426
FXUS62 KGSP 181745
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1245 PM EST TUE FEB 18 2025
SYNOPSIS
DRY HIGH PRESSURE LINGERS OVER THE REGION TODAY. WINTRY WEATHER
IS LIKELY FOR PARTS OF THE AREA ON WEDNESDAY AS A FAST-MOVING LOW
PRESSURE SYSTEM PASSES ACROSS THE SOUTHEAST. DRY HIGH PRESSURE
RETURNS THURSDAY BRINGING VERY COLD WEATHER TO END THE WEEK.
NEAR TERM /THROUGH TONIGHT/
AS OF 1230 PM: STILL THINKING DRY WEATHER WILL PERSIST ACROSS THE
AREA THROUGH AT LEAST DAYBREAK, WITH ONLY A SMALL CHANCE OF LIGHT
SNOW DEVELOPING IN OUR FAR WESTERN MOUNTAINS BY THAT TIME. THE 12Z
GUIDANCE SEEN SO FAR LARGELY IS IN LINE WITH THE PREVIOUS FORECAST,
A NOTABLE EXCEPTION BEING THE NAM WHICH HAS TRENDED COLDER AND
WETTER FOR A TIME WED MORNING, LEADING IT TO SHIFT SOME SN/PL TO
FZRA IN ITS P-TYPE OUTPUT, AND THUS DEPICTS APPRECIABLY HIGHER ICE
ACCUMS IN THE TRANSITION ZONE (GENERALLY NEAR THE NC/SC BORDER EAST
OF I-26). THE OFFICIAL FORECAST FOR P-TYPE TRENDS OR ACCUMS HAS
NOT BEEN CHANGED YET; WIND/SKY/VSBY HAVE BEEN UPDATED FOR AVIATION
PACKAGE. WILL BEGIN UPDATES TO THE REST OF THE FORECAST NOW.
WEAK SHORT WAVES APPROACH FROM THE WEST OVERNIGHT IN THE ZONAL FLOW
ACROSS THE AREA. THERE WILL BE AN INCREASE IN MID LEVEL MOISTURE
WITH THE WAVES. LOW LEVEL MOISTURE ALSO INCREASES TOWARD MORNING AS
ISENTROPIC LIFT BEGINS. STILL, NEITHER THE SYNOPTIC NOR ISENTROPIC
LIFT WILL BE STRONG ENOUGH FOR SIGNIFICANT PRECIP CHANCES FOR
MOST OF THE AREA UNTIL AFTER DAYBREAK. CHANCES RAMP UP EARLY IN
THE NEXT PERIOD. LOWS WILL BE UP TO 5 DEGREES BELOW NORMAL.
SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/
AS OF 330 AM TUESDAY: STILL ON TRACK FOR A QUICK WINTRY WX EVENT
FOR MUCH OF THE FORECAST AREA WEDNESDAY INTO EARLY THURSDAY. LATEST
GUIDANCE HAS SIMILAR QPF TO PREVIOUS FCST CYCLE, SO CONFIDENCE
IS INCREASING IN AN ADVISORY-LEVEL EVENT FOR MUCH OF OUR NC
ZONES. CONFIDENCE REMAINS LOWER FOR OUR SC AND GA ZONES, DUE TO
MORE MARGINAL TEMPS FOR SNOW, SLEET, OR ICE ACCUMS.
AN UPPER SHORTWAVE TROUGH WILL EJECT OUT OF THE SOUTHERN PLAINS
AND PROVIDE STRONG DPVA OVER THE FORECAST AREA DURING THE DAY
WEDNESDAY. AT THE SFC, A SPRAWLING ARCTIC HIGH WILL BEGIN TO NUDGE
INTO THE MID-ATLANTIC, HELPING SUPPLY COLD AIR TO OUR REGION WITH A
HYBRID CAD SETUP. SFC LOW PRES WAVE WILL TRACK ALONG THE GULF COAST,
WITH ISENTROPIC LIFT AHEAD OF THE LOW SPREADING MOISTURE NORTH
OVER THE COLD AIR MASS. SOME OF THE GUIDANCE, LIKE THE HRRR, SHOW
A PRONOUNCED GAP IN THE DEEPER MOISTURE BETWEEN ATLANTIC MOISTURE
TO OUR EAST AND THE GULF MOISTURE TO OUR WEST. THIS RESULTS IN A
RELATIVE MINIMUM OF QPF RIGHT OVER THE CWFA. THE LATEST QPF REALLY
LOOKS TOO LOW FOR WARNING-CRITERIA SNOW OR ICE ACCUMS. ADD TO THE
UNCERTAINTY IS THERMAL PROFILES. THICKNESSES SHOULD SUPPORT MAINLY
ALL SNOW ACROSS THE MOUNTAINS AND MOST OF THE NC PIEDMONT, SO 1-2"
OF SNOW ACCUMS LOOKS LIKELY IN THESE AREAS. AFTER COORDINATING WITH
NEIGHBORING OFFICES, HAVE OPTED TO ISSUE A WINTER WEATHER ADVISORY
FOR ALL OUR NC ZONES AND ALSO RABUN COUNTY, GA. THE PRECIP BREAKING
OUT AROUND DAYBREAK WEDNESDAY WILL FALL MAINLY ON ROADS THAT ARE
ABOVE FREEZING. SO HOPEFULLY THAT WILL LIMIT IMPACTS. BUT AS THE LOW
TRACKS BY TO OUR SOUTH, THERE IS SOME POTENTIAL FOR FRONTOGENETICAL
BANDING THAT COULD LOCALLY ENHANCE SNOW RATES. CONFIDENCE ON WHERE
THAT HAPPENS REMAINS LOW. FOR OUR SC AND GA ZONES, A TRANSITION
ZONE OF RA/SN AND POTENTIALLY SOME IP/FZRA MAY SET UP, BUT LOOKS
LIKE IT WILL BE NARROW. MINOR SNOW ACCUMS MAY BE POSSIBLE ACROSS
THE NORTHERN UPSTATE AND YORK/CHESTER. BUT THAT SNOW SHOULD BE
MOSTLY ON GRASSY SURFACES AND AT THE MOMENT IS TOO LOW TO WARRANT
AN ADVISORY. TEMPS WILL HOVER NEAR FREEZING WHERE THE SNOW FALLS,
WITH HIGHS MAINLY IN THE 30S TO LOWER 40S.
COLD AIR SHOULD START TO FILTER IN WEDNESDAY EVENING, FREEZING
ROADS, WHILE PRECIP SHOULD BEGIN TO TAPER OFF FROM WEST TO
EAST. SNOW SHOWERS WILL LINGER ACROSS THE MOUNTAINS, AS MOIST
NWLY UPSLOPE FLOW RAMPS UP. THE GFS HAS A BAND OF SNOW FORM
ACROSS THE I-77 CORRIDOR THURSDAY MORNING, PERHAPS DUE TO ANOTHER
BAND OF FRONTOGENESIS AS THE SFC LOW DEEPENS AND MOVES INTO THE
ATLANTIC. BUT MOST OTHER GUIDANCE DOES NOT HAVE THIS. MINOR
ADDITIONAL SNOW ACCUMS MAY BE POSSIBLE, ESPECIALLY IN THE
MOUNTAINS. THIS COMBINED WITH THE COLD ROADS SEEMS TO WARRANT
HAVING THE WINTER WX ADVISORY GO THRU THURSDAY MORNING. NW FLOW
SNOW SHOWERS WILL LIKELY CONTINUE INTO THURSDAY AFTN, BUT THE REST
OF THE AREA SHOULD SEE CLEARING SKIES. GUSTY NW WINDS IS EXPECTED
ACROSS THE ENTIRE FORECAST AREA, BUT NOT EXPECTED TO REACH ADVISORY
CRITERIA, EXCEPT FOR THE HIGHEST PEAKS. HIGHS WILL BE 15-20 DEG
BELOW NORMAL WITH WIND CHILLS MAKING IT FEEL EVEN COLDER.
NW FLOW SNOW SHOWERS ARE EXPECTED TO TAPER OFF BY EARLY THURSDAY
EVENING, BUT NW WINDS WILL LINGER THRU THE NIGHT. THURSDAY LOOKS
TO BE THE COLDEST NIGHT OF THE WEEK, WITH LOWS IN THE SINGLE
DIGITS ACROSS MOST OF THE HIGH ELEVATIONS ABOVE 3500 FT, AND
TEENS ELSEWHERE. WIND CHILLS MAY DROP BELOW -5 IN THE NORTHERN NC
MOUNTAINS, POSSIBLY WARRANTING A COLD WEATHER ADVISORY.
LONG TERM /FRIDAY THROUGH TUESDAY/
AS OF 100 AM TUESDAY: ARCTIC HIGH PRESSURE WILL SETTLE OVER THE
SOUTHEAST FRIDAY THRU SATURDAY, WITH DRY CONDITIONS EXPECTED. AS
THE AIR MASS MODERATES, TEMPS WILL START A WARMING TREND FROM
FRIDAY MORNING'S CHILLY START. HIGHS SHOULD REBOUND A FEW DEGREES
FROM THURSDAY'S READINGS, BUT STILL ABOUT 10 DEG BELOW NORMAL, THEN
JUST A FEW DEG BELOW NORMAL SATURDAY. A SHORTWAVE TROUGH WILL DIVE
SOUTHEAST ACROSS THE ROCKIES AND INTO THE SOUTHERN PLAINS, THEN
FLATTEN OUT AS IT MOVES INTO QUASI-ZONAL FLOW ACROSS THE EASTERN
CONUS BY LATE SATURDAY. THE GFS CONTINUES TO BE JUST A LITTLE DEEPER
WITH THE TROUGH AND TAPS INTO A LITTLE GULF MOISTURE FOR A QUICK
SHOT OF LIGHT PRECIP SUNDAY. TEMPS WOULD LIKELY BE WARM ENOUGH
FOR JUST RAIN, IF ANYTHING DEVELOPS OUTSIDE THE MOUNTAINS. BUT
A WINTRY MIX MAY BE POSSIBLE IN THE HIGH TERRAIN. THE ECMWF AND
CANADIAN ARE STILL DRY, AS IS THE MAJORITY OF THE GEFS AND GEPS
ENSEMBLES. SO WILL CONTINUE TO GO WITH THE NBM'S DRY FCST FOR
SUNDAY. DRY WX CONTINUES ACROSS THE AREA EARLY NEXT WEEK, WITH
TEMPS WARMING TO A FEW DEG ABOVE NORMAL.
AVIATION /18Z TUESDAY THROUGH SUNDAY/
AT KCLT AND ELSEWHERE: STILL HIGH CONFIDENCE FOR VFR THRU TONIGHT
AT THE TAF TERMINALS. BANDS OF CIRRUS WILL BE SEEN THIS AFTERNOON
AND EVENING, WITH CIRRUS CIGS FORMING BY MIDNIGHT OR SO AND THEN
JOINED BY ALTO DECKS CLOSER TO DAYBREAK. LOW PRESSURE MOVING NEAR
THE GULF COAST, COUPLED WITH SHORTWAVE COMING IN FROM THE WEST,
WILL RESULT IN RAPID EXPANSION OF PRECIP OVER THE AREA AROUND
15-17Z WED WHICH IS LIKELY TO CONTINUE THRU WED AFTERNOON. WINTRY
PRECIP IS LIKELY OVER MUCH OF THE REGION BUT WITH ONLY LIGHT TO
MODERATE ACCUMULATION; IFR VSBY IS LIKELY WITH ANY SNOW AND CIGS
WILL EVENTUALLY FALL TO IFR BY AFTERNOON WED. CONFIDENCE STILL
HIGH FOR A VIRTUALLY ALL SNOW EVENT FOR KAVL AND KHKY, AND ALMOST
ALL RAIN AT KAND. KCLT/KGSP/KGMU ARE MOST LIKELY TO EXPERIENCE A
WINTRY MIX. KCLT IS LIKELY TO SEE SOME SLEET MIX IN, PARTICULARLY
IN THE AFTERNOON, AND IF TEMPERATURES TREND BELOW FREEZING AS SOME
GUIDANCE SUGGESTS MAY HAPPEN, FZRA AND LIGHT ICE ACCRETION WOULD
LIKELY RESULT FOR A TIME. HANDLING THE P-TYPE TRANSITIONS AND ONSET
OF IFR IN PROB30 FOR NOW. AT KGSP/KGMU SNOW LOOKS MOST LIKELY BUT
WITH A POTENTIAL CHANGE TO RAIN; MORE SEVERE RESTRICTIONS ARE NOT
EXPECTED UNTIL AFTER 18Z AT THOSE SITES. WINDS WILL BE FAIRLY VRB
IN THE FIRST COUPLE HOURS OF THE PERIOD, BUT SE TO S WINDS WILL
PREVAIL THRU THIS EVENING. NE WINDS PREVAIL OVERNIGHT AND WED AT
ALL SITES EXCEPT KAVL, WHERE CONFIDENCE IS RELATIVELY LOW DUE TO
DIFFERING MODEL DEPICTIONS OF COLD-AIR DAMMING, BUT SE LOOKS MORE
LIKELY TO PREVAIL.
OUTLOOK: MOST ACCUMULATING PRECIP WILL END BY 00Z THU. SMALL
CHANCE OF -SHSN WED NIGHT ACROSS THE REGION, AND THU MORNING AT
KHKY/KCLT. WET SURFACES MAY FREEZE AS TEMPERATURES FALL BELOW
FREEZING WED NIGHT AND DEICING COULD BE NECESSARY THU MORNING. DRY
HIGH PRESSURE RETURNS LATE THURSDAY AND LINGERS INTO THE WEEKEND.
GSP WATCHES/WARNINGS/ADVISORIES
GA...WINTER WEATHER ADVISORY FROM 6 AM WEDNESDAY TO NOON EST
THURSDAY FOR GAZ010.
NC...WINTER WEATHER ADVISORY FROM 6 AM WEDNESDAY TO NOON EST
THURSDAY FOR NCZ033-035>037-048>053-056>059-062>065-
068>072-082-501>510.
SC...NONE.
SYNOPSIS...ARK
NEAR TERM...RWH/WIMBERLEY
SHORT TERM...ARK
LONG TERM...ARK
AVIATION...WIMBERLEY
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