343
FXUS62 KGSP 261055
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
655 AM EDT SUN JUL 26 2026
WHAT HAS CHANGED
UPDATED THE AVIATION DISCUSSION FOR THE 12Z TAF ISSUANCE AND
CLARIFIED SOME DETAILS ABOUT THE LIGHT SHOWERS ONGOING OVER THE
AREA.
KEY MESSAGES
1. THE SEVERE THREAT REMAINS LOW THROUGH MONDAY BEFORE INCREASING
MONDAY NIGHT INTO TUESDAY, AHEAD OF A COLD FRONT. SOME STORMS
COULD LINGER INTO EARLY WEDNESDAY. A WARMING TREND IS EXPECTED
THROUGH TUESDAY, WITH SLIGHTLY COOLER HIGHS AND LOWER HUMIDITY
WEDNESDAY INTO NEXT WEEKEND.
DISCUSSION
KEY MESSAGE 1: THE SEVERE THREAT REMAINS LOW THROUGH MONDAY BEFORE
INCREASING MONDAY NIGHT INTO TUESDAY, AHEAD OF A COLD FRONT. SOME
STORMS COULD LINGER INTO EARLY WEDNESDAY. A WARMING TREND IS
EXPECTED THROUGH TUESDAY, WITH SLIGHTLY COOLER HIGHS AND LOWER
HUMIDITY WEDNESDAY INTO NEXT WEEKEND.
SURFACE FRONT LOOKS TO BE ORIENTED NW-SE ACROSS THE CWA EARLY THIS
MORNING, EXTENDING UPSTREAM INTO THE LOWER OHIO VALLEY. ALOFT,
A FULL-LATITUDE TROUGH IS IN PLACE OVER THE EASTERN SEABOARD AND
GREAT LAKES, WITH A DEEP, BROAD UPPER ANTICYCLONE SITUATED OVER
THE ROCKIES/PLAINS. THIS PATTERN WILL LEAVE US IN A PERSISTENT NW
FLOW REGIME ALOFT THROUGH THE FIRST HALF OF THE WEEK, AND MULTIPLE
SUBTLE EMBEDDED SHORTWAVES OR RIPPLES OF VORTICITY ARE EXPECTED TO
DIVE THROUGH THE TROUGH AND OVER THE SOUTHERN APPALACHIAN REGION,
POTENTIALLY ENHANCING THE DEVELOPMENT OF CONVECTIVE COMPLEXES,
SOME OF WHICH MAY BE NONDIURNAL IN NATURE.
TODAY AND MONDAY, FORCING IS RATHER ILL-DEFINED OVERALL. SOME
SHOWER ACTIVITY IS ONGOING AS OF 7 AM WITH ONE OF THE EMBEDDED
SHORTWAVES AND THE LLJ ACTING TOGETHER. DRIER AIR WILL GRADUALLY
FILTER INTO THE AREA LATER THIS MORNING AND SHOULD PUSH THE FRONTAL
MOISTURE SOUTHWARD; THE MORNING SHOWERS SHOULD DIMINISH IN PART
DUE TO THE DIURNAL WEAKENING OF THE LLJ. RIDGETOP CONVERGENCE,
AND/OR A LEE TROUGH AT THE SURFACE, POTENTIALLY WILL FIRE A FEW
STORMS THIS AFTERNOON EVEN IF THE SHORTWAVES ALOFT AREN'T A FACTOR,
SO WE RETAIN 20-40% POPS OVER MUCH OF THE AREA DOWNSTREAM OF THE
BLUE RIDGE ESCARPMENT. 0-6KM SHEAR WILL BE HIGH FOR THIS TIME OF
YEAR, 30-40 KT, WITH 0-3KM SHEAR 15-25 KT. THOUGH INSTABILITY WILL
BE LIMITED BY WEAK LAPSE RATES, ANY STORMS THAT DO FIRE MAY FORM
INTO CLUSTERS, AND IF THAT WERE TO OCCUR THEY COULD POSE A RISK
OF DAMAGING WIND. THE 00Z NAM DEVELOPS CONVECTION OVER THE AREA
AFTER SUNSET WHICH COULD BE PARTIALLY DUE TO ONE OF THE EMBEDDED
RIPPLES ALOFT, BUT CONFIDENCE IS LOW ON WHERE THAT MIGHT HAPPEN IF
AT ALL. THE CONTINUED DRYING LEAVES BEHIND DRY AND SLIGHTLY CAPPED
PROFILES IN PLACE FOR MONDAY, WHICH RESULTS IN ONLY 10-20% POPS
AT BEST. SHEAR PARAMETERS WILL BE SIMILAR BUT THE SEVERE THREAT
DURING THE AFTERNOON WOULD APPEAR TO BE LOWER ON ACCOUNT OF LOWER
INSTABILITY. A FEW MODELS HAVE BEEN HINTING AT A POSSIBLE MCV OR
COLD POOL ARRIVING MONDAY NIGHT FROM AN UPSTREAM MCS, BUT EVEN
IF THAT WERE TO OCCUR IT WOULD APPEAR UNLIKELY TO SURVIVE OVER
THE APPALACHIANS WITH THE UNFAVORABLE THERMODYNAMIC PROFILES. SPC
DOES HINT AT THE POSSIBILITY OF AN MCS REACHING THE FAR NORTHERN
OR WESTERN PORTIONS OF THE CWA BEFORE FALLING APART, BY INCLUDING
THOSE AREAS IN A MARGINAL RISK ON DAY 2. CURRENTLY CAN'T ADVOCATE
FOR ANY MORE OF THE CWA BEING INCLUDED THAN THOSE AREAS.
A BETTER DEFINED SHORTWAVE WILL ROTATE INTO THE TROUGH ON TUESDAY
AND WILL BRING A COLD FRONT SOUTHWARD TOWARD OUR AREA. ASSUMING WE
ARE NOT STILL STABILIZED BY A COLD POOL OR DEBRIS CLOUDINESS FROM
MONDAY NIGHT, OUR MCS POTENTIAL STILL LOOKS GREATEST LATE TUESDAY
INTO TUESDAY NIGHT: WAA AHEAD OF THE FRONT SHOULD PROMOTE WARMER
DAYTIME TEMPS AND DEEPER MIXING WHICH SHOULD OVERCOME THE CAP,
SO WE WILL SEE INSTABILITY RETURN TO VALUES MORE TYPICAL OF A
HOT JULY AFTERNOON, STILL WITH FAVORABLE SHEAR AND SFC-MIDLEVEL
DELTA-THETA-E VALUES SUGGESTING EASY COLD POOL FORMATION AHEAD
OF THE FRONT. HODOGRAPHS HAVE ENOUGH CURVATURE TO EXPECT A FEW
SUPERCELLS COULD FORM EVEN IF THE MCS WERE NOT TO PAN OUT. TIMING OF
THE FRONT SUGGESTS CONVECTIVE/SEVERE THREAT COULD BE GREATEST AFTER
PEAK HEATING, WELL INTO TUESDAY NIGHT PARTICULARLY IN THE SOUTHERN
CWA. CONFIDENCE IS STILL LIMITED PARTLY DUE TO NOT KNOWING HOW
ANY COLD POOL FROM MONDAY NIGHT COME INTO PLAY. DAY 3 OUTLOOK NOW
FEATURES SLIGHT RISK FOR THE NORTHERN TWO-THIRDS OR SO OF THE AREA,
WITH MARGINAL FOR THE REMAINDER. TEMPS TUESDAY WILL BE THE WARMEST
OF THE WEEK, MOSTLY IN THE LOWER TO MID 90S ACROSS THE PIEDMONT;
HEAT INDEX IS LIKELY TO EXCEED 100 AND MAY REACH 105 IN THE URBAN
AREAS IN THE I-85 CORRIDOR OR SOUTHEAST.
TEMPS TREND BACK TO NEAR OR SLIGHTLY BELOW NORMAL WED-SAT IN THE
WAKE OF THE FRONT, BUT PERHAPS OF MORE INTEREST HUMIDITY SHOULD
BE MUCH LOWER WITH DEWPOINTS FALLING INTO THE LOWER 60S EACH
AFTERNOON. THE RIDGE-TROUGH PATTERN ACROSS THE CONUS DOES NOT
BREAK DOWN, HOWEVER. THE FRONT WILL STALL NORTH OF THE GULF COAST
AND POTENTIALLY WILL BE REACTIVATED BY THE NEXT SHORTWAVE OR LOW
DIVING PAST THE ANTICYCLONE. A FEW DIURNAL SHOWERS/STORMS APPEAR
POSSIBLE BY FRIDAY WITH CHANCE POPS FOR ALL AREAS ON SATURDAY WITH
THE ACTIVATING FRONT.
AVIATION /12Z SUNDAY THROUGH THURSDAY/
AT KCLT AND ELSEWHERE: WIDESPREAD CIGS ACROSS THE TERMINAL AREA
AT DAYBREAK, MOSTLY AT IFR, NEAR STALLED FRONTAL BOUNDARY. A WEAK
DISTURBANCE HIGHER ALOFT, COUPLED WITH NORTHWEST FLOW INTO THE
APPALACHIANS, HAS PRODUCED AN AREA OF SHRA WITHIN THE CLOUD DECK,
WITH A COUPLE EMBEDDED TSRA. SOME AREAS WHICH SAW BRIEF CLEARING
IN THE PREDAWN HOURS DEVELOPED APPARENT RADIATION FOG/STRATUS;
WITH THAT AND THE SHRA/TSRA MIXING OUT CLOUDS WE HAVE A TRICKY
MORNING FORECAST WITH RAPID CATEGORY CHANGES LIKELY. ALL SITES
EXCEPT KAND START OFF WITH A TEMPO FOR CATEGORY VARIATIONS. SOME
SLIGHT IMPROVEMENT SHOULD OCCUR OVER THE MORNING AS THE PRECIP
DIMINISHES OR ADVECTS OUT AND AS DOWNSLOPE FLOW PAST THE MOUNTAINS
PROMOTES DRYING/MIXING. ASIDE FROM KAVL WHICH SHOULD STAY NW,
WINDS ARE ALSO GOING TO BE TRICKY WITH VERY WEAK SFC FLOW, MIXING
INTO THE NW WINDS ALOFT, BUT ALSO EXPECTED FORMATION OF LEE TROUGH
THIS AFTN. A FEW DIURNAL SHRA/TSRA ARE POSSIBLE AT THE UPSTATE
SITES AND KHKY TODAY, WHICH COULD BE GUSTY; LOWER CHANCE AT KCLT
IS HANDLED WITH ONLY VCSH. SOME RADIATION FOG/STRATUS IS LIKELY
TO DEVELOP AGAIN TONIGHT BUT WITH LOW CONFIDENCE NOT YET INCLUDING
ANY RESTRICTIONS FOR MON AM EXCEPT FOR KAVL, DUE TO VALLEY LOCATION.
OUTLOOK: ONLY ISOLATED TSRA EXPECTED MONDAY
AFTERNOON/EVENING. STRONG TO SEVERE THUNDERSTORMS, AS WELL AS BREEZY
SW WINDS ARE POSSIBLE TUESDAY AFTERNOON/EVENING AHEAD OF A COLD
FRONT. THE SEVERE STORM THREAT COULD LINGER INTO EARLY WEDNESDAY,
BUT CONFIDENCE IS LOW AT THIS TIME. LOW STRATUS AND/OR FOG WILL
BE POSSIBLE EACH MORNING, MAINLY IN THE MTN VALLEYS.
GSP WATCHES/WARNINGS/ADVISORIES
GA...NONE.
NC...NONE.
SC...NONE.
JCW
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