899
FXUS62 KGSP 181853
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
253 PM EDT TUE AUG 18 2026
WHAT HAS CHANGED
UPDATED KEY MESSAGE 2.
KEY MESSAGES
1. RELATIVELY QUIET WEATHER WILL CONTINUE THROUGH WEDNESDAY, WITH
VERY LOW CHANCES FOR AFTERNOON SHOWERS AND THUNDERSTORMS. HOT
AND MUGGY CONDITIONS WILL PERSIST.
2. AFTERNOON SHOWERS AND THUNDERSTORM CHANCES RETURN THURSDAY
AND PERSIST THROUGH SATURDAY. LOWER HUMIDITY AND NEAR-NORMAL
TEMPERATURES RETURN SUNDAY AND MONDAY.
DISCUSSION
KEY MESSAGE 1: RELATIVELY QUIET WEATHER WILL CONTINUE THROUGH
WEDNESDAY, WITH VERY LOW CHANCES FOR AFTERNOON SHOWERS AND
THUNDERSTORMS. HOT AND MUGGY CONDITIONS WILL PERSIST.
OUR REGION WILL REMAIN UNDER WEAKLY CYCLONIC UPPER FLOW THROUGH
THE MIDWEEK PERIOD. TEMPERATURES AND DEWPOINTS ARE RUNNING SLIGHTLY
LOWER THIS AFTERNOON THAN THEY WERE ON MONDAY, KEEPING HEAT INDEX
OUT OF HEAT ADVISORY RANGE. THAT SAID, IT WILL REMAIN MUGGY EVEN
FOR AUGUST. A WEAK CAPPING LAYER REMAINS ABOVE THE PBL, AND THE
LOWER TEMPS/DEWPOINTS ALSO SHOULD HAVE THE EFFECT OF INHIBITING
DEEP CONVECTION OVER THE AREA THIS AFTERNOON. WITH ABUNDANT CUMULUS
HOWEVER A STRAY/BRIEF SHOWER IS NOT OUT OF THE QUESTION IN THE LEE
OF THE BLUE RIDGE ESCARPMENT, ALTHOUGH THE OVERALL CHANCE IS ONLY
ABOUT 10%. GENERALLY NORTHERLY LOW-LEVEL FLOW WILL CONTINUE INTO
WEDNESDAY WHICH MAY BRING DEWPOINTS SLIGHTLY LOWER STILL. THUS THE
COVERAGE OF AFTERNOON CUMULUS IS EXPECTED TO BE A LITTLE LOWER
AND POPS REMAIN NEAR ZERO, AND THE AFTERNOON MAY FEEL SLIGHTLY
LESS OPPRESSIVE.
KEY MESSAGE 2: AFTERNOON SHOWERS AND THUNDERSTORM CHANCES RETURN
THURSDAY AND PERSIST THROUGH SATURDAY. LOWER HUMIDITY AND
NEAR-NORMAL TEMPERATURES RETURN SUNDAY AND MONDAY.
UPPER FLOW WILL TURN MORE CYCLONIC OVER THE INLAND PORTION OF
THE EASTERN CONUS WEDNESDAY, AS A VORT LOBE ROUNDS THE EMBEDDED
CLOSED LOW NEAR JAMES BAY. A COLD FRONT WILL ADVANCE ACROSS THE
OHIO VALLEY WEDNESDAY NIGHT IN CONJUNCTION WITH THE VORT LOBE
AND MAY SUPPORT DEVELOPMENT OF AN MCS TO OUR WEST, AND IF SO THAT
COULD MAKE A RUN AT THE APPALACHIANS THURSDAY MORNING. REGARDLESS,
850MB WAA AND LOW LEVEL MOISTURE ADVECTION STRENGTHEN OVER OUR AREA
WED NIGHT AND THURSDAY AHEAD OF THE FRONT. ASSUMING AN MCS DOES
NOT BRING A CLOUD SHIELD OR COLD POOL OVER THE AREA DURING THE
MORNING, THE MOISTURE ADVECTION SHOULD AGAIN MAKE THERMODYNAMIC
PROFILES FAVORABLE FOR DEEP DIURNAL CONVECTION. THE VORT LOBE
AND FRONT WOULD APPEAR TIMED TO PROMOTE CONVECTIVE INITIATION IN
THE MOUNTAINS, AND PERHAPS THURSDAY EVENING IN THE PIEDMONT; CAM
RESPONSE IS GREATER TO OUR EAST AND SOUTHEAST. THE SHEAR AFFORDED
BY THE FAST 500MB FLOW AND FORCING ALONG THE FRONT COULD RESULT
IN AT LEAST LOOSELY ORGANIZED CONVECTIVE CLUSTERS AT THAT TIME
AND PERHAPS AT LEAST AN ISOLATED THREAT OF DAMAGING WIND. TEMPS
AND HUMIDITY INCREASE THURSDAY AND A FEW LOCATIONS IN THE LOWER
PIEDMONT COULD SEE HEAT INDEX RISE INTO THE LOWER 100S, AND A FEW
SPOTS MAY REACH HEAT ADVISORY CRITERIA.
THE FRONT ESSENTIALLY STALLS OVER THE AREA FRIDAY SEEMINGLY
AS A WAVE DEVELOPS ALONG IT, DUE TO INTERACTION WITH THE TROUGH
ALOFT. MOISTURE POOLING AND CONVERGENCE IN THE VICINITY OF THE FRONT
RESULT IN AN UPTICK IN PRECIP CHANCES FOR THE AREA, WITH SHEAR
STILL SUPPORTIVE OF LOOSELY ORGANIZED STORMS PRODUCING A NONZERO
SEVERE THREAT. CLOUD COVER IS EXPECTED TO BRING TEMPERATURES
DOWN A FEW DEGREES THOUGH DEWPOINTS WILL REMAIN HIGH. THE FRONT
GRADUALLY DRIFTS EAST FRIDAY NIGHT INTO SATURDAY, SO POPS TREND
LOWER AND SHIFT TOWARD THE COAST, WITH TEMPS ALSO TRENDING A
BIT COOLER. DRIER CONTINENTAL AIR WILL ARRIVE BEHIND THE FRONT;
THE MOUNTAINS MAY SEE A DIP IN DEWPOINTS AS SOON AS SATURDAY
AFTERNOON WHILE THE REMAINDER OF THE AREA SEES THE DRYING TREND
BEGIN SATURDAY NIGHT AND PARTICULARLY SUNDAY. TEMPS MAY ACTUALLY
REBOUND A BIT SUNDAY AND MONDAY OWING TO CLEARER SKIES, BUT THE
DRIER AIR SUGGESTS SUPPRESSED DIURNAL CONVECTION THOSE DAYS AND
POPS THUS MOSTLY REMAINING BELOW SLIGHT-CHANCE.
AVIATION /18Z TUESDAY THROUGH SUNDAY/
AT KCLT AND ELSEWHERE: ABUNDANT LOW VFR CUMULUS THIS AFTERNOON WITH
LIGHT NW WINDS. CUMULUS SHOULD DISSIPATE BY SUNSET LEAVING MOSTLY
SKC THOUGH FEW CIRRUS OCCASIONALLY MAY BE SEEN OVERNIGHT. WINDS
REMAIN LIGHT BUT VEER TO NE AT ALL SITES EXCEPT KAVL. WITH EXPECTED
GOOD RADIATIONAL COOLING, VALLEY FOG APPEARS LIKELY ENOUGH TO
INCLUDE TEMPO IFR AT KAVL IN THE MORNING. LESS COVERAGE OF CUMULUS
EXPECTED WED, WITH BASES ALSO MORE LIKELY TO REMAIN AT/ABOVE FL045
AT KCLT.
OUTLOOK: SCATTERED AFTERNOON/EVENING CONVECTION THURSDAY THROUGH
SATURDAY. LOW STRATUS AND FOG WILL BE POSSIBLE EACH MORNING,
ESPECIALLY IN THE MOUNTAIN VALLEYS.
GSP WATCHES/WARNINGS/ADVISORIES
GA...NONE.
NC...NONE.
SC...NONE.
JCW
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