537
FXUS62 KGSP 271041
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
641 AM EDT SAT JUN 27 2026
WHAT HAS CHANGED
UPDATED THE AVIATION DISCUSSION FOR THE 12Z TAFS.
KEY MESSAGES
1. SHOWER AND THUNDERSTORM CHANCES LINGER THROUGH THE
WEEKEND. ISOLATED SEVERE STORMS CAPABLE OF PRODUCING DAMAGING
WIND GUSTS ARE POSSIBLE THIS AFTERNOON/EVENING.
2. HEAT RISK WILL INCREASE THROUGH AT LEAST MIDWEEK, WITH HEAT
INDICES POTENTIALLY EXCEEDING 100 DEGREES ACROSS MUCH OF THE
PIEDMONT AND FOOTHILLS.
DISCUSSION
KEY MESSAGE 1: SHOWER AND THUNDERSTORM CHANCES LINGER THROUGH THE
WEEKEND. ISOLATED SEVERE STORMS CAPABLE OF PRODUCING DAMAGING WIND
GUSTS ARE POSSIBLE THIS AFTERNOON/EVENING.
MOSTLY ZONAL FLOW ALOFT WITH A SURFACE BOUNDARY DRAPED TO THE NORTH
WILL ALLOW FOR A MOIST AND UNSTABLE ENVIRONMENT TO GET UNDERWAY
AS A WEAK SHORTWAVE SHIFTS ACROSS THE CWFA DURING THE DAYTIME
PERIOD. DEWPOINTS IN THE LOW 70S WILL LEAD TO GOOD DESTABILIZATION
(1500-2500 J/KG SBCAPE) WITH SCATTERED TO NUMEROUS SHOWERS AND
THUNDERSTORMS EXPECTED TO THE DEVELOP. A FEW STORMS ARE LIKELY
TO BECOME STRONG TO SEVERE AS STEEP LOW-LEVEL LAPSE RATES AND
VERY MODEST LOW-LEVEL SHEAR WILL AID IN THE DEVELOPMENT OF STORM
CLUSTERING CAPABLE OF DAMAGING WINDS. CAMS HAVE BEEN FIXATED ON
WESTERN NC, BUT THIS THREAT WILL EXTEND INTO NORTHEAST GA AND
UPSTATE SC WITH LESS CONVECTIVE COVERAGE EXPECTED COMPARED TO
NC. OVERALL TIMING IS EXPECTED BETWEEN 2 PM AND MIDNIGHT TONIGHT,
WITH MULTIPLE ROUNDS OF SEVERE WEATHER BEING POSSIBLE THROUGHOUT
THAT TIME PERIOD. THE SEVERE THREAT SHOULD WANE AFTER MIDNIGHT WITH
THE LOSS OF INSTABILITY, BUT LINGERING SHOWERS AND THUNDERSTORMS
CAN'T BE RULED OUT DURING THE OVERNIGHT PERIOD. AFTERNOON HIGHS
ARE EXPECTED TO BE AT OR SLIGHTLY ABOVE NORMAL.
ANOTHER ROUND OF CONVECTION IS POSSIBLE ON SUNDAY AS A DEEPENING
UPPER/MID-LEVEL ANTICYCLONE FORMS OVER THE LOWER/MID-MS VALLEY. THIS
WILL PLACE THE AREA IN THE "RING OF FIRE" WITH NORTHWESTERLY FLOW
ALOFT BECOMING ESTABLISHED AS CONVECTION MOVES DOWNSTREAM FROM THE
TOP OF THE RIDGE AXIS. TIMING AND LOCATIONS BEING IMPACTED HAVE BEEN
VARIABLE VIA CAMS AND DETERMINISTIC MODELS, BUT LINGERING CONVECTIVE
DEBRIS AND THE POTENTIAL FOR THE ATMOSPHERE TO BE OVERTURNED FROM
SATURDAY'S CONVECTION SHOULD LIMIT THE OVERALL SEVERE THREAT. IN
THIS TYPE OF SETUP, THE TYPICAL DIURNAL TIME LINE DOESN'T PLAY A
ROLE FOR WHEN POTENTIAL DECAYING MCSS MOVE ACROSS PORTIONS OF THE
CWFA, BUT CAN DETERMINE THE SEVERITY IF A CLUSTER OF STORMS MOVES
INTO THE AREA DURING PEAK HEATING. WILL BE SOMETHING TO MONITOR,
ESPECIALLY AFTER TODAY'S EXPECTED SEVERE THREAT. AFTERNOON HIGHS
WILL ALSO BE VARIABLE ON SUNDAY AS CONVECTIVE DEBRIS AND DAYBREAK
STRATUS COULD KEEP TEMPERATURES FROM REACHING THE CURRENT FORECASTED
MAX TEMPERATURES.
KEY MESSAGE 2: HEAT RISK WILL INCREASE THROUGH AT LEAST MIDWEEK,
WITH HEAT INDICES POTENTIALLY EXCEEDING 100 DEGREES ACROSS MUCH
OF THE PIEDMONT AND FOOTHILLS.
DEEPENING UPPER/MID-LEVEL ANTICYCLONE WILL SET UP SHOP OVER
THE LOWER/MID-MS VALLEY THIS WEEKEND INTO EARLY NEXT WEEK, WHILE
PROPAGATING EASTWARD THROUGH MID-WEEK. MOST OF THE GUIDANCE PLACES
THE CLOSED UPPER RIDGE OVER THE EASTERN CONUS BY MID-WEEK, WHICH
WILL ALLOW AFTERNOON HIGHS TO UPTICK INTO THE MID 90S BY WEDNESDAY,
WITH SOME LOCATIONS POSSIBLY GETTING INTO THE UPPER 90S. DRIER
AIR ALOFT AND LOW-LEVEL SUBSIDENCE SHOULD HELP DEWPOINTS MIX OUT
DURING PEAK HEATING EACH AFTERNOON, BUT MAY NOT BE ENOUGH TO FORGO
HEAT PRODUCTS AS THE CONCERN FOR MULTIPLE DAYS OF HEAT INDICES OF
100+ DEGREES BECOMES REALIZED BY MID TO LATE WEEK. THIS SYNOPTIC
SETUP WILL ALSO HELP TO SUPPRESS CONVECTIVE INITIATION AS ANY
AFTERNOON/EVENING CONVECTION WILL LIKELY REMAIN OVER THE HIGHER
TERRAIN. GUIDANCE KEEPS THE RIDGE INTACT THROUGH AT LEAST D7,
MEANING THE MULTI-DAY HEAT EVENT COULD LINGER INTO THE INDEPENDENCE
DAY HOLIDAY WEEKEND AS THERE ISN'T A STRONG SIGNAL FOR RELIEF FROM
THE HEAT.
THOSE WITH OUTDOOR PLANS, INCLUDING HOLIDAY AND RECREATION, SHOULD
PREPARE FOR SEVERAL DAYS OF ELEVATED HEAT RISK. STAY HYDRATED,
TAKE FREQUENT BREAKS IN AIR-CONDITIONED OR SHADED AREAS, AND NEVER
LEAVE CHILDREN OR PETS UNATTENDED IN VEHICLES.
AVIATION /12Z SATURDAY THROUGH WEDNESDAY/
AT KCLT AND ELSEWHERE: MOSTLY VFR CONDITIONS EXPECTED THROUGH
THE FORECAST PERIOD. LINGERING MID-LEVEL CLOUD COVER STICKS AROUND
THROUGH AT LEAST DAYBREAK AS LIGHT SOUTH TO SOUTHWESTERLY WINDS
CONTINUE. MVFR/IFR FOG AND LOW STRATUS HAS DEVELOPED IN PORTIONS OF
THE AREA, MAINLY IN LOCATIONS THAT RECEIVED RAINFALL YESTERDAY
EVENING. INCLUDED A TEMPO MENTION FOR MVFR VSBY AT KHKY AS A RESULT.
SCATTERED SHOWERS AND THUNDERSTORMS ARE LIKELY THIS AFTERNOON AND
EVENING AND TIMED THIS OUT USING A PROB30 AT ALL TAF SITES FOR TSRA
AND ASSOCIATED RESTRICTIONS. CONFIDENCE IS SLIGHTLY HIGHER FOR KAVL
AND KCLT AND PLACED A TEMPO MENTION TO INDICATE THE HIGHER CHANCES.
LOW-END GUSTS OUT OF THE SOUTH TO SOUTHWEST ARE EXPECTED DURING THE
AFTERNOON AT 15-20 KTS. GUIDANCE HAS HINTED AT POSSIBLE OVERNIGHT
STRATUS WITH MVFR POTENTIAL AND INCLUDED A MVFR CIG AT ALL TAF SITES
STARTING JUST BEFORE DAYBREAK. THERE IS ALSO SOME INDICATION OF
SHOWERS AND THUNDERSTORMS CONTINUING INTO THE OVERNIGHT PERIOD.
CONFIDENCE IS TOO LOW FOR A TAF MENTION AT THIS TIME, BUT SOMETHING
THAT WILL NEED TO BE MONITORED THROUGHOUT THE DAYTIME PERIOD.
OUTLOOK: DAILY CHANCES FOR SHOWERS AND THUNDERSTORMS, AS WELL
AS ASSOCIATED RESTRICTIONS, WILL LINGER THROUGH EARLY NEXT
WEEK. MOUNTAIN VALLEY FOG/LOW STRATUS WILL POSSIBLE EACH MORNING.
GSP WATCHES/WARNINGS/ADVISORIES
GA...NONE.
NC...NONE.
SC...NONE.
CAC
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