IS STILL
ONGOING SOMEWHERE, BUT BY AND LARGE IT'S QUIET ACROSS THE AREA.
WINDS HAVE TURNED NNW A LITTLE FASTER THAN EXPECTED, CUTTING OFF
GAP WINDS IN THE UPSTATE AND PREVENTING AS MUCH DOWNSLOPING FROM
TAKING PLACE ACROSS THE NC PIEDMONT. CONSEQUENTLY, IT'S A DEGREE
OR TWO CHILLIER THAN EXPECTED, AND THE FORECAST HAS BEEN ADJUSTED
ACCORDINGLY. THE UPPER TROUGH THAT DROVE LAST NIGHT'S MOUNTAIN
SNOW IS NOW ANALYZED JUST OFF THE ATLANTIC COAST, AND CANADIAN
HIGH PRESSURE IS SPILLING INTO THE FORECAST AREA BEHIND IT.
OTHERWISE...THERE'S A DECENT CHANCE THAT OUR NC PIEDMONT ZONES AND
POSSIBLY OUR UPSTATE ZONES COULD SEE ANOTHER BRIEF ROUND OF LOW-END
GUSTS THIS AFTERNOON AS AN EMBEDDED UPPER SHORTWAVE ROUNDS THE BASE
OF THE BROADER UPPER TROF RIGHT OVER OUR CWA THIS AFTERNOON. THESE
GUSTS SHOULD DISSIPATE BY LATE EVENING, THOUGH, WHEN THE FEATURE
TRANSLATES EAST OF THE AREA. HIGH TEMPS TODAY WILL BE ROUGHLY 5 TO
15 DEGREES BELOW NORMAL, WITH THE MTNS BEING THE MOST BELOW NORMAL.
SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/
AS OF 115 AM EST SATURDAY: THE SECOND HALF OF THE WEEKEND AND THE
START OF THE BRIEF WORK WEEK STILL LOOKS LIKE TYPICAL WINTER, AT
LEAST IN TERMS OF THE CHILLY TEMPS THAT WILL RUN ABOUT TEN DEGREES
BELOW NORMAL IN SPITE OF MOSTLY CLEAR SKY. THE CULPRIT WILL BE
A LARGE CONTINENTAL SFC HIGH THAT MOVES STEADILY FROM SW QUEBEC
ON SUNDAY, ACROSS UPSTATE NY AND NRN NEW ENGLAND SUNDAY NIGHT,
TO THE NEW ENGLAND COAST MONDAY, THEN OFFSHORE ON TUESDAY. THIS
HIGH WILL RIDGE DOWN THE EAST SIDE OF THE MTNS AND DOWN ACROSS
OUR REGION THROUGH MONDAY IN A COLD AIR DAMMING CONFIGURATION,
BUT WITH A SIGNIFICANT LACK OF MOISTURE, YOU WILL SCARCELY NOTICE
IT OTHER THAN THE COLD NORTHEASTERLY BREEZE. THINGS GET A LITTLE
INTERESTING, MAYBE, ON MONDAY NIGHT AS THE GFS DEVELOPS A WAVE
ON THE OLD ARCTIC FRONT OFF THE SOUTHEAST COAST AND SPREADS SOME
MOISTURE NORTHWARD TOWARD THE WESTERN PIEDMONT. BY THAT TIME, A
NRN STREAM WAVE WILL CUT US OFF FROM THE PARENT HIGH OFFSHORE AND
LEAVE BEHIND A WEAK HIGH OVER THE MTNS, KEEPING LOW TEMPS BELOW
FREEZING. HOWEVER, THE GEFS DOESN'T SHOW MUCH SUPPORT AND THE
OTHER OPERATIONAL RUNS ARE DRY. SO, WE WILL KEEP THE COOL TEMPS,
LESS CLOUD COVER, AND NO PRECIP IN THE FORECAST, RATHER THAN THE
PROBLEMATIC LIGHT PRECIP OF THE OPERATIONAL GFS.
LONG TERM /TUESDAY THROUGH SATURDAY/
AS OF 231 AM EST SATURDAY: THE REST OF THE FORECAST PERIOD CONTINUES
TO LOOK LIKE A LOW-CONFIDENCE AFFAIR, AS A DEVELOPING BLOCKING
PATTERN SEEMS TO BE GIVING FITS TO THE MODELS. IF THERE IS ANY
CONSISTENCY, IT WOULD BE THAT SOME WEAK CONSENSUS THAT AFTER A
NRN STREAM WAVE MOVES PAST, WE SLIP RIGHT BACK INTO A COLD AIR
DAMMING REGIME ON TUESDAY AS A MEAN MID/UPPER RIDGE AXIS SETS UP
OVER THE EAST COAST AND PERSISTS FOR THE REST OF THE WEEK. THIS
ACTS TO DEFLECT A SERIES OF DAMPENING SHORT WAVES PAST TO OUR NW,
ONE PERHAPS ON WEDNESDAY AND THE NEXT PERHAPS FRIDAY, LEAVING
US WITH ONLY WEAK FORCING AND MOISTURE, SUGGESTING THAT ANY
SIGNIFICANT WEATHER WILL BE SOMEWHERE OTHER THAN HERE. THE MODEL
BLEND RESULTS IN PRECIP CHANCES CREEPING UP INTO THE CHANCE RANGE,
IN DEFERENCE TO THE WETTER SOLUTIONS INCLUDING THE CANADIAN, BUT THE
PROBS ARE LIMITED TO THE 30-40 PERCENT RANGE AT BEST. FORTUNATELY,
THE SITUATION SUPPORTS TEMPS RUNNING SLIGHTLY ABOVE NORMAL, SO ANY
PRECIP IS MOST LIKELY TO BE RAIN, WITH THE EXCEPTION OF PERHAPS
THE MTN PEAKS ABOVE 6K FEET WHICH WOULD HAVE THE POTENTIAL FOR
SOME WET SNOW AT TIMES. HOPEFULLY THE NEXT FEW DAYS WILL PROVIDE
SOME MUCH NEEDED CLARITY.
AVIATION /18Z 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...PM
NEAR TERM...JPT/MPR
SHORT TERM...PM
LONG TERM...PM
AVIATION...MPR
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