829
FXUS62 KGSP 040313
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1113 PM EDT THU SEP 3 2026
WHAT HAS CHANGED
UPDATED THE AVIATION FORECAST FOR THE 00Z TAF ISSUANCE.
KEY MESSAGES
1. HOT AND HUMID CONDITIONS PERSIST THROUGH SATURDAY, WITH
EXPECTED HEAT INDEX VALUES IN THE LOWER 100S MOST PLACES EAST OF
THE MOUNTAINS EACH AFTERNOON.
2. SEVERE THUNDERSTORM RISK WILL INCREASE ON SATURDAY AFTERNOON
AS A STRONG COLD FRONT APPROACHES.
DISCUSSION
KEY MESSAGE 1: HOT AND HUMID CONDITIONS PERSIST THROUGH SATURDAY,
WITH EXPECTED HEAT INDEX VALUES IN THE LOWER 100S MOST PLACES EAST
OF THE MOUNTAINS EACH AFTERNOON.
A TYPICAL HOT SUMMERTIME PATTERN WILL PERSIST THROUGH FRIDAY,
FEATURING A LARGE UPPER ANTICYCLONE. THE ANTICYCLONE SHOULD STICK
AROUND THROUGH TONIGHT, BUT ON FRIDAY CHANGES WILL BE UNDERWAY AS AN
UPPER LEVEL BLOCKING PATTERN AMPLIFIES OVER NORTH AMERICA. FROM
FRIDAY INTO FRIDAY NIGHT, THE PATTERN CHANGE SHOULD MOVE/RELOCATE
THE ANTICYCLONE TO THE PLAINS, BUT NOT FAST ENOUGH TO PREVENT ONE
MORE POTENTIALLY HOT DAY ON SATURDAY, DEPENDING ON THE TIMING OF A
STRONG COLD FRONT. MORE ON THAT LATER.
FCST HIGH TEMPS FOR FRIDAY LOOK VERY SIMILAR TO WHAT WE SAW TODAY,
MEANING A CONTINUATION OF HIGHS ON THE ORDER OF 10-15 DEGREES ABOVE
NORMAL, WHILE THE DEWPOINT SHOULD REMAIN IN THE UPPER 60S AND LOWER
70S. THE DEWPOINT IS THE TRICKY PART OF THE FCST AS IT HAS MIXED OUT
LOWER THAN FCST FOR THE PAST FEW DAYS. NO REASON TO THINK THAT IT
WON'T MIX OUT AGAIN ON FRIDAY AFTERNOON, SO SOME OF THE DRIER RAW
MODEL GUIDANCE WAS BLENDED WITH THE NBM TO DROP THE DEWPOINT DOWN TO
PROBABLY MORE REASONABLE LEVELS. THIS HAS THE EFFECT OF LOWERING THE
HEAT INDEX DOWN A FEW DEGREES AND KEEPS IT BELOW HEAT ADVISORY
CRITERIA FOR ALL BUT A FEW SPOTS AROUND METRO CHARLOTTE. THE GENERAL
IDEA HERE IS THAT CONFIDENCE IS LOW AT THIS TIME THAT WE WOULD NEED
AN ADVISORY FOR FRIDAY AFTERNOON. SATURDAY IS MORE PROBLEMATIC
BECAUSE THE TEMPS WILL BE MORE LIKELY TO BE AFFECTED BY OUTFLOW
BOUNDARIES AND THE TIMING OF CONVECTION, BUT IN THE ABSENCE OF
THOSE, THE AIR MASS REMAINS HOT AND CAPABLE OF MAKING 10 DEGREES
ABOVE NORMAL. THE DEWPOINTS SHOULD BE HIGHER, THOUGH, SO HEAT
ADVISORY CRITERIA WOULD BE MORE ATTAINABLE.
AT ANY RATE, TEMPS SHOULD COOL BACK DOWN TO AROUND NORMAL FOR
THE FIRST HALF OF NEXT WEEK AS WE COME UNDER THE INFLUENCE OF
THE CYCLONIC UPPER FLOW AROUND THE UPPER LOW OFF THE CANADIAN
MARITIMES. ALAS, THE BLOCKING PATTERN COMES UNDONE AND PROGRESSIVE
FLOW WILL BRING THE HEAT BACK LATER NEXT WEEK.
KEY MESSAGE 2: SEVERE THUNDERSTORM RISK WILL INCREASE ON SATURDAY
AFTERNOON AS A STRONG COLD FRONT APPROACHES.
DEEP CONVECTION IS EXPECTED TO REMAIN RELATIVELY ISOLATED AND
CONFINED TO THE HIGHER TERRAIN AGAIN FRIDAY AFTERNOON. WILL ADD A
SLIGHT CHANCE TO THE NORTHWEST PIEDMONT IN DEFERENCE TO THE DAY 2
CONVECTIVE OUTLOOK WHICH BRUSHES THE MARGINAL RISK ACROSS THAT AREA.
THUNDERSTORM CHANCES ARE CERTAINLY MUCH HIGHER FARTHER TO THE NORTH,
BUT THERE IS SOME SMALL CHANCE THAT SOMETHING COULD ARRIVE LATE IN
THE DAY ON AN OUTFLOW BOUNDARY FROM THE CONVECTION MOVING PAST WELL
TO OUR NORTH.
WHICH BRINGS US TO SATURDAY. SEEMS LIKE A LOT OF HEAT WAVES (IF
THAT'S WHAT YOU WANT TO CALL THE LAST SEVERAL DAYS) END WITH A
BANG. THE DAY 3 CONVECTIVE OUTLOOK FROM THE SPC SHOWS A SLIGHT RISK
ACROSS MUCH OF THE FCST AREA, AND THAT IS CERTAINLY WARRANTED. AS
WE COME MORE UNDER THE CYCLONIC INFLUENCE OF THE UPPER LOW OVER
THE CANADIAN MARITIMES, A COLD FRONT SHOULD DROP DOWN FROM THE
NORTHWEST, POSSIBLY WITH IDEAL TIMING DURING PEAK HEATING. THE 15Z
RAP LOOKS COMPELLING AT 18Z SATURDAY, SHOWING AN ENVIRONMENT WITH
UPWARDS OF 3500 J/KG OF MUCAPE AND 20-30 KT OF EFFECTIVE/DEEP
LAYER SHEER TO GO ALONG WITH AN EXCELLENT TRIGGER. CONVECTION
MOVING PAST TO THE NORTH MAY ALSO LEAVE BEHIND AN OLD OUTFLOW
OR CLOUDY/CLEAR BOUNDARY TO BE A FOCUS FOR AFTERNOON STORMS. THE
EVENT REMAINS TANTALIZINGLY JUST OUTSIDE THE WINDOW OF THE CAMS, SO
CONFIDENCE IS KEPT LOW, BUT WE EAGERLY AWAIT LATER RUNS TO PROVIDE
MORE CLARITY. SHOULD BE QUIET AFTER THE FRONT PASSES SATURDAY NIGHT.
AVIATION /03Z FRIDAY THROUGH TUESDAY/
AT KCLT AND ELSEWHERE: EXPECT THE MOSTLY DRY, VFR CONDITIONS TO
CONTINUE THRU THE 00Z TAF PERIOD. FOG/LOW STRATUS WILL LIKELY
DEVELOP AGAIN IN THE USUAL MTN VALLEYS OVERNIGHT. MOST OF THE
LATEST GUIDANCE SUGGESTS THAT KAVL WILL BE IMPACTED, THUS I
KEPT PREVAILING MVFR RESTRICTIONS IN THE TAF BEGINNING AROUND
07Z, WITH A TEMPO FOR IFR FROM 09 TO 12Z. ANY RESTRICTIONS
SHOULD DISSIPATE BY 13Z OR SO TOMORROW MORNING. OTHERWISE,
POPS REMAIN TOO LOW TO MENTION SHOWERS AND/OR THUNDERSTORMS
AT ANY TAF SITES TOMORROW. ISOLATED TO SCT DIURNAL CONVECTION
IS EXPECTED TO DEVELOP OVER THE NC MTNS, BUT POPS ARE CURRENTLY
LESS THAN 30% AT KAVL. WINDS ARE EXPECTED TO GO LIGHT AND VRB
TO CALM AT MOST SITES TONIGHT. THEY WILL EVENTUALLY PICK UP
FROM THE S/SW TOMORROW AFTERNOON. AT KAVL, WINDS ARE EXPECTED
TO REMAIN LIGHT AND VRB TO CALM THRU THE TAF PERIOD.
OUTLOOK: MORE WIDESPREAD SHOWERS AND STORMS ARE EXPECTED OVER
THE WEEKEND AS A COLD FRONT CROSSES THE AREA. MORE SUPPRESSED
WEATHER RETURNS EARLY NEXT WEEK.
GSP WATCHES/WARNINGS/ADVISORIES
GA...NONE.
NC...NONE.
SC...NONE.
AR/JPT/PM
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