371
FXUS62 KGSP 271054
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
654 AM EDT MON JUL 27 2026
WHAT HAS CHANGED
REMOVED DETAILS ABOUT MCS ACTIVITY THIS MORNING AS THE MAIN
THREAT HAS PASSED. NO MAJOR CHANGES TO THINKING FOR TUE. UPDATED
DISCUSSION FOR 12Z TAF ISSUANCE.
KEY MESSAGES
1. SEVERE WEATHER REMAINS POSSIBLE TUESDAY INTO EARLY WEDNESDAY
WITH THUNDERSTORMS DEVELOPING AHEAD OF A COLD FRONT.
2. A WARMING TREND IS EXPECTED THROUGH TUESDAY, WITH SLIGHTLY
COOLER HIGHS AND LOWER HUMIDITY RETURNING BY WEDNESDAY BEHIND
THE FRONT.
DISCUSSION
KEY MESSAGE 1: SEVERE WEATHER REMAINS POSSIBLE TUESDAY INTO EARLY
WEDNESDAY WITH THUNDERSTORMS DEVELOPING AHEAD OF A COLD FRONT.
THE "RING OF FIRE" PATTERN REMAINS IN PLACE TO START THE WEEK,
FEATURING A DEEP ANTICYCLONE OVER THE ROCKIES/PLAINS AND A
TROUGH OVER THE GREAT LAKES AND EAST COAST. CIRRUS DEBRIS WILL
BE SEEN OVER MUCH OF THE CWA THIS MORNING FROM DECAYING MCSS
FARTHER WEST, BUT THAT SHOULD THIN OR ADVECT OUT PRIOR TO PEAK
HEATING TODAY, SO PROBABLY WON'T BE A LIMITING FACTOR IN DIURNAL
CONVECTION. HOWEVER, THERMO PROFILES ARE QUITE DRY ABOVE THE PBL
AND WEAK CAPPING IS EXPECTED. THE REMNANT VORTEX GENERATED BY
THE MORNING MCSS PROBABLY WILL MISS US TO THE SOUTHWEST AS WELL,
SO WE WILL LACK MUCH ENHANCEMENT TO FORCING ASIDE FROM RIDGETOP
CONVERGENCE. THOUGH WITH THE PROFILES BEING DRY THERE MAY NOT BE
MUCH POSSIBILITY OF CONVECTIVE INITIATION EVEN IF AN MCV WERE TO
TRACK OVER OUR AREA. CAMS CONTINUE TO BE LARGELY DEVOID OF ANY
CELLS THIS AFTERNOON SO POPS REMAIN VERY LOW.
EXTREME INSTABILITY APPEARS LIKELY TO FORM THIS AFTERNOON IN THE
CENTRAL MISSISSIPPI VALLEY; WITH THE SYNOPTIC PATTERN REMAINING
VERY SIMILAR TO YESTERDAY, ANOTHER MCS LOOKS LIKELY TO DEVELOP
BY THIS AFTERNOON OR EVENING, WITH NW'LY CLOUD LAYER FLOW AND
FORWARD-PROPAGATING CORFIDI VECTORS SUGGESTING ONE COULD TRACK
ALONG THE WARM FRONTAL ZONE IN THE OH VALLEY, AND MAKE A RUN AT
THE NC MOUNTAINS AGAIN TONIGHT. THE 00Z NAM, 00Z RRFS, AND 18Z SUN
REFS ALL FEATURED A DECAYING MCS OR COLD POOL REACHING THE TN/NC
BORDER EARLY TUESDAY MORNING. GIVEN THE TIMING AND LIMITED MUCAPE,
THAT DOESN'T LOOK PARTICULARLY LIKELY TO PRODUCE SEVERE OR HYDRO
THREATS. THE 00Z HRRR APPEARS TO DEVELOP LOOSELY ORGANIZED STORMS
ALONG THE EAST FLANK OF THE COLD POOL WHICH ALSO REACHES THE NC
BORDER NEAR DAYBREAK TUESDAY. THIS RESULTS IN SOME POPS IN THAT
AREA AROUND THAT TIME; GIVEN THE DEGREE OF SHEAR CAN'T RULE OUT
SOME COLD POOL DRIVEN STRONG TO SEVERE GUSTS EVEN IF STORMS ARE NOT
PARTICULARLY TALL. SPC DAY 1 FEATURES A MARGINAL RISK IN THAT AREA,
POSSIBLY JUST CARRIED OVER FROM THE OLD DAY 2, BUT ALSO HANDLING
THE OUTSIDE CHANCE OF SUCH DEVELOPMENT BEFORE 8 AM EDT TUE.
THE POSSIBILITY OF THE MORNING COLD POOL OR MCS ARRIVAL CONTINUES
TO BE A SOURCE OF UNCERTAINTY IN ASSESSING OUR SEVERE POTENTIAL
TUESDAY, POTENTIALLY DELAYING WARMING AND KEEPING INSTABILITY IN
CHECK. ASSUMING THE COLD POOL IS NOT A FACTOR, TUESDAY SHOULD BE
A WARMER AND MORE UNSTABLE DAY. BY TUESDAY AFTERNOON A COLD FRONT
SHOULD REACH THE OHIO VALLEY AND THUS THE ENVIRONMENT UPSTREAM
MAY BE TOO STABLE TO SUPPORT AN MCS; THE MOST LIKELY AREA OF
DEVELOPMENT SHIFTS SOUTH INTO TN INSTEAD, AND AN MCS FORMING THERE
COULD PASS BY TO THE SOUTHWEST. DIFFERENTIAL HEATING ALONG A COLD
POOL OR CIRRUS DECK HOWEVER COULD INITIATE STORMS, IN ADDITION TO
THE TYPICAL RIDGETOP CONVERGENCE. THE SOUTHWARD PUSH OF THE COLD
FRONT LOOKS TO OCCUR LATE IN THE DAY OR IN THE EVENING, ORIENTED
EAST-WEST ACROSS OUR AREA. THE PEAK STORM THREAT MAY BE A BIT AFTER
PEAK HEATING OR EVEN AFTER SUNSET. 0-6KM SHEAR LOOKS LIKELY TO
BE 30-40 KT, SO SUPERCELL STRUCTURES ARE NOT OUT OF THE QUESTION,
THOUGH SHEAR VECTORS WOULD APPEAR TO BE SOMEWHAT PARALLEL TO THE
FRONT AND WE COULD SEE CELLS GROW UPSCALE INTO A QLCS. DAMAGING
WIND REMAINS THE MAIN THREAT THOUGH 1"-2" HAIL APPEARS POSSIBLE
WITH SUPERCELLS. ALL THIS SAID, DUE IN PART TO THE UNCERTAINTY
POSED BY A MORNING COLD POOL, POPS PEAK AT ONLY 20-40% OVER MOST
OF THE AREA SOUTH OF I-40, BUT SLIGHTLY HIGHER SOUTH AND EAST OF
CHARLOTTE SINCE THAT AREA SHOULD HAVE THE MOST TIME TO DESTABILIZE
AHEAD OF THE FRONT. NORTHWEST FLOW INTO THE MOUNTAINS COULD LEAD TO
ANOTHER ROUND OF ACTIVITY DEVELOPING TUE NIGHT OR EARLY WED NEAR
THE TN BORDER, BUT OTHERWISE THE CONVECTION SHOULD PUSH SOUTH AND
EAST BY LATE EVENING.
KEY MESSAGE 2: A WARMING TREND IS EXPECTED THROUGH TUESDAY, WITH
SLIGHTLY COOLER HIGHS AND LOWER HUMIDITY RETURNING BY WEDNESDAY
BEHIND THE FRONT.
SOUTHWEST FLOW AHEAD OF THE APPROACHING FRONT TUESDAY SHOULD
MAINTAIN VERY HUMID CONDITIONS AND WITH WAA, TEMPS ARE EXPECTED TO
TREND WARMER, INTO THE LOWER-MID 90S ACROSS THE PIEDMONT AND NEAR
90 IN THE MOUNTAIN VALLEYS. HEAT INDEX LIKELY WILL RISE TO 102-105
(LOCALLY HIGHER) IN MUCH OF THE PIEDMONT, WHILE THE VALLEYS SHOULD
REACH THE MID-90S. THERE REMAINS UNCERTAINTY DUE TO THE COLD POOL
OR CIRRUS FROM A POSSIBLE EARLY MORNING MCS ARRIVAL, THAT COULD
WRECK THE WARMING NECESSARY TO REACH THESE TEMPERATURES. CAREFUL
EVALUATION OF SUBSEQUENT CAM RUNS WILL BE NEEDED BEFORE MAKING
ANY DECISION ABOUT A POSSIBLE HEAT ADVISORY.
BEHIND THE FRONT, TEMPERATURES TREND BACK TO AROUND CLIMO ON
WEDNESDAY, WITH LOWER HUMIDITY THAT SHOULD KEEP INDICES BELOW 100,
AND MUCH MORE STABLE CONDITIONS SUCH THAT PRECIP CHANCES REMAIN
SMALL. APPRECIABLY DRIER AIR FILTERS IN FOR THURSDAY THAT BRINGS
POPS AND HEAT INDICES EVEN LOWER DESPITE TEMPS BEING ABOUT THE
SAME. THE UPSTATE AND NE GA, BEING WARMER, ACTUALLY SEE RH FALL
TO AROUND 35% THURSDAY AND FRIDAY, EXCEPTIONALLY LOW FOR THIS TIME
OF YEAR.
THE WESTERN RIDGE / EASTERN TROUGH PATTERN LINGERS INTO NEXT
WEEKEND, THOUGH NOT UNSTABLE UPSTREAM SO WE DO NOT EXPECT MCS
THREATS. THE NEXT CHANCES FOR RAIN/STORMS APPEAR TO BE SATURDAY,
WHEN A REINFORCING SHORTWAVE OR UPPER LOW ROTATES INTO THE EASTERN
TROUGH, AND INDUCES RETURN FLOW OVER THE OLD FRONT BY THEN STALLED
NORTH OF THE GULF COAST. POPS DEVELOP SATURDAY AND LINGER TO SUNDAY,
WITH TEMPS FALLING A BIT BELOW NORMAL DUE TO INCREASED CLOUD COVER.
AVIATION /12Z MONDAY THROUGH FRIDAY/
AT KCLT AND ELSEWHERE: CIRRUS DEBRIS FROM UPSTREAM CONVECTION WILL
LINGER EARLY THIS MORNING OVER THE SC SITES AND KAVL, WHICH SHOULD
INHIBIT DAYBREAK FOG FORMATION THERE. KCLT AND KHKY WILL BE CLEARER
AND THINK THERE STILL COULD BE A BRIEF FOG/STRATUS EVENT AT OR JUST
AFTER DAYBREAK. NOT EXPECTING MUCH SHRA/TSRA DEVELOPMENT TODAY,
ONLY DIURNAL CU FORMING NEAR MVFR/VFR THRESHOLD BEFORE MIXING UP TO
040-060 BY AFTERNOON. CAN'T RULE OUT RADIATION FOG/STRATUS TONIGHT
THOUGH NO MENTION YET MADE, DUE TO MINIMAL PRECIP COVERAGE EXPECTED
TODAY AND ALSO WITH LOW CONFIDENCE AS TO WHETHER ANY CIRRUS DEBRIS
WILL ADVECT ACROSS THE APPALACHIANS INTO THE TERMINAL AREA. LIGHT
WINDS, WITH SOME VARIABILITY DUE TO WEAK FORCING AND ALSO DUE TO
LEE TROUGH EXPECTED TO FORM THIS AFTN. BREEZY AND OCCASIONALLY
GUSTY TUE MORNING AT KCLT ONCE MIXING BEGINS.
OUTLOOK: STRONG TO SEVERE TSRA POSSIBLE TUES AFTERNOON/EVENING
AHEAD OF A COLD FRONT, BUT THAT DEVELOPMENT COULD BE LIMITED BY
DEBRIS CLOUDS OR STORM OUTFLOW FROM THE MORNING, SO CONFIDENCE
REMAINS LOW. QUIETER AND LESS HUMID WEATHER WED-FRI. 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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