685
FXUS62 KGSP 151638
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1138 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 AFTERNOON 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 BY WEDNESDAY.
NEAR TERM /THROUGH TONIGHT/
AS OF 1040 AM EST SUNDAY: TEMPS HAVE WARMED ACROSS THE AREA TO THE
POINT WHERE ONLY AVERY COUNTY NC AND A FEW ISOLATED SPOTS NEAR THE
BLUE RIDGE ESCARPMENT NORTH OF I-40 ARE NEAR FREEZING, SO MOST OF
THE WINTER WEATHER ADVISORY CAN BE LET GO A BIT EARLY. WILL CONTINUE
TO EVALUATE AVERY OVER THE NEXT HOUR TO SEE IF A SHORT EXTENSION
WOULD BE IN ORDER. OTHERWISE, PRECIP CHANCES WERE TWEAKED BASED
ON RADAR TRENDS, WHICH DIDN'T CHANGE THE FORECAST AS MUCH AS THE
TEMP CHANGES DID. FOR THE AFTERNOON, A CLASSIC COLD AIR DAMMING
WEDGE WILL PERSIST THANKS TO A LARGE 1050MB SFC HIGH ANCHORED OVER
THE ST LAWRENCE VALLEY AND ONGOING LIGHT PRECIP, WITH MORE MOVING
IN FROM THE WEST. THAT WILL KEEP TEMPS DOWN ABOUT 10-15 DEGREES
BELOW NORMAL.
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 /18Z SUNDAY THROUGH FRIDAY/
AT KCLT AND ELSEWHERE: CONDITIONS DETERIORATED QUICKLY AS THE
MVFR/IFR LOW CLOUD DECK IS LOCKED 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. 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 NCZ033-049-
050-501-503-505.
SC...NONE.
SYNOPSIS...WIMBERLEY
NEAR TERM...CAC/PM
SHORT TERM...WIMBERLEY
LONG TERM...WIMBERLEY
AVIATION...CAC
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