974
FXUS62 KGSP 221038
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
638 AM EDT WED JUL 22 2026
WHAT HAS CHANGED
UPDATED THE AVIATION DISCUSSION FOR THE 12Z TAFS.
KEY MESSAGES
1. VERY ACTIVE CONVECTIVE WEATHER IS EXPECTED THROUGH THE END
OF THE WEEK, AS A FRONTAL BOUNDARY MOVES INTO THE AREA AND
STALLS. ISOLATED SEVERE STORMS ARE POSSIBLE THIS AFTERNOON AND
EVENING, WITH AN ESCALATING RISK OF HEAVY RAINFALL AND POTENTIALLY
FLASH FLOODING FROM TONIGHT THROUGH AT LEAST FRIDAY.
2. A RETURN TO TYPICAL LATE JULY WEATHER IS EXPECTED NEXT WEEK.
DISCUSSION
KEY MESSAGE 1: VERY ACTIVE CONVECTIVE WEATHER IS EXPECTED THROUGH THE
END OF THE WEEK, AS A FRONTAL BOUNDARY MOVES INTO THE AREA AND
STALLS. ISOLATED SEVERE STORMS ARE POSSIBLE THIS AFTERNOON AND
EVENING, WITH AN ESCALATING RISK OF HEAVY RAINFALL AND POTENTIALLY
FLASH FLOODING FROM TONIGHT THROUGH AT LEAST FRIDAY.
A SLOW MOVING FRONTAL ZONE WILL SETTLE OVER THE AREA TODAY AND
STALLING NEAR THE AREA ON THURSDAY AS A COUPLE OF SHORT WAVES ROTATE
THROUGH AN UPPER TROUGH DEVELOPING OVER THE EAST COAST. THIS WILL
LEAD TO INCREASED FORCING AND AN INCREASE IN BULK SHEAR. CONVECTION
WILL BE SLOWER TO START THAN USUAL, MAINLY LATE AFTERNOON INTO THE
EVENING AND STORMS WILL BE SLOW TO MOVE SOUTH ACROSS THE AREA. THE
AIR MASS REMAINS MOIST AND UNSTABLE, BUT MID-LEVEL LAPSE RATES WILL
BE MEAGER. STILL, THE LOW-LEVEL LAPSE RATES MAY INCREASE ENOUGH WITH
DAYTIME HEATING FOR AN ISOLATED SEVERE STORM WITH DAMAGING WINDS.
THE BIGGER CONCERN WILL END UP BEING THE POTENTIAL FOR HEAVY
RAINFALL AS PERIODS OF THUNDERSTORMS CROSS THE AREA ALONG AND NEAR
THE STALLED FRONTAL BOUNDARY THROUGH FRIDAY. PW VALUES ARE FORECAST
TO SURGE TO 2" (OR MORE) OVER THE AREA WITHIN DEEP SW FLOW, AND
FORECAST SOUNDINGS DEPICT VERY DEEP WARM CLOUD DEPTHS OF OVER 12
KFT, ALONG WITH NOTABLE INSTABILITY LINGERING WELL PAST THE TYPICAL
DIURNAL CYCLE. WITH MEAN CLOUD-BEARING WINDS OF 20 KTS OR MORE
EXPECTED, CELL MOVEMENT WILL BE RELATIVELY FAST. HOWEVER, THE MEAN
FLOW WILL BE ORIENTED ALMOST PERFECTLY PARALLEL TO THE BOUNDARY,
CREATING THE THREAT FOR TRAINING, HIGHLY EFFICIENT RAINFALL-
PRODUCING CELLS. THAT SAID, UNCERTAINTY REMAINS REGARDING THE BEST
LOCATION FOR TRAINING CELLS AS THE GUIDANCE CONTINUES TO FAVOR
DIFFERENT LOCATIONS. THE RESULTING QPF ALSO VARIES IN AMOUNTS AND
LOCATIONS. GIVEN THIS UNCERTAINTY, WILL HOLD OFF ON ISSUING A FLOOD
WATCH AT THIS TIME. PREFER TO WAIT FOR SOME CONSOLIDATION IN THE
GUIDANCE TO TARGET THE MAIN THREAT AREAS INSTEAD OF ISSUING A
FORECAST AREA-WIDE WATCH THAT REMAINS IN EFFECT FOR DAYS.
THE BOUNDARY IS FORECAST TO REMAIN OVER, OR NEAR OUR AREA THROUGH AT
LEAST FRIDAY, BUT HIGH PRESSURE BUILDING INTO THE NORTHEAST CONUS
WILL TRY TO NUDGE THE BOUNDARY SOUTH OF THE CWA. THUS, MORE STABLE
AIR WILL GRADUALLY FILTER INTO THE AREA WITH TIME. THE POTENTIAL FOR
HEAVY RAINFALL AND ISOLATED FLASH FLOODING WILL NEVERTHELESS
CONTINUE INTO THURSDAY, AS THE POTENTIAL FOR TRAINING, HIGHLY
EFFICIENT RAIN SHOWERS AND STORMS WILL CONTINUE. THIS THREAT SHOULD
GRADUALLY RELENT TOWARD THE WEEKEND AS THE BOUNDARY SETTLES FARTHER
SOUTH. AFTER A DAY OF NEAR-NORMAL HEAT TODAY, MAX TEMPERATURES ARE
FORECAST TO COOL TO WELL-BELOW NORMAL LEVELS THU THROUGH SAT UNDER
THE INFLUENCE OF COOLING EASTERLY FLOW, ANOMALOUSLY LOW HEIGHTS, AND
WIDESPREAD CLOUD COVER.
KEY MESSAGE 2: A RETURN TO TYPICAL LATE JULY WEATHER IS EXPECTED
NEXT WEEK.
THE GLOBAL MODELS LARGELY AGREE THAT DEEP-LAYER DRYING WILL
OCCUR ACROSS THE REGION BY SUNDAY, THUS BRINGING AN END TO THE
PERIOD OF RELATIVELY COOL AND VERY ACTIVE CONVECTIVE WEATHER
THAT IS ANTICIPATED LATE THIS WEEK. FORECAST TEMPS RETURN TO NEAR-
NORMAL SUNDAY, THEN ABOVE NORMAL EARLY NEXT WEEK. CONVECTION IS
STILL IN THE FORECAST EACH DAY SUNDAY-TUESDAY, BUT POPS ARE MAINLY
IN THE 20-30% RANGE AND TIMING OF SAID POPS IS LARGELY TIED TO THE
DIURNAL HEATING CYCLE.
AVIATION /12Z WEDNESDAY THROUGH SUNDAY/
AT KCLT AND ELSEWHERE: VFR WITH LOW END GUSTY S TO SW WIND. A
SPOTTY SHOWER IS POSSIBLE AT KAVL OR KHKY.
THE GUIDANCE SHOWS BETTER CHANCES OF CONVECTION SLIDING SOUTH TO THE
TAF SITES DURING THE AFTERNOON. HAVE TIMED PROB30S BASED ON THE
TIMING OF THE CONVECTION MOVING SOUTHWARD. S TO SW WIND SHOW MORE
STEADY GUSTS BY AFTERNOON. THE POTENTIAL FOR CONVECTION LINGERS
OVERNIGHT AS A COLD FRONT DROPS INTO THE AREA. HAVE GONE WITH -SHRA
AND PROB30S FOR THE CONTINUING CONVECTIVE CHANCES. GUSTS END AND
WIND SPEEDS DIMINISH DURING EVENING OUTSIDE OF TSRA. MVFR CIGS
DEVELOP OVERNIGHT ALONG WITH SOME MVFR VSBY.
OUTLOOK: ACTIVE FORECAST TO CONTINUE WITH POTENTIAL FOR CONVECTION
THROUGH THE WEEKEND, AS A COLD FRONT STALLS IN OR NEAR THE TERMINAL
FORECAST AREA. LOW STRATUS AND/OR FOG WILL BE POSSIBLE EACH
MORNING, ESPECIALLY IN THE MOUNTAIN VALLEYS AND LOCATIONS WHICH
RECEIVE ESPECIALLY HEAVY RAINFALL.
GSP WATCHES/WARNINGS/ADVISORIES
GA...NONE.
NC...NONE.
SC...NONE.
RWH
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