698
FXUS62 KGSP 011045
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
645 AM EDT FRI AUG 1 2025
SYNOPSIS
ONE LAST HOT AND HUMID DAY ON TAP WITH WIDESPREAD SHOWERS AND
THUNDERSTORMS DEVELOPING THIS AFTERNOON AND EVENING. A FEW STRONG TO
SEVERE STORMS, AS WELL AS ISOLATED FLASH FLOODING, WILL BE POSSIBLE
WITH TODAY'S DIURNAL ACTIVITY. COLD AIR DAMMING DEVELOPS THIS
WEEKEND AND LINGERS INTO THE NEW WORKWEEK BRINGING MUCH NEEDED
RELIEF FROM THE HEAT AND HUMIDITY IN THE FORM OF COOLER AND BELOW
NORMAL HIGH TEMPERATURES. SHOWER AND THUNDERSTORM CHANCES STICK
AROUND THROUGH NEXT WEEK BUT A LULL MAY DEVELOP SUNDAY INTO MONDAY.
NEAR TERM /THROUGH TONIGHT/
AS OF 150 AM FRIDAY: FRONTAL BOUNDARY DRAPED FROM THE MID-
MISSISSIPPI VALLEY THROUGH THE NORTHERN MID-ATLANTIC EARLY THIS
MORNING IS FORECAST TO REMAIN NORTH OF OUR FORECAST AREA THROUGH
TODAY...BEFORE NUDGING S/SW THROUGH THE CWA TONIGHT AS ANOTHER ROUND
OF HEIGHT FALLS OVERSPREADS THE NORTHEAST QUADRANT OF THE COUNTRY
LATE TODAY/TONIGHT. MORNING FOG/LOW STRATUS...MAINLY OVER THE
MOUNTAIN VALLEYS, BUT ALSO IN PATCHY AREAS EAST OF THE MOUNTAINS
SHOULD GIVE WAY TO NO WORSE THAN PARTLY CLOUDY SKIES BY LATE
MORNING, ALLOWING FOR MODERATE/SEASONAL LEVELS OF DESTABILIZATION
THIS AFTERNOON. USUAL TERRAIN EFFECTS ALONG WITH PRE-FRONTAL/THERMAL
TROUGH WILL PROVIDE THE PRIMARY IMPETUS FOR CONVECTIVE INITIATION
THIS AFTERNOON, WITH SUBSEQUENT OUTFLOW BOUNDARIES INITIATING
ADDITIONAL CELLS. INCREASING MID/UPPER LEVEL FLOW WILL RESULT IN AN
INCREASE OF 0-3KM SHEAR TO 15-20 KTS THIS AFTERNOON, AND THIS WILL
BE SUFFICIENT TO PROMOTE POTENTIAL FOR CLUSTERING OF CELLS ALONG
OUTFLOWS...SUGGESTING NUMEROUS COVERAGE OF CONVECTION...60-70 POPS
ACROSS MOST OF THE CWA THIS AFTERNOON. THIS WILL ALSO RESULT IN AN
UPTICK IN THE POTENTIAL FOR ISOLATED SEVERE DOWNBURSTS...JUSTIFYING
A MARGINAL RISK OF SEVERE STORMS FROM SPC. ADDITIONALLY, THERE WILL
BE SOME POTENTIAL FOR LOCALLY HEAVY/POSSIBLY EXCESSIVE RAINFALL, AS
WARM CLOUD DEPTHS ARE EXPECTED TO BE WELL OVER 10KFT WITH PWATS OF
AROUND 2 INCHES. WHILE INDIVIDUAL CELL MOVEMENT IS EXPECTED TO BE IN
THE 10-15 KTS RANGE, THE POTENTIAL FOR TRAINING CELLS AND POSSIBLY
SLIGHT BACK-BUILDING WITHIN MULTICELL CLUSTERS COULD RESULT IN LOCAL
EXTREME RAINFALL RATES. FINALLY, ONE LAST DAY OF HOT CONDITIONS IS
EXPECTED BEFORE A SIGNIFICANT COOL DOWN, WITH ENOUGH INSOLATION/HEAT
AND HUMIDITY EXPECTED ACROSS THE LAKELANDS TO WARRANT A HEAT
ADVISORY FOR ELBERT, ABBEVILLE, AND GREENWOOD COUNTIES.
CONVECTION IS EXPECTED TO LINGER INTO AT LEAST THE EARLY PART OF
THE OVERNIGHT, WITH THE FRONT PROVIDING A CONTINUED SOURCE OF LIFT
DESPITE DIMINISHING INSTABILITY, WITH AT LEAST SLIGHT CHANCE POPS
WARRANTED ACROSS THE ENTIRE CWA THROUGH 12Z SATURDAY. CONVECTIVE
THREATS SHOULD WANE STEADILY THROUGH THE NIGHT, ALTHOUGH THE
POTENTIAL FOR LOCALLY HEAVY RAINFALL WILL PERSIST, ESPECIALLY
IF ANY CELLS ARE ABLE TO BECOME ANCHORED ALONG THE BOUNDARY IN
LIGHT OF STEERING FLOW DECREASING TO LESS THAN 5 KTS. MIN TEMPS
ARE FINALLY EXPECTED TO RETURN TO NORMAL IN THE LOWER THETA-E AIR
NORTH OF THE BOUNDARY.
SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/
AS OF 100 AM EDT FRIDAY...
KEY MESSAGES:
1) COLD AIR DAMMING BRINGS MUCH NEEDED RELIEF FROM THE HEAT AND
HUMIDITY THIS WEEKEND
2) WELL BELOW NORMAL HIGH TEMPERATURES EXPECTED
3) SHOWER AND THUNDERSTORM CHANCES CONTINUE BUT DRIER CONDITIONS MAY
DEVELOP ON SUNDAY
SFC HIGH PRESSURE STRETCHING FROM THE GREAT LAKES TO THE NORTHEAST
WILL NOSE DOWN THE APPALACHIANS THIS WEEKEND ALLOWING FOR AN
ABNORMALLY STRONG SUMMER COLD AIR DAMMING EVENT.
THE LATEST RUN OF THE NBM IS TRENDING COOLER REGARDING HIGHS THIS
WEEKEND. HIGH TEMPERATURES SATURDAY AFTERNOON EXPECTED TO BE ~12-18
DEGREES COOLER COMPARED TO THIS AFTERNOON. HIGHS EAST OF THE
MOUNTAINS WILL STRUGGLE TO CLIMB INTO THE MID 70S TO LOW 80S. HIGHS
ACROSS THE MOUNTAIN VALLEYS WILL RANGE FROM THE UPPER 60S TO UPPER
70S WITH ELEVATIONS ABOVE 3500 FT RANGING FROM THE MID 50S TO MID
60S. THIS SHOULD ALLOW HIGHS TO END UP ~8-12 DEGREES BELOW NORMAL
THROUGH THE WEEKEND. LOWS EACH NIGHT WILL RANGE FROM THE MID 50S TO
LOWER 60S ACROSS THE MOUNTAINS, WITH LOWS EAST OF THE MOUNTAINS
RANGING FROM THE LOWER TO UPPER 60S. I THINK MOST OF US WILL AGREE
THAT THIS WILL BE A WELL DESERVED BREAK FROM THE HEAT AND HUMIDITY!
SHOWER AND THUNDERSTORM CHANCES WILL LINGER THROUGH THE SHORT TERM,
ESPECIALLY ON SATURDAY, BUT DRIER CONDITIONS MAY DEVELOP FOR SOME
LOCATIONS ON SUNDAY. HOWEVER, CONFIDENCE IS LOW REGARDING THE DRYING
POTENTIAL ON SUNDAY AS GLOBAL MODEL GUIDANCE ARE NOT IN AGREEMENT.
THE LATEST GFS HAS DRY CONDITIONS GRADUALLY DEVELOPING SUNDAY,
LINGERING INTO SUNDAY NIGHT, AS IT DEPICTS THE SFC HIGH NUDGING
FARTHER SOUTH COMPARED TO THE REST OF THE GUIDANCE. THE LATEST
ECMWF, CANADIAN, AND NAM HAVE DRIER CONDITIONS DEVELOPING MAINLY
ACROSS WESTERN NC AS THE MODELS ALL DEPICT THE SFC HIGH REMAINING
FARTHER NORTH COMPARED TO THE GFS. THUS, CONFIDENCE ON SUNDAY'S POPS
IS LOW. WITH THE WEDGE IN PLACE, SFC INSTABILITY WILL BE VERY
LIMITED MAKING ANY SEVERE THREAT HARD TO COME BY. WITH PWATS
EXPECTED TO GRADUALLY DROP THROUGH THE WEEKEND, HYDRO CONCERNS WILL
GRADUALLY LOWER THROUGH THE WEEKEND AS RAINFALL RATES BECOME LESS
EFFICIENT, ESPECIALLY ON SUNDAY.
LONG TERM /MONDAY THROUGH THURSDAY/
AS OF 100 AM EDT FRIDAY...
KEY MESSAGES:
1) COLD AIR DAMMING LINGERS THROUGH MOST OF THE NEW WORKWEEK
2) HIGHS WILL GENERALLY BE ON A WARMING TREND BUT WILL REMAIN BELOW
NORMAL
3) DRIER CONDITIONS POSSIBLE AGAIN ON MONDAY BEFORE SHOWER AND
THUNDERSTORM CHANCES RAMP UP THE REST OF THE WORKWEEK
WITH NO REAL MECHANISM TO ERODE THE COLD AIR DAMMING WEDGE, IT LOOKS
TO REMAIN IN PLACE PER WINDS REMAINING STEADILY NE'LY EAST OF THE
MOUNTAINS THROUGH THE LONG TERM. THUS, MOTHER NATURE WILL CONTINUE
TO THROW US A BONE FOR EARLY AUGUST WITH BELOW NORMAL HIGHS STICKING
AROUND. HIGH TEMPERATURES EACH DAY SHOULD END UP A FEW TO SEVERAL
DEGREES BELOW NORMAL THROUGH MUCH OF THE NEW WORKWEEK DESPITE A
GENERAL WARMING TREND. PWATS WILL REMAIN LOW AGAIN ON MONDAY BEFORE
GRADUALLY INCREASING THE REST OF THE PERIOD AS A STALLED FRONTAL
BOUNDARY NUDGES NORTHWARD TOWARDS THE CAROLINA COAST. THUS, THE
BRIEF LULL IN CONVECTION MAY LINGER THROUGH MONDAY BUT CONFIDENCE IS
LOW DUE TO MODEL DISAGREEMENT. THE LATEST GFS SHOWS DRY CONDITIONS
OVER THE CWA ON MONDAY WITH THE SFC HIGH BUILDING FARTHER SOUTH.
MEANWHILE, THE LATEST ECMWF AND CANADIAN SHOW THE HIGH REMAINING
FARTHER NORTH WITH POPS GRADUALLY INCREASING THROUGHOUT MONDAY.
THUS, CONFIDENCE ON MONDAY'S POPS IS LOW. GLOBAL GUIDANCE DOES
GENERALLY AGREE THAT BETTER COVERAGE OF CONVECTION WILL INCREASE THE
REMAINDER OF THE WORKWEEK AS THAT STALLED BOUNDARY PROVIDES A BETTER
INFLUX OF MOISTURE. THIS MAY ALLOW THE HEAVY RAINFALL/FLOODING
THREAT TO RETURN, ESPECIALLY MID TO LATE WEEK. THE SEVERE WEATHER
POTENTIAL SHOULD REMAIN LOW THROUGH THE PERIOD WITH CAD LIMITING
DESTABILIZATION.
AVIATION /12Z FRIDAY THROUGH TUESDAY/
AT KCLT AND ELSEWHERE: AN AREA OF FOG/LOW STRATUS HAS DEVELOPED
ACROSS WESTERN PORTIONS OF UPSTATE SC THIS MORNING...MAINLY
IMPACTING KAND, ALTHOUGH FEW/SCT004 HAS RECENTLY MOVED INTO
KGMU. EASTWARD EXPANSION OF THE DECK HAS SLOWED, SO IT REMAINS
UNCERTAIN IF RESTRICTIONS WILL MAKE IT AS FAR AS KGSP. THEREFORE,
FIRST GUESS WITH THE 12Z TAFS IS FOR PREVAILING IFR/LIFR CONDITIONS
AT KAND, A TEMPO FOR SUCH AT KGMU, AND SCT IFR LAYERS AT KGSP. AS
FAR AS THE NC TERMINALS, STILL CAN'T RULE OUT RESTRICTIONS, BUT
IT'S BEGINNING TO LOOK LESS LIKELY, AND WILL GENERALLY LIMIT THE
IMPACT TO FEW/SCT IFR CLOUD LAYERS. SCATTERED TO NUMEROUS COVERAGE
OF SHOWERS AND THUNDERSTORMS IS EXPECTED ACROSS THE AREA THIS
AFTERNOON/EVENING IN ADVANCE OF A BACKDOOR COLD FRONT. MOST SITES
RECEIVE A PROB30 OR TEMPO FOR TSRA AT SOME POINT THIS AFTERNOON,
WITH A PERIOD OF CATEGORICAL SHRA/TSRA LATE THIS AFTERNOON INTO
EARLY EVENING. CONVECTIVE COVERAGE IS EXPECTED TO BE SLOW TO
DIMINISH OVERNIGHT, AS THE FRONT SAGS GRADUALLY SW ACROSS THE
TERMINAL FORECAST AREA. THEREFORE, MOST SITES HOLD ON TO A VCSH
THROUGH THE END OF THE PERIOD. IFR CLOUDS ARE THEN EXPECTED TO
FILL IN BEHIND THE FRONT FROM LATE EVENING THROUGH THE EARLY
MORNING HOURS, WITH MVFR VISBY ALSO BECOMING A POSSIBILITY. WINDS
WILL GENERALLY BECOME LIGHT NE BY THIS AFTERNOON, WITH NE WINDS
INCREASING TO 5-10 KTS TONIGHT THROUGH SAT MORNING.
OUTLOOK: WIDESPREAD CIG RESTRICTIONS MAY LINGER THROUGH SATURDAY
NIGHT. THE REST OF THE WEEKEND LOOKS VFR APART FROM THE USUAL LOW
STRATUS AND/OR FOG EACH MORNING. SCATTERED TO NUMEROUS SHOWERS AND
A FEW THUNDERSTORMS ARE ALSO POSSIBLE SATURDAY, MAINLY DURING THE
AFTERNOON AND EVENING. A RETURN TO MORE TYPICAL SUMMERTIME WEATHER
IS EXPECTED EARLY NEXT WEEK.
GSP WATCHES/WARNINGS/ADVISORIES
GA...HEAT ADVISORY FROM NOON TODAY TO 7 PM EDT THIS EVENING FOR
GAZ029.
NC...NONE.
SC...HEAT ADVISORY FROM NOON TODAY TO 7 PM EDT THIS EVENING FOR
SCZ011-019.
SYNOPSIS...AR
NEAR TERM...JDL
SHORT TERM...AR
LONG TERM...AR
AVIATION...JDL
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