033
FXUS62 KGSP 181949
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
249 PM EST TUE FEB 18 2025
SYNOPSIS
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. A DRY PATTERN WITH A WARMING TREND IS EXPECTED TO BEGIN OVER
THE WEEKEND, WITH ABOVE-NORMAL TEMPERATURES EXPECTED TO RETURN EARLY
NEXT WEEK.
NEAR TERM /THROUGH WEDNESDAY/
AS OF 210 PM: ARCTIC AIRMASS EXTENDS FROM THE NORTHERN PLAINS ACROSS
THE OHIO VALLEY TO THE CHESAPEAKE BAY REGION, EVIDENCED BY DEWPOINTS
AT OR BELOW ZERO ACROSS THE LATTER AREA. WE'VE MIXED DOWN SOME OF
THAT DRY AIR, RESULTING IN DEWPOINTS HAVING FALLEN INTO THE UPPER
TEENS IN PORTIONS OF OUR CWA. THEY WILL REBOUND A BIT WITH THE LOSS
OF DIURNAL MIXING, BUT WILL REMAIN LOW TONIGHT. CIRRUS/ALTOSTRATUS
CLOUD COVER WILL FILL IN ACROSS THE AREA OVERNIGHT WHICH WILL LIMIT
RADIATIONAL COOLING. MEANWHILE, AS UPPER TROUGH SWINGS ACROSS THE
SOUTHERN PLAINS AND MS VALLEY, MILLER-A SFC CYCLONE WILL DEVELOP
AND TRACK SOUTH OF THE CWA OVER THE COURSE OF WEDNESDAY. NO
GENERAL CHANGE IN THIS THINKING. WARM UPGLIDE OVER THE DRY HIGH,
COUPLED WITH DIVERGENCE IN RR QUAD OF AMPLIFYING 250MB JET, WILL
LEAD TO THE DEVELOPMENT OF LIGHT PRECIP ACROSS THE AREA DURING THE
MORNING. SOME FLAVOR OF DIABATICALLY ENHANCED CAD MAY TECHNICALLY
DEVELOP, ALTHOUGH THE CLOSED UPPER LOW APPROACHING THE AREA BY THE
END OF THE PERIOD (00Z THU) SUGGESTS IT WILL ERODE FAIRLY QUICKLY.
12Z GUIDANCE GENERALLY AGREED PRETTY WELL WITH THE PREVIOUS FORECAST
IN TERMS OF TIMING; QPF WENT A LITTLE UPWARD ON SOME GUIDANCE AND
DOWN ON OTHERS. CAMS SUGGEST THE VERY DRY AIRMASS/WEDGE WILL BE
A BIGGER FACTOR IN LIMITING PRECIP AMOUNTS IN OUR EAST THAN SOME
MODELS HAD PREVIOUSLY SUGGESTED; A "HOLE" CAN BE SEEN IN MODELED
REFLECTIVITY PROGS. THROUGH THE PASSAGE OF THE CYCLONE, MANY AREAS
IN OUR EAST ARE NOT EXPECTED EVEN TO SEE 0.10" LIQUID QPF. WITH
MORE MODELS DEPICTING MINIMAL QPF, POPS HAVE FALLEN A BIT FURTHER
IN MANY AREAS, BUT LIKELY RANGE VALUES ARE STILL FORECAST IN ALL
ZONES AT SOME POINT DURING THE DAY.
ALTHOUGH MOST GUIDANCE HAS ALSO TRENDED SLIGHTLY WARMER, EVAPORATIVE
COOLING STILL COULD BE A BIG FACTOR IN PRECIP TYPE ESPECIALLY
AT ONSET. OVERNIGHT TEMPS LOOK TO REMAIN ABOVE FREEZING IN MOST
OF OUR SC/GA ZONES EXCEPT FOR THE HIGHER ELEVATION AREAS. IT
IS POSSIBLE SOME AREAS MAY SEE TEMPS DIP SLIGHTLY COLDER IN
LATE MORNING AFTER THE PERIOD THAT REPRESENTS OUR FORECAST "LOW
TEMP." WHERE WET-BULBS ARE NEAR OR BELOW FREEZING, PRECIP LIKELY
WILL BEGIN AS SNOW. A TRANSITION ZONE STILL IS LIKELY TO DEVELOP
AS A WEAK WARM NOSE DEVELOPS VIA THE UPGLIDE, LATE MORNING TO
MID-AFTERNOON. SLEET WOULD BE LIKELY TO MIX IN WHERE THAT DEVELOPS,
BUT FREEZING RAIN COULD ALSO RESULT WHERE SFC TEMPS ARE BELOW
FREEZING. THE 12KM NAM TOOK A SHARP TURN COLDER AFTER THE ONSET
OF PRECIP, WHICH COMBINED WITH ITS SOMEWHAT STRONGER WARM NOSE
LEADS IT TO GENERATE APPRECIABLY MORE FZRA THAN OTHER GUIDANCE,
EVEN THE 3KM NAM. A SLEET MENTION WAS RETAINED IN OUR SOUTHEAST
CORNER (NEAR CLT) BUT WITH TEMPS HOVERING JUST ABOVE FREEZING IN
THAT AREA THROUGH THE BULK OF PRECIP NO FZRA IS MENTIONED. PRECIP
WILL BECOME LESS LIKELY BY AFTERNOON OVER THE MOUNTAINS (EXCEPT
NEAR THE TN BORDER). ICE NUCLEI MAY BE LESS AVAILABLE AS DRYING
OCCURS FROM THE TOP DOWN, FROM WEST TO EAST IN THE AFTERNOON. AREAS
THAT ARE BELOW FREEZING COULD SEE SOME FREEZING DRIZZLE DEVELOP,
BUT CONFIDENCE IS LOW ON THAT OCCURRENCE. SNOW AMOUNTS IN THE
NORTHERN PORTIONS OF THE NORTHERN TIER OF GA/SC ZONES ARE EXPECTED
TO BE LESS THAN A HALF INCH, AND THERE APPEARS NO NEED TO EXTEND
THE WINTER WX ADVISORY THERE. AMOUNTS OF SNOW/SLEET ARE SLIGHTLY
MORE IN YORK/CHESTER COUNTIES, BUT THE EXPECTATION OF TEMPERATURES
REMAINING ABOVE FREEZING SUGGESTS MINIMAL TRAVEL IMPACTS THRU 00Z
THU, SO THEY TOO ARE BEING OMITTED. A CHANGE TO FZRA IS POSSIBLE
IN THOSE COUNTIES WED NIGHT, BUT THAT CHANCE APPEARS TOO LOW FOR
AN ADVISORY ON ITS OWN.
SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/
AS OF 145 PM TUESDAY: CYCLONE WILL PULL AWAY FROM THE CAROLINA COAST
BY THURSDAY MORNING, WITH CENTER OF AN UPPER LOW FORECAST TO BARREL
ACROSS THE OHIO VALLEY AND MID-ATLANTIC WED NIGHT/THU. LOW LEVEL
FLOW WILL BRIEFLY BACK ACROSS OUR AREA IN RESPONSE TO THIS LATTER
FEATURE...MAINTAINING WEAK LOW-LEVEL LIFT AND AMPLE MOISTURE WED
NIGHT. THIS COULD RESULT IN SOME LIGHT SNOW SHOWERS/FLURRIES ALONG
WITH POCKETS OF DRIZZLE OR FREEZING DRIZZLE DURING THE EVENING, AS
TEMPS DIP INTO THE 20S ACROSS MUCH OF THE AREA BY THU MORNING.
FORCING WILL DEEPEN AFTER MIDNIGHT, AS THE UPPER LOW BEGINS TO PASS
NORTH OF THE AREA...WITH THE EXIT REGION OF ASSOCIATED STRONG UPPER
JET MAX EXPECTED TO MOVE OVER THE AREA BETWEEN 06-12Z THU. THIS IS
FORECAST TO ENHANCE THE POTENTIAL FOR ACCUMULATING NORTHWEST FLOW
SNOW SHOWERS ACROSS THE MOUNTAINS...WHILE PERHAPS SUPPORTING A
QUICK-MOVING BATCH OF SNOW SHOWERS (20-30 POPS) DEVELOPING OVER
PORTIONS OF THE PIEDMONT BETWEEN DAYBREAK AND LATE MORNING. THIS
LATTER AREA COULD BRING ADDITIONAL SNOWFALL OF UP TO AN INCH TO
PORTIONS OF THE PIEDMONT. HOWEVER, CONFIDENCE IN THIS SCENARIO IS
LOW AT THIS POINT. OTHERWISE, THE MAIN IMPACT IS EXPECTED TO BE
ADDITIONAL ACCUMULATIONS OF 1-3 INCHES ACROSS PORTIONS OF THE
COUNTIES BORDERING TN/NC DURING THE FIRST HALF OF THE SHORT TERM.
NORTHWEST FLOW SNOW SHOWERS WILL TAPER OFF TO FLURRIES BY THU
EVENING, WITH DRY CONDITIONS EXPECTED THROUGH THE REMAINDER OF THE
PERIOD. TEMPERATURES THU/THU NIGHT WILL BE QUITE COLD...AROUND 20
DEGREES BELOW NORMAL. GUSTY WINDS DEVELOPING IN THE COLD ADVECTION
FLOW...WITH GUSTS IN THE 30-40 MPH RANGE EXPECTED ACROSS MUCH OF THE
MOUNTAINS...WILL YIELD WIND CHILL VALUES IN THE SINGLE DIGITS OR
LOWER ACROSS MUCH OF THE MOUNTAINS. HOWEVER, IT APPEARS FOR NOW THAT
VALUES REACHING COLD WX ADVISORY CRITERIA WILL PRIMARILY BE CONFINED
TO ELEVATIONS ABOVE ~4000 FEET. LOW WIND CHILL VALUES WILL CONTINUE
INTO FRI MORNING, BUT A DECENT WARM-UP IS ANTICIPATED (MAXES 10-12
DEGREES BELOW NORMAL) DURING THE AFTERNOON, AS HEIGHTS RISE WITH
UPPER TROUGH PULLING AWAY FROM THE EAST COAST.
LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/
AS OF 200 PM TUESDAY: A DRY PATTERN WILL BE ESTABLISHED ACROSS THE
REGION DURING THE EXTENDED...WITH A FAST W/NW FLOW ALOFT EXPECTED TO
ENCOMPASS MUCH OF THE COUNTRY. MULTIPLE DAMPENING SHORT WAVE TROUGHS
ARE EXPECTED TO SWEEP ACROSS THE REGION AT VARIOUS TIMES THROUGHOUT
THE PERIOD. THESE COULD BRING VERY BRIEF PERIODS OF NORTHWEST FLOW
LIGHT SNOW OR RAIN SHOWERS TO THE MOUNTAINS...ESPECIALLY LATER IN
THE PERIOD, BUT ANY IMPACTS SHOULD BE MINIMAL. OTHERWISE, THE
AIRMASS IS EXPECTED TO REMAIN TOO DRY TO SUPPORT PRECIP DEVELOPMENT.
A WARMING TREND THAT WILL BEGIN FRIDAY IS EXPECTED TO CONTINUE
THROUGH MUCH OF THE PERIOD, WITH TEMPERATURES FORECAST TO WARM TO
NEAR-NORMAL LEVELS BY SUNDAY...AND PERHAPS TO AS MUCH AS 10 DEGREES
ABOVE CLIMO BY THE END OF THE PERIOD.
AVIATION /20Z 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...JDL
NEAR TERM...WIMBERLEY
SHORT TERM...JDL
LONG TERM...JDL
AVIATION...WIMBERLEY
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