597
FXUS62 KGSP 051527
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1127 AM EDT SAT SEP 5 2026
WHAT HAS CHANGED
INCREASED PRECIP/THUNDERSTORM CHANCES ACROSS THE REGION AND MOVED
UP THE TIMING. THREAT OF SEVERE STORMS IS INCREASING ALONG/N OF
I-40 INTO EARLY AFTERNOON.
KEY MESSAGES
1. SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS MOST OF THE FORECAST
AREA THIS AFTERNOON AND EVENING. THE RISK FOR SEVERE STORMS IS
LESS ON SUNDAY, BUT NON-ZERO. MAKE SURE YOU HAVE MULTIPLE WAYS
TO RECEIVE WARNINGS, ESPECIALLY IF YOU HAVE OUTDOOR PLANS.
2. HOT AND HUMID AGAIN TODAY WITH TRIPLE DIGIT HEAT INDEX
VALUES RETURNING EAST OF THE MOUNTAINS. A HEAT ADVISORY REMAINS
IN EFFECT TODAY FROM 11 AM TO 8 PM FOR THE SOUTHERN ZONES. MAKE
SURE TO STAY HYDRATED AND TAKE FREQUENT BREAKS IN THE SHADE OR
AIR CONDITIONING. COOLER AND LESS HUMID CONDITIONS FINALLY RETURN
BEHIND A COLD FRONT STARTING SUNDAY.
DISCUSSION
KEY MESSAGE 1: SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS MOST OF
THE FORECAST AREA THIS AFTERNOON AND EVENING. THE RISK FOR SEVERE
STORMS IS LESS ON SUNDAY, BUT NON-ZERO. MAKE SURE YOU HAVE MULTIPLE
WAYS TO RECEIVE WARNINGS, ESPECIALLY IF YOU HAVE OUTDOOR PLANS.
A STRONG COLD FRONT WILL APPROACH FROM THE NORTH THROUGH THIS
EVENING BEFORE TRACKING ACROSS THE FORECAST AREA OVERNIGHT. MOST OF
WESTERN NORTH CAROLINA AND THE NORTHERN UPSTATE ARE IN THE SLIGHT
RISK ON THE UPDATED DAY 1 CONVECTIVE OUTLOOK FROM SPC. A MARGINAL
RISK IS IN PLACE ACROSS THE REST OF THE FCST AREA.
A LINE OF THUNDERSTORMS WAS DEVELOPING LATE THIS MORNING OVER
SOUTHWEST VA AND MOVING INTO NORTHEAST TN, ON TRACK TO REACH THE
NRN MOUNTAINS BY 17Z AT THE LATEST. THE LATEST MESOANALYSIS SHOWS
THE MORNING CAP HAS LIFTED AND WE HAVE ROUGHLY 2000-3000 J/KG OF
SFC-BASED CAPE TO WORK WITH, THOUGH THE STORMS APPEAR TO BE MOVING
OUT AHEAD OF THE BETTER EFFECTIVE BULK SHEAR. WE ALSO HAVE GREATER
THAN 1000 DCAPE OUT AHEAD OF THE DEVELOPING LINE. SUFFICE TO SAY,
THIS LINE OF STORMS SHOULD PROBABLY SURVIVE THE DIURNAL MINIMUM
AND KEEP TRUCKING TO THE EAST-SOUTHEAST. PRECIP PROBS HAVE BEEN
UPDATED ALREADY TO RAISE CHANCES OVER THE AREA MAINLY ALONG/N
OF I-40. THERE IS A DISTINCT POSSIBILITY THAT WE END UP WITH A
SVR WATCH BEFORE EARLY AFTERNOON. IT REMAINS TO BE SEEN HOW THIS
ACTIVITY, OR AN OUTFLOW BOUNDARY, WILL MAINTAIN ITSELF OR TRIGGER
NEW STORMS EAST OF THE MTNS, BUT CHANCES ARE GOING UP.
THE MAIN CHANGE FOR SUNDAY (AT LEAST COMPARED TO THIS TIME
YESTERDAY) IS THAT THE DAY 2 SPC SEVERE WEATHER OUTLOOK HAS A GOOD
CHUNK OF THE GSP FORECAST AREA HIGHLIGHTED IN A SEVERE RISK. MOST
OF THE GSP FORECAST AREA IS IN A MARGINAL RISK, WITH THE EXCEPTION
OF THE NORTHERN NC MOUNTAINS, NORTHERN NC FOOTHILLS, AND NORTHERN
NC PIEDMONT WHICH ARE NOT HIGHLIGHTED FOR A SEVERE RISK. THE SLIGHT
RISK EXTENDS INTO PORTIONS OF GREENWOOD AND ABBEVILLE COUNTIES IN
SC. WITH THE FRONT EXPECTED TO BE SOUTH OF THE AREA ON SUNDAY, THE
SEVERE THREAT WOULD APPEAR TO BE LOWER COMPARED TO TODAY. GUIDANCE
HAS DEEP LAYER SHEAR DECREASING TO 15-20 KTS ON SUNDAY AND GENERALLY
2,000 J/KG OR LESS OF MLCAPE. THE BEST INSTABILITY WOULD APPEAR TO
BE ACROSS THE WESTERN AND SOUTHERN ZONES PER THE NAMNEST AND RAP.
THE MAIN HAZARD WITH ANY SEVERE STORMS THAT DEVELOP SUNDAY AFTERNOON
AND EVENING WILL BE DAMAGING WIND GUSTS BUT ISOLATED HAIL UP TO
ONE INCH IN DIAMETER CANNOT BE RULED OUT.
DRIER CONDITIONS SHOULD RETURN FOR MUCH OF NEXT WEEK AS AN UPPER
ANTICYLCONE BUILDS ACROSS THE REGION. ANOTHER COLD FRONT MAY BRING
RAIN CHANCES BACK FRIDAY.
KEY MESSAGE 2: HOT AND HUMID AGAIN TODAY WITH TRIPLE DIGIT HEAT INDEX
VALUES RETURNING EAST OF THE MOUNTAINS. A HEAT ADVISORY REMAINS
IN EFFECT TODAY FROM 11 AM TO 8 PM FOR THE SOUTHERN ZONES. MAKE
SURE TO STAY HYDRATED AND TAKE FREQUENT BREAKS IN THE SHADE OR
AIR CONDITIONING. COOLER AND LESS HUMID CONDITIONS FINALLY RETURN
BEHIND A COLD FRONT STARTING SUNDAY.
NO CHANGES TO THE HEAT ADVISORY THIS FORECAST UPDATE AS THE PRODUCT
APPEARS WELL PLACED BASED ON THE 00Z CAMS TIMING OF CONVECTION AHEAD
OF A STRONG COLD FRONT THIS AFTERNOON/EARLY EVENING. THE SOUTHERN
ZONES ARE CURRENTLY EXPECTED TO SEE A LATER ARRIVAL TIME FOR STORMS
COMPARED TO THE NORTHERN ZONES, SO THINKING IS THAT THE SOUTHERN
ZONES EAST OF THE MOUNTAINS ARE MORE LIKELY TO REACH HEAT ADVISORY
CRITERIA COMPARED TO THE NORTHERN ZONES EAST OF THE MOUNTAINS.
HOWEVER, IF THE LINE OF STORMS ENDS UP DEVELOPING EARLIER IN THE
DAY, THIS WOULD ACT TO LIMIT SOME, IF NOT ALL, OF THE SOUTHERN
ZONES FROM REACHING HEAT ADVISORY CRITERIA (WILL HAVE TO WAIT AND
SEE WHAT THE 06Z CAM TRENDS ARE LATER THIS MORNING). REGARDLESS,
WITH A MYRIAD OF OUTDOOR PLANS EXPECTED OVER THE HOLIDAY WEEKEND,
A MORE "IMPACTED-BASED" HEAT ADVISORY APPEARS WARRANTED.
COOLER AND LESS HUMID CONDITIONS FINALLY RETURN BEHIND THE FRONT
STARTING SUNDAY, WITH MONDAY STILL EXPECTED TO BE THE COOLEST DAY
IN THE FORECAST PERIOD. A WARMING TREND CAN BE EXPECTED TUESDAY
THROUGH THE AT LEAST THURSDAY AS ANOTHER UPPER ANTICYCLONE BUILDS
OVER THE SOUTHERN AND EASTERN UNITED STATES. LUCKILY, THIS DOME
OF HIGH PRESSURE LOOKS LESS HOT AND HUMID OVERALL. ANOTHER COLD
FRONT LOOKS TO BRING BACK SLIGHTLY COOLER TEMPERATURES BY LATE WEEK.
AVIATION /15Z SATURDAY THROUGH WEDNESDAY/
AT KCLT AND ELSEWHERE: DRY AND VFR THROUGH THE MORNING HOURS,
POSSIBLY EVEN THE EARLY AFTERNOON HOURS FOR SOME TERMINALS, OUTSIDE
OF MOUNTAIN VALLEY FOG AND STRATUS THAT DEVELOPED OVERNIGHT. FOG AND
STRATUS WILL LIFT SHORTLY AFTER SUNRISE. A COLD FRONT WILL BRING A
BROKEN LINE OF TSRA AND ASSOCIATED RESTRICTIONS ACROSS THE TERMINALS
THIS AFTERNOON INTO EARLY THIS EVENING SO MAINTAINED PROB30S AT KAVL
AND KAND AS CONFIDENCE IS LOWER ON THESE TERMINALS SEEING STORMS.
INTRODUCED TEMPOS ACROSS THE REST OF THE TERMINALS DUE TO HIGHER
CONFIDENCE ON STORM DEVELOPMENT. CONFIDENCE ON TIMING FOR BOTH
PROB30S AND TEMPOS IS LOW AS GUIDANCE HAS NOT BEEN CONSISTENT RUN TO
RUN REGARDING TSRA ACTIVITY. DRY AND VFR CONDITIONS SHOULD RETURN BY
EARLY OR LATE EVENING BEHIND THE FRONT. WINDS BE NW AT KAVL THROUGH
THE PERIOD. WINDS EAST OF THE MOUNTAINS WILL START OUT WSW/SW BEFORE
TOGGLING MORE WNW/NW BY LATE MORNING OR EARLY AFTERNOON. VRB WINDS
CAN THEN BE EXPECTED BY MID TO LATE AFTERNOON INTO THE LATE EVENING
HOURS. OVERNIGHT, WINDS EAST OF THE MOUNTAINS WILL TOGGLE MORE N/NE.
OUTLOOK: ANOTHER ROUND OF SHOWERS AND THUNDERSTORMS DEVELOPS SUNDAY,
POSSIBLY LINGERING INTO MONDAY. DRIER CONDITIONS RETURN BY MONDAY
NIGHT, LINGERING THROUGH MID-WEEK.
GSP WATCHES/WARNINGS/ADVISORIES
GA...HEAT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR GAZ026-028-029.
NC...HEAT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR NCZ071-072-082.
SC...HEAT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR SCZ009>014-019.
AR/PM
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