040
FXUS62 KGSP 190606
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
106 AM EST THU DEC 19 2024
SYNOPSIS
MUCH COOLER CONDITIONS ARE EXPECTED TO FILTER INTO OUR REGION TO
END THE WEEK. A NORTHWEST FLOW SNOW EVENT WILL PRODUCE LIGHT SNOW
ALONG THE TENNESSEE BORDER AREAS FROM LATE FRIDAY THROUGH SATURDAY
MORNING. THE COLDEST DAYS ARE EXPECTED TO BE SUNDAY AND MONDAY
THEN A LITTLE WARMER FOR CHRISTMAS.
NEAR TERM /THROUGH TODAY/
AS OF 1250 AM: WINDS HAVE NOW TURNED NW AT THE SFC ACROSS THE
NORTHWEST HALF OF THE CWA IN THE WAKE OF A COLD FRONT. A FEW
SPRINKLES OR ISOLATED SHOWERS REMAIN POSSIBLE ALONG THE FRONT,
MAINLY IN THE NC PIEDMONT, BUT THAT CHANCE WILL DIMINISH IN THE
NEXT COUPLE OF HOURS. WIDESPREAD STRATUS WEST OF THE APPALACHIANS
SUGGESTS A FEW SPRINKLES OR (WHERE COLD ENOUGH) RIME ICING MAY
DEVELOP ALONG THE TN BORDER THRU DAYBREAK. A FEW SITES GENERALLY
SOUTHEAST OF I-85 HAVE SEEN FOG OR LOW STRATUS DEVELOP, BUT THAT
IS EXPECTED TO ERODE WHEN THE FRONT ARRIVES--THE FRONT DOES APPEAR
TO HAVE LOST MOMENTUM NOCTURNALLY, SO IF CLEARING DOES NOT OCCUR
THERE IN THE NEXT COUPLE OF HOURS, THE FOG PROBABLY WILL LAST
THRU DAYBREAK. PATCHY VSBY OF 1/2 MILE OR LESS WILL OCCUR, AND
THIS CAN BE HANDLED WITH AN SPS WHICH WILL BE ISSUED SHORTLY.
A DEEP TROUGH WILL DIG INTO THE MIDWEST TODAY ASSOCIATED WITH A
STRONG CLIPPER LOW PRES SYSTEM. WEAK SFC HIGH PRES WILL CROSS THE
EASTERN GREAT LAKES, PROVIDING A WEAK WEDGE-LIKE PATTERN ACROSS
THE FA. LOW-LEVEL FLOW WILL BEGIN TO SHIFT OUT OF THE SW AGAIN BY
MIDDAY, WHICH LIKELY WILL INDUCE ENOUGH WARM UPGLIDE UNDER THE
INVERSION TO PERMIT PATCHY CLOUD COVER. THE COMBINATION OF NELY
SFC FLOW (AND IN SOME CASES CLOUDS) WILL RESULT IN HIGH TEMPS ABOUT
10-15 DEG COOLER THAN THURSDAY, BUT STILL A LITTLE ABOVE NORMAL.
SHORT TERM /TONIGHT THROUGH SATURDAY/
AS OF 200 PM EST WEDNESDAY: A RELATIVELY STRONG SHORT WAVE WILL DIVE
ACROSS THE AREA FRIDAY BRINGING AN ASSOCIATED ALBERTA CLIPPER
SURFACE LOW JUST NORTH OF THE AREA. THERE IS GOOD FORCING WITH THE
WAVE AND AN ASSOCIATED UPPER JET. THE RELATIVELY DEEP MOISTURE,
STRONG FORCING, AND DROPPING TEMPS WILL LEAD TO RAIN CHANGING TO
SNOW, MAINLY IN THE COUNTIES ALONG THE TN BORDER. THE SNOW CONTINUES
FRIDAY NIGHT INTO EARLY SATURDAY MORNING AS NW UPSLOPE FLOW REMAINS
OVER THE AREA. RIGHT NOW, IT LOOKS LIKE SNOW OF 1 TO 3 INCHES WILL
BE POSSIBLE ACROSS THE HIGHER ELEVATIONS WITH AROUND AN INCH OR SO
IN THE VALLEYS. A WINTER WEATHER ADVISORY MAY BE NEEDED ONCE THE
EVENT GETS CLOSER IN TIME. WINDY CONDITIONS ARE ALSO EXPECTED ACROSS
THE MOUNTAINS THROUGH THE PERIOD.
THE DEEPEST MOISTURE REMAINS ACROSS THE MOUNTAINS, BUT SOME WILL
SPILL OUT ACROSS THE FOOTHILLS AND I-77 CORRIDOR. EXPECT ISOLATED
SHOWERS OUTSIDE OF THE MOUNTAINS, BUT TEMPS AND DON'T FALL AS
QUICKLY THERE, SO JUST RAIN SHOWERS ARE EXPECTED. THAT SAID, IF THE
FREEZING LEVEL FALLS FAST ENOUGH OR THE WEAK INSTABILITY IS DEEP
ENOUGH, THEN GRAUPEL OR MIXED RAIN/SNOW IS POSSIBLE. NE GA AND MOST
OF THE UPSTATE REMAIN DRY, BUT SOME CLOUDS ARE POSSIBLE. BREEZY TO
WINDY CONDITIONS ARE EXPECTED.
THE PRESSURE GRADIENT ACROSS THE AREA RELAXES SATURDAY WITH SNOW
SHOWERS ENDING ACROSS THE MOUNTAINS AND WINDS DIMINISHING ACROSS THE
AREA. LOWS THURSDAY NIGHT WILL BE AROUND 5 DEGREES ABOVE NORMAL.
HIGHS FRIDAY WILL BE NEAR NORMAL BUT WITH AN EARLY HIGH ACROSS THE
HIGHER ELEVATIONS NEAR THE TN BORDER. LOWS FRIDAY NIGHT AROUND 5
DEGREES BELOW NORMAL. HIGHS SATURDAY AROUND 10 DEGREES BELOW NORMAL
AS A VERY COLD AIR MASS MOVES INTO THE AREA.
LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/
AS OF 230 PM EST WEDNESDAY: A WEAK SHORT WAVE DROPS INTO THE AREA
SUNDAY KEEPING THE DEEP TROUGH OVER THE AREA. HEIGHTS THEN RISE
SLOWLY THROUGH TUESDAY. HIGH PRESSURE BUILDS INTO THE AREA IN A COLD
AIR DAMMING CONFIGURATION SUNDAY AND REMAINS IN PLACE THROUGH
TUESDAY. THE AIR MASS IS STILL VERY COLD ON SUNDAY THEN SLOWLY
MODERATES BY TUESDAY. TEMPS WILL BE 10 TO 15 DEGREES BELOW NORMAL
THROUGH MONDAY RISING BUT STILL BELOW NORMAL TUESDAY. THE GUIDANCE
DIFFERS ON CHRISTMAS DAY WITH A LOW PRESSURE SYSTEM AND PRECIP
APPROACHING FROM THE WEST ON THE GFS AND CANADIAN. THE ECMWF IS
SLOWER WITH THE SYSTEM, KEEPING THE AREA DRY. HAVE FOLLOWED THE
GUIDANCE BLEND WHICH BRINGS A CHANCE OF RAIN INTO THE AREA DURING
THE DAY. SURFACE TEMPS COULD BE TRICKY, ESPECIALLY OF PRECIP STARTED
EARLY ENOUGH, MEANING A CHANCE OF FREEZING RAIN WITH A STRONG WARM
NOSE DEVELOPING. THAT SAID, THE OPERATIONAL AND ENSEMBLE GUIDANCE
INDICATE TEMPS WOULD BE WARM ENOUGH FOR ALL RAIN, SO WENT THAT WAY
AS WELL.
AVIATION /06Z THURSDAY THROUGH MONDAY/
AT KCLT AND ELSEWHERE: COLD FRONT APPEARS TO HAVE PUSHED PAST ALL
SITES EXCEPT KCLT AND POSSIBLY KAND, AS OF 0545Z. A FOG/STRATUS
LAYER DOES EXIST IN REMAINING SOUTHERLY FLOW REGIME AHEAD OF
THE FRONT, AND PER SATELLITE IS IMMEDIATELY SOUTH OF KCLT AND
HAD APPEARED TO BE ADVECTING NORTH. A TEMPO WAS INCLUDED THERE
MAINLY FOR THE CHANCE THIS LAYER REACHES THE FIELD BEFORE THE
FRONT INDUCES DRYING/MIXING; ADDITIONAL CHANCE OF -SHRA IS LIKELY
OF LITTLE CONSEQUENCE. WINDS WILL FLIP TO NW TO N FOLLOWING THE
FROPA AT ALL SITES, VEERING AROUND TO NE AFTER DAYBREAK; A FEW
GUSTS ARE LIKELY. AIRMASS BEHIND THE FRONT WILL BE SHALLOW; FRONT
STALLS JUST SOUTH OF THE TERMINAL AREA LATER TODAY. MOIST INVERSION
ONCE AGAIN MAY RESULT IN A PATCHY LOW VFR OR EVEN MVFR CLOUD DECK
SIMILAR TO THE PREVIOUS COUPLE OF AFTERNOONS. WARM UPGLIDE AT THE
TOP OF THE PBL WILL STRENGTHEN TONIGHT AS NEXT TROUGH APPROACHES
FROM THE WEST, AND THIS DEVELOPMENT LIKELY WILL REINSTATE MVFR
CIGS OVER MUCH OF THE AREA TONIGHT.
OUTLOOK: HIGH PRESSURE AND DRY CONDITIONS LAST THROUGH THE WEEKEND,
WITH THE EXCEPTION BEING A CHANCE FOR SNOW ALONG THE TN BORDER
FRI PM THRU SAT AM WITH A REINFORCING COLD FRONT. PERIODIC CIG
RESTRICTIONS CAN'T BE RULED OUT UNTIL THAT FRONT PASSES.
GSP WATCHES/WARNINGS/ADVISORIES
GA...NONE.
NC...NONE.
SC...NONE.
SYNOPSIS...DEO/WIMBERLEY
NEAR TERM...ARK/WIMBERLEY
SHORT TERM...RWH
LONG TERM...RWH
AVIATION...WIMBERLEY
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