194
FXUS62 KGSP 081058
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
658 AM EDT THU MAY 8 2025
SYNOPSIS
STRONG TO SEVERE STORMS MAY BE CAPABLE OF PRODUCING DAMAGING WIND
GUSTS AND LARGE HAIL THIS AFTERNOON AND EVENING. A COLD FRONT
ARRIVES FRIDAY AND STALLS OVER THE SOUTHEAST THIS WEEKEND INTO
EARLY NEXT WEEK, KEEPING UNSETTLED WEATHER AROUND FOR DAYS. HIGHS
WILL REMAIN ABOVE NORMAL TROUGH FRIDAY BEFORE DROPPING WELL BELOW
NORMAL THIS WEEKEND INTO EARLY NEXT WEEK.
NEAR TERM /THROUGH TONIGHT/
AS OF 645 AM: WARM FRONT REMAINS IN SIMILAR POSITION TO WHERE IT
WAS WEDNESDAY, ALTHOUGH FLOW OVER IT HAS TURNED SOMEWHAT WESTERLY
AND SO ISENTROPIC LIFT SEEMS JUST BARELY ENOUGH TO KEEP LOW LEVEL
CLOUD OVER IN PLACE IN THE WESTERN ZONES GIVEN SPOTTY NATURE
OF LOW CLOUDS THERE. SHOWERS AND EVEN A FEW T-STORMS NOW IN THE
UPSTATE DEVELOPED WITH NOCTURNAL LLJ RIDING OVER THE FRONT; CAN'T
RULE OUT SOME MORE DEVELOPMENT VIA THAT MECHANISM BUT WITH THE LLJ
DIMINISHING, THAT IS UNLIKELY. A LULL IN PRECIP CHANCES IS EXPECTED
BETWEEN APPROX. 12-16Z TODAY IN THE WAKE OF THE SHORTWAVE AND WITH
THE FRONT CONTINUING TO OFFER ONLY WEAK FORCING. PARTLY CLOUDY
SKIES WILL HELP TEMPS RISE WELL ABOVE NORMAL TODAY, INTO THE LOWER
80S IN THE PIEDMONT AND THE FRENCH BROAD AND LITTLE TN VALLEYS.
HEIGHTS WILL BEGIN TO FALL OVER THE CWA BY LATE MORNING AS THE UPPER
LOW NOW OVER THE OZARKS GETS PICKED UP BY THE DIGGING LOW NEAR THE
EASTERN GREAT LAKES. LOW LEVEL WINDS REMAIN WEAK BUT THE APPROACH OF
THE COMBINED TROUGH APPEARS TO REACTIVATE THE WARM FRONT DURING THE
AFTERNOON. BY THAT TIME HOWEVER FAIRLY ROBUST DIURNAL INSTABILITY
LOOKS TO DEVELOP, WITH 1000-2000 J/KG OF SBCAPE; WE ARE FOR WANT
OF A SURFACE TRIGGER OTHER THAN RIDGETOP CONVERGENCE. IT IS NOT
TOO SURPRISING THAT CAMS PLUS THE NAM/GFS FIRE UP CELLS ON THE
EAST-FACING BLUE RIDGE ESCARPMENT IN THE MID TO LATE AFTERNOON,
A LITTLE LATER THAN PEAK HEATING. THIS ACTIVITY WILL BE EXPOSED TO
30-40 KT OF WESTERLY DEEP LAYER SHEAR SO SUPERCELLS OR ORGANIZED
MULTICELLS WOULD BE THE PREFERRED STORM MODE. SFC-MIDLEVEL THETA-E
LAPSES ARE 20-25 K ON THE NAM, WHICH IS TYPICAL FOR THIS TIME OF
YEAR AND INDICATIVE OF SOME DEGREE OF DOWNBURST/FFD SEVERE WIND
THREAT. THE SOMEWHAT UNUSUAL FINDING IS PERSISTENT STRONG 850-700MB
AND 700-500MB LAPSE RATES AT OR ABOVE 7 C/KM, WITH FREEZING LEVELS
ONLY AROUND 10 KFT, TOGETHER SUGGESTING A GREATER THAN USUAL HAIL
THREAT GIVEN THE SHEAR. SPC HAS HIGHLIGHTED THE MOUNTAINS IN A RARE
(FOR OUR NECK OF THE WOODS) HATCHED AREA SIGNALING THE POSSIBILITY
OF HAIL > 2" DIAMETER.
CAMS CONTINUE TO DEPICT UPSCALE GROWTH ALONG COLD POOLS WITH THE
INITIALLY DISCRETE ACTIVITY; THE SHEAR AND MEAN WIND SHOULD CARRY
THE AFTERNOON/EARLY EVENING CELLS MAINLY EAST INTO THE NC PIEDMONT,
ALTHOUGH WITH SW'LY NEAR-SFC FLOW AND THE WESTERLY SHEAR, SOME
INITIATION IS EXPECTED ALONG THE EDGE OF THE COLD POOL THROUGH
EVENING AND POTENTIAL FOR GROWTH INTO A LINEAR MODE. THERE IS
CONSENSUS FOR THE PEAK POPS AND SEVERE THREAT IN THE SC/GA ZONES
THIS EVENING, WITH CHANCES TAPERING OFF AROUND OR A LITTLE AFTER
MIDNIGHT. WHAT TORNADO THREAT THERE IS WOULD APPEAR TO INCREASE
IN THE EVENING AS LCLS LOWER AND AS LOW LEVEL HODOGRAPHS LENGTHEN
WITH DEVELOPING LLJ. THIS DOES LOOK LIKE THE LEAST OF THE THREE
THREATS BUT CAN'T BE RULED OUT.
THE TROUGH WILL BE ASSOCIATED WITH A COLD FRONT WHICH LOOKS TO
REMAIN WEST OF THE MOUNTAINS UNTIL THIS EVENING, PROGRESSING INTO
THE CWA OVERNIGHT. THE LAPSE RATES BEING STRONG INVOF THE DIGGING
TROUGH, WHEREVER CONVECTION DOES NOT OVERTURN THE ATMOSPHERE IN
OUR CWA, DECENT MUCAPE SIMILAR TO THE PEAK SBCAPE VALUES FROM
AFTERNOON MAY STILL BE PRESENT, SO NEW CONVECTION COULD BE SPAWNED
ALONG THE FRONT AS WELL. PARTLY FOR THIS REASON AT LEAST A LOW
CHANCE OR SLIGHT CHANCE POP LINGERS NEARLY UNTIL DAYBREAK IN OUR
MOUNTAINS. PATCHY FOG IS LIKELY TO DEVELOP TONIGHT WHERE PRECIP
OCCURS AFTER SUNSET ESPECIALLY IF CONVECTIVE DEBRIS ADVECTS OUT
BEFORE DAYBREAK; THIS IS MOST LIKELY IN THE MOUNTAINS/FOOTHILLS.
SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/
AS OF 246 AM EDT THURSDAY: BY FRIDAY, OPERATIONAL GUIDANCE DEPICTS
A HIGHLY AMPLIFIED Z500 TROUGH CENTERED OVER THE UPPER OHIO VALLEY
AND QUICKLY PIVOTING EAST...PERHAPS EVEN CUTTING OFF FROM THE MEAN
FLOW AS IT DOES SO. AT THE SURFACE, A WEAK COLD FRONT WILL JUST
BE ENTERING THE AREA FROM THE WEST...AND HI-RES GUIDANCE SUGGESTS
THAT A BAND OF SHOWERS AND EMBEDDED THUNDER WILL BE IN OR JUST EAST
OF THE I-77 CORRIDOR...FOLLOWING THE STRONGEST SYNOPTIC FORCING.
LOWS FRIDAY MORNING WILL SINK INTO THE UPPER 50S IN MOST LOCATIONS.
THE FRONT LOOKS LIKE IT'LL BE DIFFUSE ENOUGH THAT ONLY SLOW AIR MASS
MODIFICATION IS EXPECTED, SUCH THAT FRIDAY AFTERNOON MAY FEATURE
ANOTHER ROUND OF CONVECTION. SEVERE PROSPECTS STILL LOOK NOTABLY
LOWER THAN THURSDAY'S; HOWEVER, THE LATEST 00Z CYCLE OF GUIDANCE
COLLECTIVELY BRINGS THE TROUGH A FIT FARTHER SOUTH AND SLOWS IT
DOWN JUST A BIT...SO THAT AS INSTABILITY BEGINS RAMPING UP IN THE
EARLY AFTERNOON, THERE'LL STILL BE SOME LINGERING SHEAR...AND THUS
A BRIEF PERIOD OF ~1000 J/KG SBCAPE COLOCATED WITH ~30KTS OF DEEP
LAYER SHEAR. THIS IS ENOUGH TO SUPPORT AT LEAST LOOSELY-ORGANIZED
STORMS. THE LIMITING FACTOR WILL BE MOISTURE; LOWER SURFACE
DEWPOINTS AND GENERALLY DRIER PROFILES THROUGH THE COLUMN WILL
MAKE INITIATION MORE DIFFICULT...AND INDEED THE NAMNEST, FV3,
AND ARW, ALL OF WHICH NOW RUN OUT THROUGH FRIDAY EVENING, DEPICT
SOME ATTEMPT AT GETTING A RAGTAG LINE OF SHOWERS AND STORMS GOING
OVER THE PIEDMONT AND UPSTATE, BUT WITH MUCH LESS VIGOR AND LOWER
COVERAGE THAN THURSDAY'S SYSTEM.
ON FRIDAY NIGHT, HIGH PRESSURE WILL SETTLE INTO THE AREA MORE
DECIDEDLY, FURTHER DRYING THE LOW LEVELS. ALTHOUGH SOME LOW LEVEL
MOISTURE IS STILL PROGGED TO WORK INTO THE FORECAST AREA, ENSEMBLES
HAVE BACKED OFF ON THIS CONSIDERABLY, AND DRIER WEATHER IS ONCE
AGAIN THE FAVORED SOLUTION FOR SATURDAY INTO SATURDAY EVENING.
STILL, CAN'T RULE OUT AT LEAST SOME PATCHY STRATIFORM RAIN DURING
THE AFTERNOON, PARTICULARLY FOR THE SOUTHERN ZONES IN THE SC
UPSTATE...LESS SO FOR LOCATIONS NORTH OF THE NC-SC STATE LINE.
BY THE LATE EVENING, ENOUGH MOISTURE WILL BE WORKING INTO THE
REGION TO SUPPORT A STEADY INCREASE IN POPS GOING INTO THE EXTENDED.
LONG TERM /SUNDAY THROUGH WEDNESDAY/
AS OF 309 AM EDT THURSDAY: THE COMBINATION OF INCREASING RAINFALL
AND STRENGTHENING NE FLOW OWING TO HIGH PRESSURE ANCHORED OFF THE
NEW ENGLAND COAST WILL DRIVE THE DEVELOPMENT OF HYBRID COLD-AIR
DAMMING ON SUNDAY AND MONDAY. WIDESPREAD STRATIFORM RAIN IS
THEREFORE EXPECTED, AND BASED ON MODEL QPF RESPONSE, THE SIGNAL
FOR AT LEAST SOME LOW-END HYDRO ISSUES IS INCREASING. LONG-RANGE
ENSEMBLES CONTINUE TO DEPICT SOME EROSION ON MONDAY AFTERNOON AS
DAYTIME MIXING SCOURS OUT THE WEDGE...WHICH WOULD PERMIT SOME
THUNDERSTORM DEVELOPMENT OVER THE SOUTHERN AND EASTERN FRINGES
OF THE FORECAST AREA. BELOW NORMAL TEMPERATURES ARE EXPECTED
BOTH DAYS.
BY TUESDAY, THE SURFACE HIGH WILL BEGIN DRIFTING EAST, CUTTING OFF
SYNOPTIC SUPPORT FOR THE CAD, AND ALLOWING SLOW EROSION THROUGH THE
REMAINDER OF THE PERIOD. GUIDANCE SUGGESTS THAT WE'LL BE ABLE TO
MIX OUT MORE RELIABLY ON TUESDAY AFTERNOON, PERMITTING A RETURN TO
MORE SHOWERY AFTERNOON RAIN...AND HOPEFULLY SOME DRYING BY TUESDAY
EVENING. DETAILS FOR WEDNESDAY REMAIN QUITE UNCLEAR...WITH SOME
ENSEMBLE MEMBERS DEPICTING ANOTHER DAY OF AFTERNOON SHOWERS...AND
OTHER MEMBERS DEPICTING DRIER CONDITIONS.
AVIATION /12Z THURSDAY THROUGH MONDAY/
AT KCLT AND ELSEWHERE: A WEAK AND SOMEWHAT ILL-DEFINED FRONTAL ZONE
REMAINS OVER THE TERMINAL AREA AND IS RESPONSIBLE FOR LOW VFR TO
MVFR CIGS NEAR THE SC SITES AND KAVL. SOME SHRA/TSRA DEVELOPED
VIA SAME MECHANISM, AND ALTHOUGH THE MORNING THREAT HAS LIKELY
PASSED FOR THE SC SITES, CAN'T COMPLETELY RULE OUT NEW DEVELOPMENT
IN THAT AREA BEFORE 14Z. OTHERWISE, MAINLY MIDLEVEL CLOUDS AND
CIRRUS AROUND THE AREA UNTIL DIURNAL CU DEVELOP LATE MORNING TO
MIDDAY. UNSTABLE PROFILES THIS AFTN WITH LITTLE TO NO TRIGGER
DURING PEAK HEATING ASIDE FROM RIDGETOP CONVERGENCE. SHRA/TSRA
LOOK TO FIRE OVER THE MOUNTAINS A BIT LATER THAN THE TYPICAL
TIME NEAR AND NE OF KAVL, THEN PROPAGATE EAST AND SOUTH THRU THE
EVENING. HENCE PROB30 INCLUDED AT ALL SITES FOR TSRA, BEGINNING
AT 20Z AT KAVL AND PROGRESSIVELY LATER EAST AND SOUTH. STRONG WIND
GUSTS TO NEAR 30 KT, MAYBE HIGHER, WILL BE POSSIBLE WITH ANY TSRA
AND POSSIBLY DIME SIZE OR LARGER HAIL BIG ENOUGH TO CAUSE AT LEAST
MINOR DAMAGE (KAVL/KHKY AT GREATEST THREAT FOR > 1" HAIL). SHRA/TSRA
SHOULD PROPAGATE SOUTH OF THE TERMINALS BY 05-06Z. RESTRICTIONS
LIKELY TO DEVELOP IN THE MTN VALLEYS AND WHERE HEAVY RAIN FALLS
TONIGHT. WINDS MAY FLIP DIRECTION FOR A TIME IN THE WAKE OF TSRA
WINDS, WITH SITES FLIPPING TO NW WHOLESALE FRI MORNING.
OUTLOOK: AN UNSETTLED PATTERN WILL LINGER INTO EARLY NEXT WEEK
KEEPING CHANCES FOR SHOWERS AND THUNDERSTORMS AROUND AS WELL AS
ASSOCIATED RESTRICTIONS.
CLIMATE
RECORDS FOR 05-10
MAX TEMPERATURE MIN TEMPERATURE
STATION HIGH LOW HIGH LOW
------- ---------- ---------- ---------- ----------
KAVL 89 1936 53 1924 65 1927 32 2020
1896 1966
1906
KCLT 94 1896 59 1966 70 1927 38 1906
1889
KGSP 96 1889 56 1924 71 1895 32 1906
RECORDS FOR 05-11
MAX TEMPERATURE MIN TEMPERATURE
STATION HIGH LOW HIGH LOW
------- ---------- ---------- ---------- ----------
KAVL 89 1889 50 1960 64 1890 30 1966
KCLT 95 1916 58 1924 70 1889 39 1977
1896
1889
KGSP 96 1889 59 1924 69 1963 33 1906
RECORDS FOR 05-12
MAX TEMPERATURE MIN TEMPERATURE
STATION HIGH LOW HIGH LOW
------- ---------- ---------- ---------- ----------
KAVL 88 1980 44 1960 65 1918 36 1969
1956
1914
KCLT 94 1889 56 1960 69 1896 36 2020
KGSP 99 1916 56 1960 68 1979 38 2020
1933 1989
GSP WATCHES/WARNINGS/ADVISORIES
GA...NONE.
NC...NONE.
SC...NONE.
SYNOPSIS...WIMBERLEY
NEAR TERM...WIMBERLEY
SHORT TERM...MPR
LONG TERM...MPR
AVIATION...WIMBERLEY
CLIMATE...GSP
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