897
FXUS62 KGSP 150817
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
317 AM EST SUN DEC 15 2024
SYNOPSIS
CHILLY, CLOUDY WEATHER IS IN STORE TODAY, WITH LIGHT FREEZING
RAIN LIKELY IN PARTS OF THE NORTH CAROLINA MOUNTAINS AND
FOOTHILLS. PRECIPITATION WILL TRANSITION TO ALL RAIN BY AFTERNOOON
AND END BY DAYBREAK MONDAY. TEMPERATURES TREND WARMER THROUGH THE
FIRST HALF OF THE WORK WEEK, WITH RAIN CHANCES BRIEFLY RETURNING
TO THE MOUNTAINS MONDAY NIGHT AND TO ALL LOCATIONS WEDNESDAY.
NEAR TERM /THROUGH TONIGHT/
AS OF 315 AM EST SUNDAY: LAPS/RTMA SURFACE WETBULB TEMP
OBSERVATIONS ARE SHOWING SIGNS OF WARMING AS THE PRECIP OVERCOMES
THE EVAPORATIONAL COOLING PROCESS AND PRECIP IS NOW REACHING THE
SURFACE. TEMPERATURES SHOULD CONTINUE TO FALL THROUGH DAYBREAK
AS WE ENTER THE COOLEST PART OF THE DIURNAL CYCLE AND SURFACE
TEMPERATURES MATCH CLOSER WITH WETBULB TEMPERATURES. WITH A LARGE
AND STRONG CP SURFACE HIGH (~1050MB) SET UP SHOP OVER SOUTHEASTERN
CANADA AND NEW ENGLAND, A CLASSICAL CAD REGIME HAS BECOME REALIZED
ACROSS THE CFWA AS ONGOING PRECIP HAS HELPED LOCK IN THE DOME OF
COLD AIR WITH AN EASTERLY LOW-LEVEL MOISTURE TRANSPORT OVERTOP THE
DOME. SURFACE WETBULB TEMPERATURES ARE STILL AT OR BELOW FREEZING IN
MOST LOCATIONS CURRENTLY HIGHLIGHTED UNDER A WINTER WEATHER ADVISORY
AND IS STILL ON TRACK FOR DECENT ICE ACCUMULATIONS. THIS INCLUDES
THE FAVORABLE EASTERN-FACING SLOPES ALONG THE BLUE RIDGE ESCARPMENT
AND HIGHER ELEVATIONS IN THE NORTHERN MOUNTAINS OF WESTERN NORTH
CAROLINA. VERTICAL PROFILES SHOW A PROMINENT WARM NOSE AT ALL
LOCATIONS EXPECTING WINTER WEATHER AND WILL KEEP P-TYPES MOSTLY
FREEZING RAIN IN THE FORECAST BEFORE ALL LOCATIONS TRANSITION TO
JUST LIQUID BY SUNDAY AFTERNOON. AN UPPER LEVEL LOW SHIFTS FROM THE
MID-MS VALLEY THROUGH THE UPPER GREAT LAKES DURING THE DAY AS THE
ATTENDANT FRONT WILL BRING IN CONTINUED SCATTERED SHOWERS THROUGH
00Z MONDAY BEFORE COVERAGE SLOWLY DWINDLES OVERNIGHT TONIGHT AS
THE BETTER FORCING FOR ASCENT ASSOCIATED WITH THE UPPER LOW LIFTS
TO THE NORTH. CAMS ARE ALSO MORE AGGRESSIVE WITH THE QPF RESPONSE
AND HAS LEAD TO A SLIGHT UPTICK IN ICE ACCUMULATIONS, BUT NOTHING
THAT SUGGEST AN UPGRADE TO ICE STORM WARNING IS NECESSARY AS THE
HEAVIEST POCKETS OF ICE WILL TOTAL BETWEEN 0.10"-0.25". HOWEVER,
WITH SLIGHTLY MORE COVERAGE IN FREEZING RAIN ACCUMULATIONS,
INCLUDED GREATER CALDWELL AND ALEXANDER COUNTIES TO A WINTER WEATHER
ADVISORY AS LIGHT ACCUMULATIONS ARE EVIDENT, BUT LESS THAN 0.10"
IS EXPECTED. TEMPERATURES WILL BE 10-15 DEGREES BELOW NORMAL FOR
AFTERNOON HIGHS TODAY AS WE REMAIN LOCKED INTO THE WEDGE ACROSS
MOST OF THE CFWA.
THE CLASSICAL CAD SETUP WILL SLOWLY COME TO AN END, BUT LIKELY TO
OCCUR IN THE SHORT-TERM AS THE DOME OF COLD AIR WILL BE TOUGH TO
ERODE AND THERE'S NOT A CLEAR MECHANISM FOR EROSION THROUGH THE
NEAR-TERM. MOST OF THE PRECIP WILL LIFT OUT OF THE AREA OVERNIGHT
TONIGHT AS THE UPPER LOW LIFTS INTO THE NORTHEASTERN CONUS AND
LOW-LEVEL WINDS VEER, WHILE SHORTWAVE RIDGING ALOFT BUILDS IN
FROM THE WEST. THE SURFACE HIGH REMAINS STRONG OFFSHORE THE NEW
ENGLAND COAST AND WILL CONTINUE TO NOSE IN A NORTHEASTERLY COMPONENT
THROUGH DAYBREAK TUESDAY, WHILE LOW CLOUDS REMAIN SOCKED IN OVER THE
CFWA. AS A RESULT, THE SENSIBLE WEATHER WILL DRY OUT BY THE END OF
THE FORECAST PERIOD, BUT OVERNIGHT LOWS WILL RUN 5-10 DEGREES ABOVE
NORMAL THANKS TO THE EXTENSIVE CLOUD COVER AND HIGHER HEIGHTS ALOFT.
SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/
AS OF 130 AM SUN: STILL LOOKING LIKE MOISTURE FLUX WILL DIMINISH
MONDAY SUPPORTING POPS BELOW SLIGHT-CHANCE, ALTHOUGH WARM
UPGLIDE WILL CONTINUE BELOW 850 MB, LIKELY MAINTAINING A FAIR
AMOUNT OF CLOUD COVER. PARENT HIGH FROM THE CAD EVENT WILL BE
CENTERED OFFSHORE, BUT MODELS CONTINUE TO DEPICT A LOBE OF THE
HIGH REMAINING OVER THE SOUTHEAST STATES UNDER A LOW-AMPLITUDE
UPPER RIDGE. GIVEN THE INITIAL STRENGTH OF CAD AND MOST HI-RES
GUIDANCE STILL DEPICTING AN INVERSION AND THE CLOUD COVER, STILL
SKEPTICAL WE'LL SEE AS BIG A WARM-UP AS E.G. THE NBM WOULD SUGGEST.
THAT IS TO SAY, THERE APPEARS BUST POTENTIAL ON MAX TEMPS.
NO BIG CHANGES TO THE EXPECTATIONS FOR THE NEXT FRONT, WHICH
STILL LOOKS TO CROSS THE LOWER OH/TN VALLEYS LATE MONDAY AND
EFFECTIVELY IMPINGE ON OUR MOUNTAINS BEFORE DAYBREAK TUESDAY. STILL
NOT EXPECTING THE FRONT TO HAVE GREAT DYNAMIC SUPPORT, WITH THE
DRIVING CYCLONE NORTH OF THE GREAT LAKES BY THE TIME THE FRONT NEARS
US. IT IS THUS PERHAPS NO SURPRISE THE SFC FRONT STALLS ACROSS TN
AND VA, AND IS NOT EXPECTED TO RESULT IN AIRMASS CHANGE FOR OUR
CWA. FURTHERMORE PRECIP PROBABLY WILL NOT HOLD TOGETHER PAST THE
MOUNTAINS, WITH THE ONLY FORCING BEING A WEAK CONVERGENCE ZONE AND
MOISTURE BEING EATEN UP AS WINDS TURN WESTERLY AND DOWNSLOPE. TOTAL
QPF WITH THE FRONT IS PROGGED TO BE LESS THAN A TENTH OF AN INCH
IN ALMOST ALL AREAS, WITH EVEN LOCATIONS NEAR THE MOUNTAIN SPINE
UNLIKELY TO SEE EVEN A QUARTER INCH. CONFIDENCE REMAINS HIGH THAT
TEMPS WILL BE CONSIDERABLY ABOVE FREEZING IN THE ENTIRE CWA WHEN
PRECIP CHANCES ARRIVE SO THIS OVERALL LOOKS LIKE A LOW-IMPACT FROPA.
THE DOWNSLOPING HOWEVER WILL ERODE ANY REMAINING VESTIGE OF CAD AND
SHOULD PROMOTE REMARKABLE WARMING ACROSS THE AREA DURING THE DAY;
FOR THE PIEDMONT WE STILL EXPECT UPPER 60S TO NEAR 70 FOR MAXES
TUE AFTN.
PRECIP CHANCES WILL LINGER LONGEST ALONG THE TN BORDER TUESDAY
BEFORE TAPERING OFF ONCE AGAIN IN THE EVENING; SOME CLOUD COVER MAY
DEVELOP EAST OF THE MOUNTAINS VIA THE CONVERGENCE ZONE. THE FRONTAL
ZONE WILL BE REACTIVATED TUE NIGHT AHEAD OF THE NEXT TROUGH AXIS
WHICH THEN WILL BE INVOF THE OZARKS. THE ECMWF IS MOST AGGRESSIVE
OF OUR DETERMINISTIC MODELS IN DEPICTING THE ACTIVATION, WITH
THE OTHER MAJOR DET MODELS BEING VIRTUALLY DRY. HOWEVER, ENSEMBLE
PROBS ARE ENOUGH TO JUSTIFY A SLIGHT-CHANCE MENTION IN OUR SOUTH
AND CHANCE ACROSS MOST OF WESTERN NC BY DAYBREAK WED. AGAIN,
ALL LIQUID AS MIN TEMPS REMAIN ABOVE NORMAL.
LONG TERM /WEDNESDAY THROUGH SATURDAY/
AS OF 200 AM SUN: THE REACTIVATING WARM FRONT IS SHOWN TO RETREAT
A LITTLE NORTHWARD ON WEDNESDAY AS TROUGH PUSHES EAST OF THE
MS RIVER AND A SFC LOW TRACKS UP THE OHIO VALLEY. MODELS HAVE
REMAINED PRETTY CONSISTENT OVER THE PAST FEW RUNS IN DEPICTING
THE DRIVING TROUGH HOLDING TOGETHER ACROSS THE INLAND EAST, AND
PROVIDING ENOUGH OOMPH TO BRING THE ASSOCIATED COLD FRONT ACROSS
THE SOUTHERN APPALACHIANS WEDNESDAY NIGHT. POPS RAMP UP UNTIL THE
FRONT PASSES, SUFFICIENT FOR A HIGH CHANCE TO LOW LIKELY MENTION
IN THE AFTERNOON AND EVENING. PWATS WILL DECLINE A BIT IN THE
WAKE OF THE WARM FRONT BUT STILL WILL BE UNSEASONABLY HIGH. MOST
MODELS ALSO DEPICT SMALL SBCAPE DEVELOPING DIURNALLY WITHIN THE
CWA, AND SUCH INSTABILITY LIKELY WOULD OVERLAP WITH 30+ KT OF
EFFECTIVE SHEAR. FLOW WILL BE UNIDIRECTIONAL AND PARALLEL TO THE
FRONT, WHICH WILL MITIGATE ANY RESULTING SEVERE THREAT. LOCALLY
HEAVY RAINFALL CAN'T BE RULED OUT ON ACCOUNT OF THE PWATS, BUT
OVERALL QPF IS NOT TERRIBLY REMARKABLE WITH ENSEMBLE PROBS NOT
INDICATIVE OF ANYTHING CLOSE TO A BROAD SCALE FLOOD THREAT. TEMPS
ON WED WILL BE SIMILARLY WARM TO TUESDAY'S, BUT FALL BEHIND THE
FRONT. A SMALL CHANCE OF NW FLOW SNOW EXISTS FOR THE MOUNTAINS
EARLY THURSDAY, BUT PRECIP STILL LOOKS TO END AS RAIN EVERYWHERE
ELSE THAT MORNING. TEMPS RETURN NEAR TO A LITTLE ABOVE NORMAL
THURSDAY AND SLIGHTLY BELOW NORMAL THURSDAY NIGHT AND FRIDAY,
AS STRONG HIGH PRESSURE MIGRATES ACROSS THE REGION FROM THE WEST.
MOST RUNS THEN DEPICT A SHORTWAVE ROUNDING THE RIDGE OVER THE
NORTHWEST COAST WEDNESDAY NIGHT AND TAKING A CLIPPER-LIKE TRACK
ACROSS THE CENTRAL/EASTERN CONUS, REACHING THE APPALACHIANS LATE
FRIDAY. THE CANADIAN GDPS IS THE MOST LIKE A TRUE ALBERTA CLIPPER,
FEATURING A COMPACT WAVE DIVING SOUTH TO NEAR OUR NORTHERN BORDER;
THE GFS AND ECMWF SOLUTIONS HAVE A LARGER SCALE TROUGH AND SFC
LOW BUT TAKE THE SYSTEM FARTHER NORTH SUCH THAT WE MAY NOT GET
MUCH DYNAMIC LIFT. ANOTHER COLD FRONT APPEARS LIKELY TO TRAIL THE
WAVE AND VIA THE INCOMING SUBARCTIC HIGH, TEMPS TREND BELOW NORMAL
FOR THE WEEKEND. POPS ARE NO BETTER THAN 20% ANYWHERE FRIDAY AND
FRIDAY NIGHT BUT COME AS A RESULT OF THIS WAVE AND THE MINOR NW
FLOW SNOW EVENT DEPICTED ALONG/BEHIND THE FRONT.
AVIATION /08Z SUNDAY THROUGH THURSDAY/
AT KCLT AND ELSEWHERE: CONDITIONS ARE DETERIORATING QUICKLY AS THE
MVFR LOW CLOUD DECK SPREADS ACROSS THE AREA AND LOCKS IN FOR MUCH
OF THE PERIOD. EXPECT SOME TERMINALS TO GRADUALLY LOWER TO IFR
BY DAYBREAK AND REMAIN THAT WAY THROUGH THE DAY, ESPECIALLY AT
THE UPSTATE TAF SITES AND KHKY/KAVL. KCLT WILL REMAIN LOW-END
MVFR THROUGH MOST OF THE DAY, BEFORE DROPPING TO IFR AFTER
00Z MONDAY. SCATTERED SHOWERS AND DRIZZLE WILL MOVE ACROSS
THE TERMINALS JUST BEFORE DAYBREAK AND REMAIN THAT WAY THROUGH
SUNSET BEFORE COVERAGE SLOWLY LESSENS. THERE ARE SOME HINTS THAT
TEMPERATURES COULD COOL ENOUGH FOR A BRIEF PERIOD OF FREEZING
RAIN AT KAVL AND INCLUDED THIS IN A TEMPO AROUND OR JUST BEFORE
DAYBREAK, BUT PRECIP WILL QUICKLY RETURN TO ALL LIQUID SOON AFTER
SUNRISE THIS MORNING. KCLT WILL STRUGGLE TO EEK OUT A FEW SHOWERS
UNTIL LATER IN THE AFTERNOON, BUT STILL KEPT A VCSH MENTION AS
A FEW PATCHES OF PRECIP SHOULD BREAK CONTAINMENT AND CROSSOVER
THE TERMINAL. WINDS WILL MAINTAIN A NORTHEASTERLY COMPONENT AT
ALL TAF SITES WITH LOW-END GUSTS THROUGH DAYBREAK AS THE PRESSURE
GRADIENT STAYS TIGHT AS THE DOME OF COLD AIR LOCKS IN. GUSTS WILL
GRADUALLY DROP OFF DURING THE DAY AND PREVAILING WINDS WILL DROP
UNDER 10 KTS AT ALL SITES BY THIS EVENING. KAVL WILL CONTINUE TO
TOGGLE OUT OF THE SOUTHEAST THROUGH THE FORECAST PERIOD.
OUTLOOK: RESTRICTIONS WILL CONTINUE MONDAY MORNING BUT EXPECT
GRADUAL LIFTING AS THE DAMMING CLEARS DURING THE DAY. UNSETTLED
PATTERN CONTINUES THROUGH THE REST OF THE WEEK AS MULTIPLE STORM
SYSTEMS PUSH INTO REGION LIKELY LEADING TO PERIODS OF ASSOCIATED
RESTRICTIONS.
GSP WATCHES/WARNINGS/ADVISORIES
GA...NONE.
NC...WINTER WEATHER ADVISORY UNTIL NOON EST TODAY FOR NCZ033-035-
049-050-053-064-065-501>503-505-507-509.
SC...NONE.
SYNOPSIS...WIMBERLEY
NEAR TERM...CAC
SHORT TERM...WIMBERLEY
LONG TERM...WIMBERLEY
AVIATION...CAC
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