870
FXUS62 KGSP 160845
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
345 AM EST SUN FEB 16 2025
SYNOPSIS
A COLD FRONT CROSSES THE AREA TODAY WITH SHOWERS AND PERHAPS
ISOLATED THUNDERSTORMS. BRISK WINDS DEVELOP QUICKLY BEHIND THE
FRONT THIS MORNING AND CONTINUE INTO TONIGHT. DRY HIGH PRESSURE
BUILDS IN MONDAY AND LINGERS THROUGH TUESDAY. ANOTHER LOW PRESSURE
SYSTEM CROSSES THE AREA WEDNESDAY, BRINGING A CHANCE FOR WINTRY
WEATHER. COLD AND DRY HIGH PRESSURE RETURN LATE NEXT WEEK.
NEAR TERM /THROUGH TONIGHT/
KEY MESSAGES:
1) AREAS OF DENSE FOG CONTINUES ACROSS MUCH OF THE PIEDMONT, AND
A DENSE FOG ADVISORY REMAINS IN EFFECT THROUGH 5 AM THIS MORNING.
2) WIND ADVISORY FOR THE ENTIRE CWA IN EFFECT FROM EARLY MORNING
THROUGH THE AFTERNOON FOR GUSTY WINDS OF 30-40 MPH EAST OF THE
MOUNTAINS AND 45+ MPH IN THE MOUNTAINS THROUGH EARLY MONDAY MORNING.
3) A COLD FRONT BRINGS LINE OF SHOWERS AND THUNDERSTORMS ACROSS THE
FORECAST AREA THIS MORNING, WITH A NON-ZERO THREAT OF SEVERE STORMS.
4) NW FLOW SNOW SHOWERS ALONG THE TN/NC BORDER BEHIND THE FRONT
THIS AFTERNOON THROUGH TONIGHT WITH LIGHT ACCUMULATIONS.
AS OF 330 AM EST SUNDAY: A WEAKENING QLCS CONTINUES TO TRACK
ACROSS EASTERN TN AND INTO NE GA. IT IS ESTIMATED TO ARRIVE IN THE
SMOKIES AROUND 4:30 AM. THE LINE IS OUTRUNNING MOST OF ITS SFC-BASED
INSTABILITY, BUT WITH A COUPLE HUNDRED J/KG OF MUCAPE, THE LINE WILL
LIKELY BE ABLE TO CROSS THE FORECAST AREA. WITH THE LIMITED
INSTABILITY AND THE LINE HAVING TO WORK OVER A RESIDUAL WEDGE, NOT
EXPECTING MUCH OF A SEVERE THREAT, ALTHOUGH ISOLATED DAMAGING WIND
GUSTS CANNOT BE RULED OUT. LOW-LEVEL SHEAR ALONG THE WEDGE BOUNDARY
COULD PRESENT A NON-ZERO TORNADO THREAT ACROSS THE LOWER PIEDMONT
AND EAST IN THE CHARLOTTE AREA AFTER DAYBREAK. THE 00Z HREF SHOWS A
FEW WEAK UPDRAFT HELICITY STREAKS IN OUR FAR SOUTHERN ZONES.
MEANWHILE, AS THE WEDGE ERODES, WIDESPREAD FOG WITH AREAS OF 1/4SM
VSBY CONTINUE ACROSS THE PIEDMONT. THE VSBY SHOULD IMPROVE QUICKLY
AS THE LINE OF CONVECTION AND ASSOCIATED COLD FRONT ROLLS THRU AND
INCREASES MIXING. THE DENSE FOG ADVISORY MAY NEED TO BE EXTENDED
BEYOND 5 AM FOR AN HOUR OR TWO FOR PARTS OF THE FORECAST AREA.
BY LATE MORNING, THE CONVECTION AND COLD FRONT WILL PUSH EAST OF
THE AREA, AND GUSTY WEST TO SOUTHWEST WINDS WILL RAMP UP ACROSS THE
ENTIRE AREA. WITH 30-40 KT ATOP THE MIXED LAYER, THE WIND ADVISORY
LOOKS GOOD. CLOUDS WILL START TO CLEAR OUT, EXCEPT LINGERING
ALONG THE TN BORDER DUE TO WESTERLY TO WEST-NORTHWESTERLY UPSLOPE
FLOW. GUIDANCE IS IN GOOD AGREEMENT ON UPSLOPE SHOWERS TURNING
FROM RAIN TO SNOW FAIRLY QUICKLY THIS AFTN, BUT SNOW ACCUMS ARE
EXPECTED TO BE LIGHT AND MAINLY ON THE HIGHEST PEAKS. TEMPS WILL
BE TRICKY AS THEY START OUT SO WARM IN THE HIGH TERRAIN, WHILE THE
COLD WEDGE AIR MASS WILL BE SCOURED OUT BY DOWNSLOPE FLOW, THEN
STRONG CAA. DEFINITELY EXPECT FALLING TEMPS ACROSS THE MOUNTAINS
THRU THE DAY, WHILE THERE IS BUST POTENTIAL ON WHETHER TEMPS WILL
BE ABLE TO GET INTO THE 60S EAST OF THE MOUNTAINS, AS THE NBM SHOWS.
WINDS SHOULD START TO DECREASE, BUT MAY REMAIN BREEZY THRU
THE EVENING EAST OF THE MOUNTAINS, WHILE WINDS MAY INCREASE
FURTHER ACROSS THE HIGHER TERRAIN, ESPECIALLY IN THE NORTHERN
MOUNTAINS. SO THE WIND ADVISORY CONTINUES IN THE MOUNTAINS THRU
MONDAY MORNING. MEANWHILE, SNOW SHOWER ACTIVITY LOOKS TO PEAK EARLY
IN THE EVENING, THEN GRADUALLY TAPER OFF OVERNIGHT. STORM TOTAL
SNOW AMOUNTS ARE HIGHLY ELEVATION DEPENDENT AND GENERALLY 1-2"
ALONG THE TN BORDER, WHICH IS SHY OF ADVISORY CRITERIA. TEMPS
WILL FALL TONIGHT INTO THE TEENS TO LOW 20S IN THE MOUNTAINS AND
IN THE MID TO UPPER 20S ELSEWHERE.
SHORT TERM /MONDAY THROUGH WEDNESDAY NIGHT/
AS OF 245 AM EST SUNDAY: THE SHORT TERM WILL BEGIN WITH COOL HIGH
PRESSURE BUILDING IN TO THE AREA UNDER STRONG WESTERLY/ZONAL FLOW
ALOFT, PROBABLY STILL SOME MOUNTAIN WAVE ACTIVITY LEADING TO SOME
GUSTS MIXING DOWN IN THE MOUNTAINS AS WE START THE PERIOD. HIGHS
MONDAY AND LOWS MONDAY NIGHT 5 OR SO DEGREES BELOW SEASONAL NORMALS.
WILL SEE SOME MODIFICATION TO THE AIRMASS ON TUESDAY AS THE FLOW
ALOFT SHIFT SLIGHTLY MORE OUT OF THE WSW, WITH HIGHS TUESDAY MUCH
CLOSER TO SEASONAL NORMALS.
MEANWHILE, A TROUGH WILL BEGIN TO DIG OUT OF THE ROCKIES ON TUESDAY
FROM A PARENT CUTTING OFF IN THE NORTHERN PLAINS BY TUESDAY NIGHT.
WEAK SOUTHERN STREAM SHORTWAVE TRAVERSING NORTHERN GULF COAST
UNDERNEATH RIGHT ENTRANCE REGION OF THE STRONG UPPER JET HELPS TO
INDUCE SURFACE CYCLOGENESIS THAT TRAVERSES THE GULF COAST TUESDAY
NIGHT INTO WEDNESDAY IN A BEAUTIFUL MILLER-A SETUP. VERY STRONG
(1050MB) ARCTIC HIGH PRESSURE OVER THE NORTHERN PLAINS WILL
PRIMARILY RIDGE SOUTH BUT AN ARM OF RIDGING WILL STRETCH EAST AND
THEN DOWN THE EASTERN SEABOARD. AS MOISTURE FROM THE GULF LOW STARTS
SPREADING NORTH, INSITU DAMMING WILL REINFORCE THE RIDGING. ALL THIS
LEADS TO A VERY COMPLICATED WINTRY PRECIP EVENT WEDNESDAY INTO
WEDNESDAY NIGHT.
ENSEMBLE GUIDANCE AS WELL AS OPERATIONAL MODELS ARE POINTING TO A
MAINLY SNOW EVENT FOR THE NORTHERN TIER OF COUNTIES, BUT
UNSURPRISINGLY UNCERTAINTY COMES INTO PLAY THE FARTHER SOUTH WE GO.
THERE IS SOME QUESTION AS TO THE DEPTH OF MOISTURE AS WELL AS
PRESENCE/EXTENT OF WARM NOSE WITH CAA ALOFT AROUND THE 850MB WESTERN
ATLANTIC ANTICYCLONE. WITH THIS CURRENT PACKAGE, TEMPERATURE
PROFILES SEEM TO INDICATE THAT THE HIGHEST LIKELIHOOD OF FREEZING
RAIN OR PERHAPS SLEET WOULD BE WEDNESDAY NIGHT INTO EARLY THURSDAY
AS WE LOSE ICE NUCLEI. DIFFERENT GUIDANCE BRINGS SNOW TOTALS FARTHER
SOUTH; E.G., ECMWF MORE BULLISH WITH SNOW AMOUNTS, GFS IS MORE LIKE
WHAT SNOW? (EXCEPT FOR THE NC MOUNTAINS OF COURSE). ENSEMBLE MEMBERS
OF EACH ARE SLIGHTLY DIFFERENT BUT IN GENERAL THERE DOES SEEM TO BE
A DIVIDING LINE AROUND THE NC/SC STATE LINE. UNCERTAINTY OF COURSE
REMAINS QUITE HIGH ON EXTENT OF ACCUMULATING SNOW, AMOUNTS, HOW MUCH
ICE MAY (OR MAY NOT) MIX IN. MILLER-A TYPE SYSTEMS ARE TYPICALLY
LESS LIKELY TO HAVE "MIXED BAG" P-TYPES WITH THE LOCATION OF THE LOW
ACROSS THE COAST, SO TAKING PATTERN RECOGNITION INTO ACCOUNT VS PURE
MODEL OUTPUT, WILL BE INTERESTING TO SEE HOW THE FORECAST EVOLVES AS
WE GET CLOSER.
FOR NOW, TEMPERATURES WEDNESDAY ARE FORECAST TO BE MID 30S IN THE
MOUNTAINS AND I-40 CORRIDOR TO LOWER 40S SOUTH, BUT THIS MAY BE TOO
HIGH. WELL BELOW NORMAL FOR WEDNESDAY NIGHT AND WITH WINDS PICKING
UP, WIND CHILLS IN THE HIGHER ELEVATIONS WILL BE DIPPING BELOW 0
TOWARDS DAYBREAK AS THE FRONT PUSHES THROUGH.
LONG TERM /THURSDAY THROUGH SATURDAY/
AS OF 315 AM EST SUNDAY: EXTENDED STARTS OFF UNSEASONABLY COLD AND
BREEZY ON THURSDAY IN THE WAKE OF THE WINTER WEATHER EVENT. THE
UPPER LOW WILL BE PASSING JUST TO OUR NORTH ACROSS THE MID-ATLANTIC
STATES AND STRONG UPPER GRADIENT WILL LEAD TO CONTINUED MOUNTAIN
WAVE ACTIVITY AND GUSTY WINDS THROUGH THE DAY. CONTINUED
UNSEASONABLY COLD THROUGH THE REST OF THE PERIOD WITH ONLY SLIGHT
MODIFICATION TO HIGHS.
ANOTHER SHORTWAVE MOVING THROUGH ON SATURDAY MAY BRING SOME WINTRY
PRECIP TO THE MOUNTAINS AND COLD RAIN TO SOUTHERN ZONES, BUT A BIT
TOO FAR OUT TO NARROW DOWN DETAILS ON THIS.
AVIATION /09Z SUNDAY THROUGH THURSDAY/
AT KCLT AND ELSEWHERE: A MESSY SET OF TAFS, WITH LIFR TO VLIFR CIGS
AND VSBY EXPECTED ACROSS THE PIEDMONT UNTIL A LINE OF SHRA/TSRA
CROSS THE AREA EARLY THIS MORNING FROM WEST TO EAST. THE LINE
IS EXPECTED TO WEAKEN AS IT ENTERS THE AREA, BUT MAY PRODUCE
GUSTY/ERRATIC WINDS AND BRIEF DOWNPOURS. THE LINE IS BEING HANDLED
WITH TEMPO GROUPS, AS CONFIDENCE IN TIMING INCREASES. VERY STRONG
SW WINDS ATOP AN ERODING WEDGE WILL LIKELY RESULT IN NON-CONVECTIVE
LLWS AT ALL SITES, UNTIL THE CONVECTION ARRIVES. THEN GUSTY SW
WINDS EXPECTED IN WAKE OF A PASSING COLD FRONT. GUSTS MAY BE
STRONG, WITH FREQUENT GUSTS OVER 30 KT FROM LATE MORNING THRU
THE AFTN. CIGS AND VSBY SHOULD IMPROVE THIS MORNING, WITH SKIES
CLEARING OUT IN THE AFTN. WINDS WILL BEGIN TO WEAKEN THIS EVENING,
BUT MAY REMAIN GUSTY. AT KAVL, SW WIND WILL BRIEFLY BE OUT OF THE
W, THEN TOGGLE TO NNW UP THE VALLEY BY MID-AFTN, REMAINING VERY
GUSTY THRU THE EVENING.
OUTLOOK: VFR CONDITIONS EXPECTED MONDAY THRU TUESDAY. THEN A
QUICK-MOVING STORM SYSTEM MAY BRING WINTRY PRECIP AND RESTRICTIONS
TO THE REGION ON WEDNESDAY.
GSP WATCHES/WARNINGS/ADVISORIES
GA...DENSE FOG ADVISORY UNTIL 5 AM EST EARLY THIS MORNING FOR
GAZ010-017-018-026-028-029.
WIND ADVISORY UNTIL 6 PM EST THIS EVENING FOR GAZ010-017-018-
026-028-029.
NC...DENSE FOG ADVISORY UNTIL 5 AM EST EARLY THIS MORNING FOR
NCZ035>037-056-057-068>072-082-502-504-506-508-510.
WIND ADVISORY UNTIL 6 PM EST THIS EVENING FOR NCZ035>037-056-
057-068>072-082-502-504-506-508-510.
WIND ADVISORY UNTIL NOON EST MONDAY FOR NCZ033-048>053-058-059-
062>065-501-503-505-507-509.
SC...DENSE FOG ADVISORY UNTIL 5 AM EST EARLY THIS MORNING FOR
SCZ008>014-019-101>109.
WIND ADVISORY UNTIL 6 PM EST THIS EVENING FOR SCZ008>014-019-
101>109.
SYNOPSIS...ARK
NEAR TERM...ARK
SHORT TERM...TDP
LONG TERM...TDP
AVIATION...ARK
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