413
FXUS62 KGSP 081752
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
152 PM 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 150 PM EDT THURSDAY: PEAK HEATING CU CONTINUES TO GROW IN
COVERAGE ACROSS THE AREA. RADAR IS STILL CLEAR SO FAR, BUT THE
ENVIRONMENT IS IN PLACE FOR SEVERE WEATHER TO DEVELOP LATER THIS
AFTERNOON. SO MUCH SO THAT THE STORM PREDICTION CENTER HAS EXPANDED
THE SLIGHT RISK TO COVER ALL OF THE WESTERN CAROLINAS AND NORTHEAST
GEORGIA. THE FORECAST REMAINS ON TRACK WITH ONLY MINOR TWEAKS MADE
BASED ON CURRENT OBSERVATIONS AND LATEST MODEL TRENDS.
OTHERWISE, 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 /18Z THURSDAY THROUGH TUESDAY/
AT KCLT AND ELSEWHERE: DIURNAL CU WITH VERY LOW VFR CIGS CONTINUE
TO ROAM THE SKY IN ANTICIPATION OF A SHRA/TSRA DEVELOPING AFTER 19Z
IN THE MOUNTAINS AND PUSHING EAST ACROSS THE REST OF THE AREA BY
00Z, MAYBE A LITTLE AFTER. PLACED A TEMPO GROUP AT ALL TAF SITES
TO FORECAST THE BEST TIMING FOR TSRA AND ASSOCIATED RESTRICTIONS
AT EACH TERMINAL. STRONG WINDS (=> 30 KTS) AND LARGE HAIL (=>
1") ARE POSSIBLE THROUGH THE AFTERNOON AND EVENING. EXPECT THE
COVERAGE IN SHRA/TSRA TO DWINDLE AROUND 06Z OR SO. MODEL GUIDANCE
STILL HINT AT RESTRICTIONS FORMING OVERNIGHT THROUGH MID-MORNING
WITH IFR/MVFR CIGS/VSBY. THERE ARE UNCERTAINTIES FOR THE OVERALL
EXTENT OF RESTRICTIONS, BUT WITH THE POTENTIAL FOR HEAVY RAINFALL,
GROUND FOG COULD BECOME AN ISSUE TO GO ALONG WITH LOW STRATUS. MOST
VSBY/CIG RESTRICTIONS SHOULD SCATTER AROUND MID TO LATE FRIDAY
MORNING. WINDS CONTINUE OUT OF THE WEST TO SOUTHWEST THIS AFTERNOON,
WHILE LIKELY BECOMING VARIABLE WITH ANY THUNDERSTORM THAT PASSES
BY. WINDS SHOULD TOGGLE MORE WEST TO NORTHWESTERLY ON FRIDAY AS
ANOTHER ROUND OF SHRA/TSRA AND ASSOCIATED RESTRICTIONS ARE POSSIBLE
JUST AFTER THE END OF THE 18Z TAF UPDATE.
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...CAC/WIMBERLEY
SHORT TERM...MPR
LONG TERM...MPR
AVIATION...CAC
CLIMATE...
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