810
FXUS62 KGSP 041528
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1128 AM EDT SUN MAY 4 2025
SYNOPSIS
QUIETER WEATHER IS EXPECTED TODAY THROUGH TUESDAY WITH NEAR
NORMAL TEMPERATURES. CLOUDS DIMINISH BY THIS AFTERNOON ALTHOUGH
A FEW SHOWERS MAY DEVELOP OVER THE MOUNTAINS. ANOTHER UNSETTLED
PATTERN LIKELY DEVELOPS WEDNESDAY WITH FREQUENT CHANCES FOR RAIN
THEN THROUGH FRIDAY.
NEAR TERM /THROUGH TONIGHT/
AS OF 1113 AM EDT SUNDAY: SHAPING UP TO BE A LOVELY AFTERNOON ACROSS
THE FCST AREA, WITH A COLD FRONT EXITING OUR EASTERN ZONES AND A
MORE TEMPERATE AND DRIER AIR MASS MOVING IN. SOME MORE CONGESTED
CLOUDS ARE NOTED ACROSS THE MTNS AND A FEW SHOWERS ARE MOVING
NORTHEAST UP THE GREAT VALLEY OF TN, DEVELOPING IN THE COLDER AIR
ALOFT COURTESY OF THE MID/UPPER LOW OVER THE CUMBERLAND PLATEAU
REGION. NO MAJOR CHANGES FOR THE AFTERNOON, BUT MINOR CHANGES TO
MTN PRECIP PROBS AND DEWPT/TEMP TRENDS BECAUSE OF FROPA.
OTHERWISE...SOME OF THE CAMS DEPICT SOME SPARSE RIDGETOP CONVECTION
DEVELOPING IN RESPONSE TO THE COLDER AIR ALOFT. A WEAK UPPER JETLET
WILL TRANSLATE ACROSS THE NC MOUNTAINS, HOWEVER, AND ITS POSITION
MAY SOMEWHAT IMPEDE INITIALIZATION...SO EXPECT ANY AFTERNOON
CONVECTION IN THE MOUNTAINS TO BE WIDELY SCATTERED AT BEST, WITH
LITTLE TO NO SEVERE THREAT. OTHERWISE, HIGH TEMPS WILL CLIMB INTO
THE LOW 70S, AND MOSTLY CLEAR SKIES WILL PERSIST INTO SUNDAY NIGHT.
SHORT TERM /MONDAY THROUGH TUESDAY/
AS OF 245 AM SUNDAY, KEY MESSAGES:
1. LITTLE TO NO CHANGE IN EXPECTATIONS FOR MON-TUE COMPARED TO
PREVIOUS COUPLE OF FCST CYCLES.
2. SCATTERED DIURNALLY DRIVEN SHOWERS REMAIN POSSIBLE NEAR THE
TN BORDER ON MONDAY. CHANCE OF PRECIPITATION TUESDAY TOO LOW TO
MENTION EVEN OVER THE MOUNTAINS.
3. TEMPS A FEW DEGREES BELOW NORMAL MONDAY, AND AROUND OR SLIGHTLY
ABOVE NORMAL TUESDAY.
CLOSED UPPER LOW WILL REMAIN CENTERED OVER THE MID TO LOWER OH
VALLEY MONDAY BUT BEGIN TO ROTATE TOWARD THE NE, BEGINNING TO MERGE
WITH SYNOPTIC TROUGH OVER CANADA BY WED MORNING. PROXIMITY TO THE
UPPER LOW WILL MAINTAIN RELATIVELY COOL MIDLEVELS AND PERMIT SMALL
DIURNAL INSTABILITY TO DEVELOP OVER THE MOUNTAINS, RESULTING IN
CHANCE POPS NEAR THE TN BORDER AT PEAK HEATING AND A SLIGHT-CHANCE
MENTION OF THUNDER. BY TUESDAY, THE MOUNTAINS AND CWA AT LARGE
SHOULD BE UNDER SUBSIDENT WEAK HIGH PRESSURE ON THE UPSTREAM
SIDE OF THE LOW, AND CONVECTION MOST LIKELY WILL BE CAPPED OFF BY
AN INVERSION, SO POPS REMAIN TOO LOW TO MENTION IN THE OFFICIAL
FCST. TEMPS WILL BE A FEW DEGREES BELOW NORMAL MONDAY AND MONDAY
NIGHT. UNDER MOSTLY CLEAR SKIES TEMPS TUE MORNING LOOK TO BE THE
COLDEST OF THE WEEK. A MODERATING AIRMASS WILL ALLOW HIGHS TO TREND
SLIGHTLY ABOVE NORMAL AGAIN ACROSS PARTS OF THE PIEDMONT TUESDAY.
LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/
AS OF 315 AM SUNDAY, KEY MESSAGES:
1. WIDESPREAD PRECIP CHANCES RETURN WEDNESDAY AS A WARM FRONT
ADVECTS OVER THE CWA, AND SOME CHANCE OF PRECIPITATION IS FORECAST
EACH DAY AND NIGHT THROUGH SATURDAY.
2. CONFIDENCE REMAINS LOW IN THE FORECAST IN THE MEDIUM RANGE
PERIOD, DUE TO UNCERTAINTY IN THE POSITION OF THE FRONT.
A WARM FRONT (BAROCLINIC ZONE) WILL SHIFT ACROSS THE SOUTHEAST
STATES TUESDAY NIGHT AND WEDNESDAY, ULTIMATELY EXTENDING FROM THE
SFC/UPPER LOW OVER THE HIGH PLAINS. MODELS DEPICT MOISTENING FROM
THE TOP DOWN OVER OUR CWA TUESDAY NIGHT IN ADVANCE OF THE FRONT
AND POPS CREEP BACK IN FROM SW TO NE BEGINNING EARLY WEDNESDAY
MORNING. CONFLUENT UPPER FLOW WITHIN THE DECAYING OMEGA BLOCK
WILL RETAIN WEAK SFC HIGH PRESSURE AND SOME DEGREE OF CAA OVER
THE SOUTHERN APPALACHIANS AND CAROLINAS. THE GLOBAL MODELS SUGGEST
DIABATIC COOLING WILL OCCUR WHERE PRECIP DEVELOPS, ALTHOUGH TRUE
CAD APPEARS UNLIKELY. WEDNESDAY'S TEMPS LOOK TO BE KEPT NEAR
70 WHERE RAIN BEGINS EARLY IN THE DAY. MODELS GENERALLY FEATURE
A QPF GRADIENT ACROSS THE CWA SEEMINGLY AS THE DRY SFC HIGH IS
INSUFFICIENT FOR THE WARM FRONT TO MODIFY.
AS THE EASTERN UPPER LOW MERGES WITH THE CANADIAN TROUGH,
HEIGHTS FALL OVER THE EASTERN SEABOARD AND A STRONGER COLD
FRONT DIVES SOUTHWARD TOWARD OUR AREA THURSDAY, POSSIBLY IN
BACKDOOR FASHION. THIS ADVANCING FRONT MAY DRIVE THE BAROCLINIC
ZONE SOUTHWARD, LEADING TO A DRYING TREND THU-FRI (AS DEPICTED
E.G. ON THE GFS), BUT COULD ALSO PROVIDE FORCING AND GENERATE
PRECIP FROM LINGERING MOISTURE (MORE LIKE THE ECMWF AND GDPS). THE
MODEL DIFFERENCES PARTLY RESULT FROM DIFFERING PLACEMENT OF THE
CENTRAL CONUS LOW AND POSSIBLY THE TIMING OF THE HEIGHT FALLS NEAR
THE EAST COAST. WITH POOR RUN-TO-RUN CONSISTENCY SO FAR AND WITH
SMALL ERRORS POSSIBLY RESULTING IN LARGE SENSIBLE WX DIFFERENCES,
WE RETAIN A RELATIVELY LONG DURATION POP LASTING INTO SATURDAY,
WITH LIKELY VALUES RETAINED DIURNALLY THU AND FRI. A REX BLOCK DOES
LOOK LIKELY TO TAKE SHAPE CIRCA THURSDAY IN THE UPPER MS VALLEY AND
CENTRAL PLAINS, AND THE DRY SFC HIGH FORCED SOUTHWARD THRU THE OH
VALLEY MAY PUSH IN AND DRY US OUT SATURDAY; WITH A SEEMINGLY GROWING
CONSENSUS FOR THAT, POPS ARE KEPT NO BETTER THAN CHANCE RANGE ON
SATURDAY FOR NOW, AND SHOULD TREND LOWER IF THE CONSENSUS HOLDS.
LOCALLY HEAVY RAINFALL IS CURRENTLY THE MAIN IMPACT WEATHER FOR
THE PERIOD. TEMPS WILL TREND UPWARD THURSDAY BUT PROBABLY WILL FALL
BELOW NORMAL AGAIN FRIDAY AND/OR SATURDAY BEHIND THE BACKDOOR FRONT.
AVIATION /16Z SUNDAY THROUGH THURSDAY/
AT KCLT AND ELSEWHERE: MVFR TO IFR CEILINGS WILL LINGER FOR A BIT
LONGER, BUT SHOULD SCATTER OUT QUICKLY NOW THAT THE SUN IS RISING.
ALTHOUGH SOME RIDGETOP SHOWERS CAN BE EXPECTED IN THE MOUNTAINS
THIS AFTERNOON, COVERAGE APPEARS TOO LOW FOR A MENTION AT KAVL,
SO ONLY SCATTERED CU COVERAGE IS MENTIONED THERE. OTHER SITES GO
FEW/SKC THROUGH THE DAY AND INTO THE END OF THE PERIOD SUNDAY NIGHT.
GENERALLY EXPECT 5-10KT SW WINDS BECOMING W TOWARD THE END OF
THE PERIOD.
OUTLOOK: DRIER WEATHER CONTINUES SUNDAY NIGHT INTO MONDAY.
VFR EXPECTED THROUGH THE FIRST PART OF THE WEEK.
GSP WATCHES/WARNINGS/ADVISORIES
GA...NONE.
NC...NONE.
SC...NONE.
SYNOPSIS...WIMBERLEY
NEAR TERM...MPR/PM
SHORT TERM...WIMBERLEY
LONG TERM...WIMBERLEY
AVIATION...MPR
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