932
FXUS62 KGSP 211019
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
619 AM EDT MON SEP 21 2026
WHAT HAS CHANGED
UPDATED THE AVIATION DISCUSSION FOR THE 12Z TAF ISSUANCE.
KEY MESSAGES
1. A FEW SEVERE THUNDERSTORMS ARE POSSIBLE TODAY AND TUESDAY,
MAINLY IN THE LATE AFTERNOON AND EARLY EVENING. THE PRIMARY
CONCERNS FROM ANY STRONGER STORMS WILL BE DAMAGING WIND GUSTS
AND EXCESSIVE RAINFALL.
2. A COOL-DOWN IS EXPECTED BY MID-WEEK THAT SHOULD KEEP
TEMPERATURES BELOW NORMAL THROUGH THE WEEKEND.
DISCUSSION
KEY MESSAGE 1: A FEW SEVERE THUNDERSTORMS ARE POSSIBLE TODAY AND
TUESDAY, MAINLY IN THE LATE AFTERNOON AND EARLY EVENING. THE
PRIMARY CONCERNS FROM ANY STRONGER STORMS WILL BE DAMAGING WIND
GUSTS AND EXCESSIVE RAINFALL.
CONDITIONS WILL REMAIN UNSETTLED OVER THE NEXT COUPLE OF DAYS AS
FLAT UPPER RIDGING CENTERED OVER THE SOUTHERN PLAINS CONTINUES TO
INTERACT WITH A WEAK UPPER LOW OVER THE FL PENINSULA AND EASTERN
GULF. THIS UPPER PATTERN COUPLED WITH A VERY BROAD REGION OF LOW-
LEVEL CONVERGENCE, WILL HELP KEEP AMPLE DEEP-LAYER MOISTURE OVER
THE SOUTHEAST AND FUEL DIURNAL SHOWERS AND THUNDERSTORMS THIS AFTN
AND EVENING. MOST OF THE NEAR-TERM GUIDANCE CONTINUES TO SUGGEST
THAT CONVECTIVE ACTIVITY WILL INITIATE OVER THE NC MOUNTAINS THIS
AFTERNOON AND THEN SPREAD S/SE AS THE DAY/EVENING PROGRESSES. THE
SEVERE RISK IS STILL LOOKING MARGINALLY HIGHER TODAY AS COMPARED TO
THE PAST FEW DAYS, AS SFC-BASED CAPE WILL LIKELY BE GREATER ACROSS
MOST OF OUR CWA THIS AFTERNOON/EVENING. IN ADDITION, GREATER AMOUNTS
OF DCAPE ARE ALSO EXPECTED ACROSS OUR AREA WHICH SHOULD HELP PRODUCE
STRONGER DOWNDRAFTS. SOME OF THE LATEST CAM RUNS CONTINUE TO PRODUCE
SOME CLUSTERING OF STORMS NEAR THE BLUE RIDGE ESCARPMENT THIS AFTER-
NOON ONCE THE WEAK CAP IS BROKEN, WITH STORMS THEN MOVING SOUTH AND
EAST LARGELY ON COLD POOLS. WITH THE WEAK STEERING FLOW ALOFT, STORMS
WILL BE MOVING SLOWLY, THUS INCREASING THE THREAT FOR LOCALIZED FLASH
FLOODING TODAY AND TONIGHT. THE SEVERE THREAT FOR TUESDAY STILL APPEARS
LOWER, BUT IT WILL LARGELY DEPEND ON THE AMOUNT OF CLOUD COVER ACROSS
OUR CWA TUESDAY MORNING AND HOW QUICKLY AN ELY LOW-LEVEL FLOW DEVELOPS.
MOST OF THE LATEST OPERATIONAL MODELS HAVE LITTLE IN THE WAY OF A COLD-
AIR DAMMING WEDGE DEVELOPING EAST OF THE MTNS UNTIL EARLY WEDNESDAY.
THE RESULT IS MORE INSTABILITY ACROSS MUCH OF OUR FCST AREA ON TUESDAY.
ALTHOUGH THE SEVERE THREAT SHOULD BE LOWER ON TUESDAY, WE CAN EXPECT
GREATER COVERAGE OF SHOWERS AND STORMS TUESDAY AFTERNOON AND EVENING
WITH A HIGHER RISK FOR LOCALIZED FLOODING. AS FOR TEMPERATURES, HIGHS
ARE EXPECTED TO REACH 90+ DEGREES AT MOST LOCATIONS OUTSIDE THE MTNS
TODAY. VALUES WILL MODERATE SOMEWHAT ON TUESDAY, BUT THEY HAVE BEEN
TRENDING WARMER OVER THE PAST FEW FCST CYCLES WITH MOST OF OUR CWA
REMAINING ROUGHLY 3 TO 6 DEGREES ABOVE NORMAL.
KEY MESSAGE 2: A COOL-DOWN IS EXPECTED BY MID-WEEK THAT SHOULD KEEP
TEMPERATURES BELOW NORMAL THROUGH THE WEEKEND.
ON TUESDAY, THE NORTHERN STREAM BECOMES MORE BLOCKY OVER THE CENTRAL
CONUS AS A MID/UPPER LOW SLIDES UNDERNEATH STOUT UPPER RIDGING. THIS
RESULTS IN A REX-TYPE BLOCKING PATTERN CENTERED TO OUR NORTH BY MID-
WEEK. THE UPPER LOW IS EXPECTED TO STRENGTHEN/AMPLIFY TOWARDS THE END
OF THE WEEK AND BEGIN TO MOVE OFFSHORE OVER THE WEEKEND. AT THE SFC,
CYCLOGENESIS OFF THE MID-ATLANTIC COAST IS EXPECTED TO BRING A BACK-
DOOR COLD FRONT SOUTHWARD AND THRU OUR FCST AREA ON TUESDAY. AT THE
SAME TIME, VERY BROAD SFC HIGH PRESSURE WILL PARK ITSELF TO OUR NORTH
OVER ONTARIO AND QUEBEC HELPING TO ESTABLISH A COLD-AIR DAMMING WEDGE
ON WEDNESDAY THAT WILL LIKELY PERSIST THRU THE END OF THE WEEK. THE
RESULTING COOL NELY FLOW AND SHOWER POTENTIAL WILL HELP KEEP TEMPERA-
TURES ABOUT 8 TO 12 DEGREES BELOW NORMAL THRU FRIDAY. THE WEDGE WILL
LIKELY WEAKEN ON FRIDAY AS THE SFC LOW LIFTS FURTHER NE AND DRIER AIR
WORKS ITS WAY INTO OUR AREA FROM THE WEST. NONETHELESS, TEMPERATURES
ARE EXPECTED TO REMAIN BELOW NORMAL THRU THE WEEKEND WITH SHOWER CHANCES
DIMINISHING EACH DAY FROM THURSDAY ONWARD AND INCREASING SUNSHINE.
AVIATION /10Z MONDAY THROUGH FRIDAY/
AT KCLT AND ELSEWHERE: WINDS REMAIN LIGHT AND VRB THROUGH THE PERIOD
ACROSS ALL TERMINALS. BR/FG AT KAVL/KHKY DISSIPATES AFTER 13Z, SO
PREVAILING 1/2-1SM OF VSBY. VFR RETURNS AFTER SUNRISE WITH TSRA
POSSIBLE AT ALL SITES THIS AFTERNOON, PROMPTING ANOTHER ROUND OF
PROB30S THAT LINGER PAST 00Z. VFR CIGS AND CALM/VRB WINDS RETURN
AFTER 00Z. MOUNTAIN SITES KAVL/KHKY GO CALM OVERNIGHT WITH IFR/LIFR
BR/FG RETURNING AFTER 08Z. MVFR CIGS FOR KCLT TOWARD 10Z AND REMAINS
IN PLACE THROUGH LATE MORNING.
OUTLOOK: SHOWER AND THUNDERSTORM CHANCES CONTINUE EACH AFTERNOON
THROUGH TUESDAY. PATTERN CHANGE AFTER TUESDAY COULD BRING IN
VSBY/CIG RESTRICTIONS. MOUNTAIN VALLEY FOG AND LOW STRATUS POSSIBLE
EACH MORNING.
GSP WATCHES/WARNINGS/ADVISORIES
GA...NONE.
NC...NONE.
SC...NONE.
CP/JPT
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