381
FXUS62 KGSP 191935
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
235 PM 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 FRIDAY/
AS OF 230 PM: A VIGOROUS CLIPPER SYSTEM CONTINUES TO TRACK ACROSS
THE UPPER MIDWEST, WHILE AXIS OF WEAK HIGH PRES SLIDES ACROSS THE
APPALACHIANS. THE HIGH WILL PRODUCE A WEDGE-LIKE PATTERN OVER THE
FORECAST AREA TONIGHT INTO FRIDAY, WITH MOIST ISENTROPIC LIFT
PRODUCING LAYERS OF STRATUS ACROSS MOST OF THE AREA. THE LIFT
MAY BE ENOUGH FOR SPOTTY SPRINKLES. BUT MEASURABLE PRECIP LOOKS
UNLIKELY. TEMPS WILL BE ABOUT 5-8 DEGREES ABOVE NORMAL.
FRIDAY, THE VIGOROUS SHORTWAVE ASSOCIATED WITH THE CLIPPER WILL
DIVE THRU THE OHIO VALLEY, RESULTING IN STRONG UPPER FORCING ACROSS
THE FORECAST AREA. FLOW WILL TURN OUT OF THE WEST, THEN NORTHWEST
DURING THE DAY, SCOURING OUT THE STRATUS. TEMPS ARE EXPECTED TO
GET INTO THE MID 50S WITH HELP FROM DOWNSLOPE WARMING AND CLEARING
SKIES. THIS COMBINED WITH STEEPENING MID-LEVEL LAPSE RATES WITH THE
PASSING SHORTWAVE WILL YIELD SOME SBCAPE EAST OF THE MOUNTAINS. MOST
GUIDANCE AGREES ON ISOLATED TO SCATTERED SHOWERS DEVELOPING IN THE
NC PIEDMONT IN THE AFTN, QUICKLY TRACKING EAST-SOUTHEAST BY EARLY
EVENING. INSTABILITY WILL PROBABLY NOT BE ENOUGH FOR ANY THUNDER,
BUT FORECAST SOUNDINGS SUGGEST CANNOT RULE OUT GRAUPEL/SMALL HAIL
IN THE DEEPEST CONVECTION. MEANWHILE, 850 MB TEMPS WILL PLUMMET
ACROSS THE MOUNTAINS, WITH NW FLOW UPSLOPE SHOWERS RAMPING UP ALONG
THE TN BORDER. SFC TEMPS WILL START OUT ABOVE FREEZING IN THE HIGH
TERRAIN, BUT THE HIGHEST PEAKS COULD SEE SOME ACCUMULATING SNOW
BEFORE SUNSET, ESPECIALLY IN THE SMOKIES WHERE THE COLD AIR WILL
ARRIVE FIRST.
SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/
AS OF 210 PM EST THURSDAY: A NORTHWEST FLOW SNOW EVENT WILL BE FULLY
ONGOING ACROSS THE USUAL LOCATIONS FRIDAY NIGHT BEHIND THE DEPARTING
ALBERTA CLIPPER SURFACE LOW. EXPEC SNOW CHANCES TO SLOWLY DIMINISH
OVERNIGHT BUT LINGER INTO SATURDAY MORNING BEFORE ENDING BY
AFTERNOON. ALL ELEMENTS ARE THERE FOR ACCUMULATING SNOWFALL TO
CONTINUE ACROSS MAINLY THE HIGHER ELEVATIONS, BUT SOME LIGHT
ACCUMULATIONS WILL OCCUR IN THE NW TO SE ORIENTED VALLEYS AS WELL.
STORM TOTALS LOOK TO BE 1 TO 4 INCHES WITH LOCALLY HIGHER AMOUNTS
ACROSS THE HIGHER ELEVATIONS. LOWER ELEVATIONS COULD SEE UP TO
AROUND AN INCH. A WINTER WEATHER ADVISORY MAY BE NEEDED BY THE TIME
THE EVENT ARRIVES. VERY GUSTY CONDITIONS ARE ALSO EXPECTED.
OUTSIDE OF THE MOUNTAINS CLOUDS WILL SCATTER OUT FRIDAY EVENING BUT
BREEZY TO WINDY CONDITIONS CONTINUE.
CLEAR SKIES AND LIGHTER WINDS ARE EXPECTED FOR EVERYONE SATURDAY
NIGHT AND SUNDAY. THE COLD AIR BEGINS FILTERING IN FRIDAY NIGHT AND
SATURDAY. LOWS WILL BE AROUND 5 DEGREES BELOW NORMAL WITH HIGHS 5 TO
10 DEGREES BELOW NORMAL. THE COLD AIR MASS FULLY SETTLES IN SATURDAY
NIGHT AND SUNDAY WITH TEMPS 10 TO 15 DEGREES BELOW NORMAL.
LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/
AS OF 150 PM EST THURSDAY: GUIDANCE STILL UNCERTAIN ABOUT THE PRECIP
CHANCES THROUGH THE PERIOD, BUT THEY DO AGREE THAT IF THERE IS
PRECIP, IT SHOULD ALL BE LIQUID. AN UPPER RIDGE STARTS OUT OVER THE
AREA MONDAY, THEN FLATTENS AS A SHORT WAVE PASSES BY TO OUR NORTH ON
TUESDAY. THE RIDGE RETURNS FOR CHRISTMAS DAY AS SHORT WAVES DIG INTO
THE CENTRAL CONUS. THE GFS BRINGS ONE OF THE SHORT WAVES ACROSS THE
AREA EARLY THURSDAY. THE ECMWF DOESN'T PHASE THE SHORT WAVES TAKING
ONE WELL NORTH OF THE AREA CHRISTMAS NIGHT THEN REBUILDING THE RIDGE
THURSDAY AS ANOTHER SHORT WAVE DIVES INTO THE SOUTHERN PLAINS. THE
CANADIAN IS MORE SIMILAR TO THE GFS BUT STRONGER AND FASTER WITH THE
LATE PERIOD SHORT WAVE. AT THE SURFACE, THEY AGREE ON A HIGH
PRESSURE IN CAD CONFIGURATION FOR MONDAY. THE SHORT WAVE PASSING
NORTH OF THE AREA TUESDAY SPLITS THE HIGH WITH A WEAK FRONT DROPPING
TOWARD THE AREA BUT HIGH PRESSURE CENTERED OVER US. THE FRONT STALLS
TO OUR NORTH CHRISTMAS DAY. THEN THE GFS BRINGS MOISTURE AND PRECIP
IN THURSDAY WITH LOW PRESSURE MOVING INTO THE OH VALLEY AND FORMING
ALONG THE CAROLINA COAST. THE CANADIAN SHOWS THIS AS WELL BUT BUT
BRINGS PRECIP IN AS EARLY AS LATE CHRISTMAS EVE AND CONTINUING
THROUGH THURSDAY MORNING. THE ECMWF HOLDS OFF ON ANY SIGNIFICANT
PRECIP UNTIL LATE THURSDAY AT THE EARLIEST. THE GFS AND CANADIAN
ENSEMBLE MEANS ARE ALSO WETTER, BUT WARM ENOUGH FOR ANY PRECIP TO BE
LIQUID. THE PREVIOUS RUN OF THE ECMWF ENSEMBLE MEAN AS ALSO WET BUT
WARM. THAT'S A LOT OF WORDS TO SAY THERE IS QUITE A BIT OF
UNCERTAINTY IN THE FORECAST. THEREFORE, WENT CLOSE TO THE GUIDANCE
BLEND WHICH HAS A DRY MONDAY AND TUESDAY AND CHANCE POPS CHRISTMAS
DAY AND THURSDAY. IT ALSO HAS TEMPS MONDAY WELL BELOW NORMAL WITH A
WARMING TREND THROUGH THE PERIOD WITH TEMPS RISING TO NEAR NORMAL
FOR CHRISTMAS DAY AND ABOVE NORMAL ON THURSDAY. AS MENTIONED ABOVE,
THIS KEEPS ALL PRECIP LIQUID FOR NOW.
AVIATION /20Z THURSDAY THROUGH TUESDAY/
AT KCLT AND ELSEWHERE: A MOIST EASTERLY TO SOUTHEASTERLY FLOW
IS EXPECTED TO PRODUCE A GRADUAL INCREASE IN LOW CIGS ACROSS
THE TERMINAL FORECAST AREA THIS AFTN THRU TONIGHT. CONFIDENCE IS
BELOW AVERAGE ON THE EXACT TIMING OF MVFR TO POSSIBLY IFR CIGS,
BUT CONFIDENCE IS HIGH THAT RESTRICTIVE CIGS WILL IMPACT ALL SITES
AT SOME POINT TONIGHT THRU FRIDAY MORNING. WINDS ARE EXPECTED TO
GO LIGHT THIS EVENING, BUT THE AIR MASS UNDER THE CLOUD DECK MAY
BE TOO DRY FOR FOG. CANNOT RULE OUT SOME PATCHY FOG, ESPECIALLY
NEAR THE ESCARPMENT. THE STRATUS SHOULD START TO LIFT/SCATTER
OUT AROUND MIDDAY FRIDAY, AS A COLD FRONT PUSHES INTO THE AREA
FROM THE NORTHWEST. THE FRONT WILL TOGGLE WINDS OUT OF THE WSW
TO WNW BY EARLY AFTN. AT CLT...GUIDANCE IS IN GOOD AGREEMENT ON
SCATTERED SHOWERS FORMING IN THE NW PIEDMONT. SO WILL ADD A PROB30
FOR SOME SHRA.
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
NEAR TERM...ARK
SHORT TERM...RWH
LONG TERM...RWH
AVIATION...ARK
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