264
FXUS62 KGSP 180529
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1229 AM EST TUE FEB 18 2025
SYNOPSIS
DRY HIGH PRESSURE LINGERS THROUGH TUESDAY. 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 TODAY/
AS OF 125 AM EST TUESDAY: CIRRUS WILL SPREAD ACROSS THE AREA EARLY
THIS MORNING WITH SOME ALTOCU OR STRATOCU FOR THE NORTHERN MOUNTAINS
OR I-40 CORRIDOR. WINDS WILL BE LIGHT. THE CLOUDS MAY SLOW COOLING,
BUT GIVEN THE COLD START, EXPECT LOWS 5 TO 10 DEGREES BELOW NORMAL.
OTHERWISE, VERY BROAD/FLAT UPPER TROFING WILL REMAIN WELL TO OUR
NORTH THRU THE PERIOD. THIS WILL KEEP ZONAL, WLY UPPER FLOW OVER THE
SOUTHEAST. AT THE SFC, ELONGATED CANADIAN HIGH PRESSURE WILL REMAIN
OVER OUR AREA TONIGHT AND TOMORROW. THE HIGH DOES SHIFT EAST ON
TUESDAY ALLOWING SFC WINDS TO TOGGLE AROUND TO E/SE DURING THE AFTN,
ALTHOUGH THEY SHOULD REMAIN LIGHT (IE, NO MORE THAN 5 KTS). BROAD
AREAS OF MORE MOIST AIR WILL GRADUALLY ENCROACH UPON OUR AREA BY THE
END OF THE PERIOD LATE TUESDAY, BUT ANY PRECIPITATION APPEARS
UNLIKELY AS PROFILES DON'T APPEAR TO MOISTEN UP SUBSTANTIALLY UNTIL
JUST BEYOND THE PERIOD EARLY WEDNESDAY. IN ADDITION, SCT TO BKN HIGH
CLOUDS WILL PERSIST OVER OUR AREA FOR MOST OF TOMORROW AND SHOULD
HELP KEEP HIGH TEMPERATURES ABOUT A CATEGORY BELOW CLIMATOLOGY FOR
MOST LOCATIONS.
SHORT TERM /TONIGHT THROUGH THURSDAY/
AS OF 130 PM MON: CONFIDENCE HIGH ON DEVELOPMENT OF A MILLER A-TYPE
LOW DEVELOPING ALONG THE GULF COAST TUESDAY NIGHT, AND MODELS HAVE
TRENDED NO FURTHER NORTH WITH THE LOW TRACK. AT THIS POINT, THE
GREATEST CONTRIBUTOR TO UNCERTAINTY IS ARGUABLY TEMPERATURE TRENDS
THRU THE EVENT. MODELS SEEM TO BE STRUGGLING WITH HOW THEY CHANGE AS
PRECIP FALLS, GIVEN THE VERY COLD AND DRY RIDGE TO OUR NORTH
RESULTING IN LARGE DEWPOINT DEPRESSIONS EARLY IN THE EVENT, BUT ALSO
GENERALLY ONSHORE LOW-LEVEL FLOW, AND STRONG FRONTOGENETIC/UPGLIDE
RESPONSE WHICH DEVELOPS AS THE LOW REACHES THE ATLANTIC WEDNESDAY
AFTERNOON. THERE IS STILL LIKELY TO BE A TRANSITION ZONE, IN WHICH A
WARM NOSE WILL LEAD TO SLEET AND/OR FREEZING RAIN. THIS ZONE HAS
TRENDED NARROWER ON RECENT MODEL RUNS, WHICH IS MORE IN LINE WITH
MILLER-A CLIMATOLOGY. SURFACE TEMPS WILL BE ESSENTIAL IN DETERMINING
ANY SNOW OR ICE ACCUMULATIONS (PARTICULARLY THE FORMER). THE ECMWF,
WHICH ONCE HAD BEEN SUBSTANTIALLY COLDER AND WETTER/SNOWIER OWING TO
ITS MORE NORTHERLY LOW TRACK, NOW DEPICTS WARMING ABOVE FREEZING FOR
A PORTION OF THE DAY. THE OTHER MODELS HAVE TRENDED SLIGHTLY COLDER
FOR MOST OF THE EVENT, BUT MOSTLY DEPICT TEMPERATURES HOVERING JUST
ABOVE FREEZING IN OUR NORTH AND IN THE MID-30S SOUTH DURING THE MOST
LIKELY TIME OF PRECIP.
WITH MODELS HAVING COME MORE INTO CONSENSUS FOR A MORE SOUTHERLY LOW
TRACK, THAT IS LIKELY A BIG REASON WHY QPF HAS TRENDED DOWN OVER THE
PAST TWO OR THREE MODEL CYCLES. HOWEVER, SOME OF TODAY'S 12Z MODELS
SHOW A SLIGHT UPWARD TICK IN 6-HR AMOUNTS FOR WEDNESDAY MORNING, AND
THERE IS STILL TIME FOR A CHANGE EITHER WAY. MORE MEMBERS ARE
TRENDING LOW ENOUGH WITH QPF, AND/OR NOT DEPICTING PRECIP AT ALL,
WHICH IS REFLECTED IN LOWER POPS, NOW IN HIGH-LIKELY RANGE AS OPPOSED
TO THE CATEGORICAL NUMBERS PREVIOUSLY ADVERTISED. MORE SLEET IS BEING
INCLUDED WEDNESDAY AFTERNOON IN THE US 74 AND I-85 CORRIDORS, MORE OR
LESS EAST OF I-26, WHICH BRINGS SNOW TOTALS DOWN (SLEET COUNTS AS
SNOW FOR ACCUMULATION PURPOSES, BUT HAS A LOWER ICE-LIQUID RATIO).
IT IS STILL LIKELY TO BE AN ALL-SNOW EVENT IN OUR MOUNTAINS AND NORTH
OF I-40 IN THE PIEDMONT, BUT WITH LOWER QPF AMOUNTS ARE NOW 1-2 FOR
LOWER ELEVATIONS AND 2-4 IN HIGH ELEVATIONS. WE MAY BE ABLE TO HANDLE
THIS WITH A WINTER WX ADVISORY, A DECISION WHICH COULD BE MADE
TONIGHT BUT MORE LIKELY TOMORROW, PARTICULARLY AS THE EXTENT OF
ACCUMS ELSEWHERE IS MORE UNCERTAIN. A SMALL AREA OF FREEZING RAIN
STILL IS EXPECTED TO DEVELOP BY EARLY WED EVENING AROUND CHARLOTTE
AND POINTS SOUTH, WHICH RESULTS IN SMALL ICE ACCUMS OF A COUPLE
HUNDREDTHS IN THOSE AREAS; STILL THINK PRECIP COULD END BEFORE THE
WARM NOSE BECOMES STRONG ENOUGH TO RESULT IN DEVELOPMENT OF FZRA.
LOSS OF ICE NUCLEI COULD ALSO BE A FACTOR IN SUCH A TRANSITION. THERE
HAS BEEN A TREND TOWARD LIGHT PRECIP DEVELOPING OVERNIGHT WED NIGHT
WITH WRAPAROUND MOISTURE AHEAD OF THE CLOSED LOW PASSING TO OUR
NORTH. POPS ARE SLOWER TO DECLINE IN THAT PERIOD PARTICULARLY IN
WESTERN NC; SAID WRAPAROUND MOISTURE REPLENISHES THE ICE NUCLEI AND
CAA WILL BE ONGOING IN LOW LEVELS SO REMAINING CHANCES ARE PRETTY
MUCH ALL SNOW FROM MIDNIGHT ONWARD. NORTHWEST FLOW SNOWFALL STILL
LOOKS TO CONTINUE THURSDAY MORNING ALONG THE TN BORDER BUT PROBABLY
WILL END BY NOON.
LOWS WED NIGHT WILL BE IN THE TEENS IN THE MOUNTAINS AND 20S
ELSEWHERE. HIGHS THU WILL BE 15-20 BELOW NORMAL. DRY WX AND MOSTLY
CLEAR SKIES THU NIGHT STILL LOOK TO MAKE THAT THE COLDEST NIGHT OF
THE 7-DAY PERIOD, WITH SINGLE DIGITS IN HIGH ELEVATIONS, LOWER TEENS
FOR THE MOUNTAINS AND NORTHERN FOOTHILLS, AND UPPER TEENS TO NEAR 20
ELSEWHERE.
LONG TERM /THURSDAY NIGHT THROUGH MONDAY/
AS OF 230 PM MON: ARCTIC ANTICYCLONE WILL MOVE ACROSS THE MIDDLE
MISSISSIPPI VALLEY FRIDAY, SUBSEQUENTLY MIGRATING ACROSS THE
SOUTHEAST STATES AND CENTERING OFF THE NC COAST BY SATURDAY NIGHT.
THE NEXT FEATURE OF INTEREST IS A WELL DEFINED SHORTWAVE WHICH WILL
MOVE OUT OF THE DESERT SOUTHWEST EARLY IN THE WEEKEND. THE 17/12Z GFS
IS DEEPER THAN THE OTHER DETERMINISTIC MODELS WITH THE WAVE AND
INITIATES ANOTHER MILLER-A OR SIMILAR COASTAL LOW, AND BRINGS
WIDESPREAD PRECIP TO THE AREA SUNDAY. THIS IS DEPICTED ON A FEW GEFS
AND GEPS MEMBERS, BUT GIVEN THE RANGE AND RELATIVELY NEW APPEARANCE
OF THIS IN GUIDANCE OUTPUT, NO MENTIONABLE POP IS YET BEING INCLUDED.
THE PERIOD IS THUS DRY. TEMPERATURES WILL MODERATE A FEW DEGREES EACH
DAY, RISING ALMOST BACK TO NORMAL FOR SUNDAY.
AVIATION /06Z TUESDAY THROUGH SATURDAY/
AT KCLT AND ELSEWHERE: VFR CONDITIONS EXPECTED THROUGH THE PERIOD.
HIGH PRESSURE SLOWLY BUILDS INTO THE AREA THROUGH THE PERIOD.
PERIODS OF MAINLY CIRRUS MOVE ACROSS THE AREA BUT SOME LOW ALTOCU OR
HIGH STRATOCU MAY MOVE ACROSS THE MOUNTAINS OR KHKY. LIGHT AND
VARIABLE OR LIGHT N WIND BECOMES LIGHT S FOR THE AFTERNOON THEN BACK
TO LIGHT NE OR LIGHT AND VARIABLE THIS EVENING. KAVL WILL SEE LIGHT
N WIND THROUGHOUT, BUT CAN'T RULE OUT SOME LIGHT SSE DURING THE
AFTERNOON.
OUTLOOK: RESTRICTIONS WILL LIKELY RETURN TO THE AREA ON WEDNESDAY
WITH A MIX OF WINTRY WEATHER. DRY HIGH PRESSURE RETURNS THURSDAY
AND LINGERS INTO THE WEEKEND.
GSP WATCHES/WARNINGS/ADVISORIES
GA...NONE.
NC...NONE.
SC...NONE.
SYNOPSIS...WIMBERLEY
NEAR TERM...CP/JPT/RWH
SHORT TERM...WIMBERLEY
LONG TERM...WIMBERLEY
AVIATION...RWH
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