303
FXUS62 KGSP 011828
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
228 PM EDT SAT AUG 1 2026
WHAT HAS CHANGED
NO SIGNIFICANT CHANGES TO THE PUBLIC FORECAST THIS AFTERNOON.
THE AVIATION FORECAST WAS UPDATED TO REFLECT THE RECENT 18Z TAF
ISSUANCE.
KEY MESSAGES
1. A STALLED FRONTAL BOUNDARY TO OUR WEST PRODUCES MULTIPLE
ROUNDS OF SHOWERS AND THUNDERSTORMS CAPABLE OF PRODUCING HEAVY
DOWNPOURS AND ISOLATED FLASH FLOODING. A LOW-END SEVERE WEATHER
RISK IS ALSO IN STORE FOR SUNDAY.
2. TYPICAL SUMMERTIME WEATHER RETURNS NEXT WEEK, WITH HOT AND
MUGGY CONDITIONS AND AFTERNOON SHOWERS AND THUNDERSTORMS.
DISCUSSION
KEY MESSAGE 1: A STALLED FRONTAL BOUNDARY TO OUR WEST PRODUCES
MULTIPLE ROUNDS OF SHOWERS AND THUNDERSTORMS CAPABLE OF PRODUCING
HEAVY DOWNPOURS AND ISOLATED FLASH FLOODING. A LOW-END SEVERE
WEATHER RISK IS ALSO IN STORE FOR SUNDAY.
WATER VAPOR IMAGERY AS WELL AS THIS MORNING'S 12Z RAOB ANALYSIS
DEPICT A 574DM UPPER LOW LOCATED OVER CENTRAL ILLINOIS, ATOP A
MORE OR LESS VERTICALLY-STACKED LOW PRESSURE SYSTEM EVIDENT ON
SURFACE MAPS. A BROAD BLOCKING RIDGE IS LOCATED OVER THE WESTERN
ATLANTIC. AND THOUGH SUBTLE, THERE WOULD APPEAR TO BE A WEAK
BOUNDARY LOCATED ALONG I-85, AT THE NORTHERN TERMINUS OF A DEEP
MOISTURE PLUME ADVECTED INTO THE AREA OVERNIGHT. WIDESPREAD CLOUD
COVER HAS ONLY VERY RECENTLY BEGUN TO CLEAR OUT EFFECTIVELY, AND
RECENT RUNS OF THE HRRR HAVE RESPONDED BY BACKING OFF ON COVERAGE
OF SHOWERS AND THUNDERSTORMS FOR THIS AFTERNOON. STILL...ALREADY
SEEING SOME SHOWERS BREAK OUT ACROSS THE EXTREME SOUTHERN AND
EASTERN PORTIONS OF THE UPSTATE...AND WOULDN'T BE SURPRISED IF
SOME OF THIS ACTIVITY CONTINUES TO STRENGTHEN OVER THE COMING HOURS.
THE UPPER LOW WILL ONLY SLOWLY MAKE TRACKS EASTWARD OVER THE
NEXT 48 HOURS, DETERRED BY THE BLOCKING RIDGE OVER THE ATLANTIC.
AS A RESULT, THERE'LL BE LIMITED FORCING FOR ASCENT THROUGH
THIS EVENING, AND IT'LL BE DIFFICULT TO EFFECTIVELY TRIGGER MUCH
CONVECTION. WHATEVER CELLS SUCCESSFULLY DEVELOP WILL ENCOUNTER
AN ENVIRONMENT LARGELY INHOSPITABLE FOR SEVERE WEATHER: ONLY SOME
1000-1500 J/KG SBCAPE IS FORECAST ACROSS THE NORTHERN 2/3S OF THE
CWA (PERHAPS LESS, SHOULD LINGERING CLOUD COVER HINDER DAYTIME
HEATING MUCH LONGER), SHEAR WILL BE QUITE LIMITED, AND DCAPE
VIRTUALLY NONEXISTENT. MID-LEVEL LAPSE RATES WILL BE PRACTICALLY
MOIST ADIABATIC, RESULTING IN MOSTLY WEAK UPDRAFTS WITH ONLY
LIMITED BUOYANCY. RATHER, THE BIGGER THREAT WOULD APPEAR TO BE
HEAVY RAINFALL, WITH PWS AS HIGH AS 1.9-2.1" THROUGH TONIGHT AS
A 20-30KT LLJ ADVECTS MORE AND MORE MOISTURE INTO THE REGION.
THIS IS NEAR THE HIGH END OF CLIMATOLOGY, AND MORE THAN ENOUGH
FOR EFFICIENT RAINFALL PRODUCTION BY ANY BETTER STORM DEVELOPING
IN THIS ENVIRONMENT.
SOME OF THE HI-RES GUIDANCE STILL HINTS AT A ROUND OF SHOWERS
REDEVELOPING IN THE PREDAWN HOURS SUNDAY. BY FAR THE BIGGER STORY,
HOWEVER, WILL BE THE AFTERNOON SUNDAY. BY THIS POINT IN TIME,
THE UPPER TROUGH (OR LOW, DEPENDING ON YOUR CHOICE OF MODEL) SHOULD
HAVE DRAWN CLOSE ENOUGH THAT MORE APPRECIABLE SYNOPTIC FORCING AS
WELL AS STRONG UPPER FLOW IN GENERAL WILL COVER THE AREA. AS A
RESULT, MUCH BETTER DEEP-LAYER SHEAR, ON THE ORDER OF 20-30KTS,
SHOULD BE IN PLACE OVER MUCH OF THE AREA. AS MUCH AS 2500 J/KG
SBCAPE CAN BE EXPECTED ACROSS MUCH OF THE AREA. THE HI-RES
GUIDANCE DOESN'T QUITE HAVE A HANDLE ON THE EVOLUTION OF SUNDAY'S
CONVECTION...BUT PATTERN RECOGNITION ALONE SAYS WE CAN EXPECT MORE
WIDESPREAD ACTIVITY AND SOME DEGREE OF ORGANIZATION LENDING ITSELF
TO A LOW-END DAMAGING WIND THREAT. STILL, AS MOIST AS PROFILES
ARE, THINK ANY ACTUAL SEVERE WILL BE ISOLATED, AND THE GREATER
POTENTIAL WILL ONCE AGAIN BE FOR TRAINING CELLS ACROSS THE AREA,
AND RESULTANT ISOLATED FLASH FLOODING.
KEY MESSAGE 2: TYPICAL SUMMERTIME WEATHER RETURNS NEXT WEEK, WITH HOT
AND MUGGY CONDITIONS AND AFTERNOON SHOWERS AND THUNDERSTORMS.
LONG-RANGE ENSEMBLES CONTINUE TO FEATURE EITHER A CLOSED UPPER LOW
OR A WEAKENING UPPER TROUGH SANDWICHED BETWEEN RIDGES OVER THE
WESTERN ATLANTIC AND CENTRAL CONUS, RESULTING IN SOME LEVEL OF
MOISTURE RETURN PERSISTING THROUGH THE WEEK. WITHOUT ANY CLARITY ON
THE SYNOPTIC PATTERN, IT'S TOUGH TO SAY WHAT THIS WILL MEAN FOR THE
CONVECTIVE FORECAST; RIGHT NOW IT WOULD LOOK LIKE A RETURN TO
DIURNAL SHOWERS AND STORMS IS LIKELY, BUT IF A TRUE CLOSED LOW
PERSISTS FOR DAYS, WE COULD BE UNDER THE GUN FOR MORE WIDESPREAD
COVERAGE THAN NORMAL BY DAY, AND SOME PERSISTENCE OF POPS INTO THE
OVERNIGHT.
AVIATION /18Z SATURDAY THROUGH THURSDAY/
AT KCLT AND ELSEWHERE: AS A PLUME OF MOISTURE CONTINUES TO ADVECT
INTO THE WESTERN CAROLINAS, LOWERED CEILINGS HAVE BEEN VERY SLOW TO
IMPROVE, WITH IFR STILL REPORTED AT A NUMBER OF TERMINALS UP UNTIL
AN HOUR AGO, AND STILL WIDESPREAD MVFR CEILINGS AT 1500-2500FT.
STILL THINK THERE'LL BE IMPROVEMENT TO VFR IN THE NEXT 1 TO 2 HOURS.
DESPITE THE LINGERING CLOUD COVER, SOME CONVECTION HAS ALREADY
BEGUN TO INITIATE SOUTH OF I-85, AND THIS ACTIVITY SHOULD BEGIN
TO EXPAND AS DAYTIME HEATING IMPROVES AND INSTABILITY INCREASES.
HI-RES GUIDANCE CONTINUES TO STRUGGLE WITH THE EVOLUTION OF
TODAY'S ACTIVITY...BUT GENERALLY STILL THINK THAT A ROUND IN THE
AFTERNOON WILL BE FOLLOWED BY A POSSIBLE SECOND ROUND OF RAINFALL
AROUND AND AFTER SUNSET. THEREAFTER, EVEN AS COVERAGE OF SHRA/TS
DECREASES OVERNIGHT, ANOTHER MURKY NIGHT SHOULD SET IN, WITH IFR
TO LIFR CEILINGS AND PATCHY FOG REDEVELOPING ACROSS THE TERMINAL
FORECAST AREA. IT'S UNCLEAR HOW CONVECTION WILL DEVELOP ON SUNDAY,
BUT THINK THAT AT LEAST SCATTERED COVERAGE IS LIKELY BASED ON
CURRENT GUIDANCE.
OUTLOOK: SHOWER AND THUNDERSTORM CHANCES, ALONG WITH ASSOCIATED
FLIGHT RESTRICTIONS, ARE EXPECTED TO LINGER THROUGH AT LEAST
THE MIDDLE OF NEXT WEEK. IN ADDITION TO THE USUAL DAYTIME
DIURNAL CONVECTION, SOME NIGHTS MAY FEATURE LINGERING SHOWERS AND
THUNDERSTORMS INTO THE FIRST PART OF THE OVERNIGHT. PATCHY FOG AND
LOW STRATUS WILL BE POSSIBLE IN THE MOUNTAIN VALLEYS EACH MORNING,
AND WHEREVER HEAVIER RAINFALL DEVELOPED THE PREVIOUS EVENING.
GSP WATCHES/WARNINGS/ADVISORIES
GA...NONE.
NC...NONE.
SC...NONE.
MPR
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