860
FXUS62 KGSP 082159
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
559 PM EDT THU MAY 8 2025
SYNOPSIS
A COLD FRONT CROSSES THE AREA FRIDAY AND STALLS OVER THE SOUTHEAST
THIS WEEKEND INTO EARLY NEXT WEEK, KEEPING UNSETTLED WEATHER AROUND
THROUGH THEN. THE FRONT AND ASSOCIATED LOW PRESSURE SYSTEM FINALLY
CLEARS THE AREA THURSDAY.
NEAR TERM /THROUGH FRIDAY/
AS OF 555 PM EDT THURSDAY: MAIN CHANGE NEEDED THIS UPDATE WAS
INCREASING POPS AND THUNDER CHANCES WHERE CONVECTION IS CURRENTLY
ONGOING PER THE LATEST GSP RADAR MOSAIC...AND THROUGH THE NEXT FEW
HOURS BASED ON THE LATEST 18Z CAMS. A SEVERE THUNDERSTORM WATCH
REMAINS IN EFFECT THROUGH MIDNIGHT ACROSS THE ENTIRE FORECAST AREA
AS STRONG TO SEVERE STORMS ARE CURRENTLY ONGOING ACROSS WESTERN NC
AND EXTREME NE GA. WITH 1,500-2,000 J/KG OF SBCAPE AND 35-45 KTS OF
EFFECTIVE SHEAR IN PLACE ACROSS THE FORECAST AREA, THE MAIN HAZARDS
ARE LARGE HAIL (UP TO 2") AND DAMAGING WIND GUSTS (UP TO 70 MPH).
ACTIVITY SHOULD REMAIN CONFINED TO THE NORTHERN ZONES THROUGH ~00Z
BEFORE COVERAGE OF STORMS INCREASES ACROSS THE SOUTHERN ZONES AFTER
00Z AND THROUGH LATE TONIGHT.
OTHERWISE, ELONGATED UPPER TROUGH AND ASSOCIATED HEIGHT FALLS
STRETCH FROM THE EASTERN ATLANTIC CANADA THROUGH THE GREAT LAKES AND
INTO THE OZARKS. THIS IS HELPING TO SEND AN ATTENDANT COLD FRONT
TOWARDS THE REGION, WITH THE BEST FORCING ENCROACHING THE CFWA AND
SHOULD EXIST OVER THE AREA THROUGH THIS EVENING. DISCRETE CELLS WILL
DEVELOP INITIALLY WITH ROBUST SUPERCELL FEATURES. STEEP AND DRIER
LOW/MID-LEVEL LAPSE RATES AND LOWER THAN NORMAL FREEZING LEVEL
(~10,000') SUGGEST THE ONSET THREAT WILL BE LARGE HAIL, WITH
ISOLATED CONVECTION CAPABLE OF PRODUCING HAIL OF 2" OR GREATER AND
DOWNBURSTS (DCAPE 600-800 J/KG), MAINLY ACROSS THE NORTH CAROLINA
MOUNTAINS/FOOTHILLS. AS THE ACTIVITY PUSHES EAST, CAMS CONTINUE TO
SHOW UPSCALE GROWTH AND THE DEVELOPMENT OF A COLD POOL INTO THE
EVENING HOURS ACROSS THE NORTH CAROLINA PIEDMONT AND NORTHERN
UPSTATE TO HELP AID IN STORM INITIATION DOWNSTREAM FROM THE ORIGINAL
STARTING POINT. STORM MODE BECOMES MORE LINEAR AND ALLOWS FOR THE
HAIL THREAT TO DIMINISH, BUT UPTICKS THE DAMAGING WIND THREAT AS THE
CONVECTION PUSHES FURTHER EAST. CAMS ALSO DEPICT ANOTHER AREA OF
INTEREST ACROSS THE UPSTATE AND NORTHEAST GEORGIA AS THE CONVECTION
FROM TENNESSEE AND NORTHERN PORTIONS OF THE DEEP SOUTH GROW UPSCALE
AND MAKE A RUN AT THE SOUTHERN HALF OF THE CFWA, WHERE THE
ENVIRONMENT MAY BE LEFT UNTAPPED. STORM MODE WOULD BE MORE LINEAR IN
THIS CASE AND LOOK FOR THE THREAT TO BE MAINLY DAMAGING WINDS. IN
BOTH CASES WHEN THE STORM MODE SHIFTS MORE LINEAR, HODOGRAPHS BECOME
A LITTLE MORE DEEPER AS THE LLJ (15-25 KTS) IS BETTER ESTABLISHED
LATER THIS EVENING. IN THIS CASE, A TORNADO OR TWO CAN'T BE RULED
OUT, BUT THE LACK OF LOW-LEVEL SHEAR WILL MAKE TORNADOGENESIS
DIFFICULT.
THE COLD FRONT TO THE NORTHWEST OF THE AREA WILL STRUGGLE TO REACH
THE CFWA UNTIL FRIDAY AFTERNOON AS THE UPPER-LEVEL PATTERN AMPLIFIES
WITH THE TROUGH DEVELOPING A CLOSED UPPER LOW AND SLOWS DOWN THE
FRONTAL BOUNDARY ADVANCEMENT. AS A RESULT, LINGERING CONVECTION
WILL BE POSSIBLE OVERNIGHT AS MODEL GUIDANCE STRUGGLE TO FULLY
GET RID OF ELEVATED CAPE AND OVERALL FORCING. CONVECTIVE DEBRIS
WILL LIKELY LINGER THROUGH MUCH OF THE NIGHTTIME PERIOD, BUT IF
SOME CLEARING CAN GET GOING EXPECT AREAS OF FOG AND POSSIBLY LOW
STRATUS TO SETTLE IN JUST BEFORE DAYBREAK.
THE NOW CLOSED UPPER LOW WILL INTENSIFY AND SET UP SHOP OVER THE
MID-ATLANTIC BY FRIDAY AS THE FRONT GRADUALLY ENTERS THE CFWA FROM
THE NORTHWEST BY LATE MORNING TO EARLY AFTERNOON FRIDAY. ANOTHER
ROUND OF CONVECTION IS EXPECTED AHEAD OF THE FRONT DURING PEAK
HEATING FRIDAY. CAMS ARE NOT AS EXCITED WITH THIS POTENTIAL,
BUT STILL SHOW AN ENVIRONMENT CONDUCIVE FOR MULTI-CELLULAR TO
SUPERCELLULAR STORM MODE AS 25-35 KTS OF SHEAR AND 1000-2000 J/KG
OF MLCAPE DEVELOP. THE OVERALL FORCING ISN'T THE BEST, HOWEVER,
INVERTED-V PROFILES AND DRY MID-LEVEL INDICATE DAMAGING WINDS WILL
BE THE MAIN THREAT, BUT LARGE HAIL CAN'T BE RULED OUT. COVERAGE
WILL BE MORE ISOLATED COMPARED TO TODAY, BUT THE SEVERE THREAT WILL
PERSIST NONETHELESS AS THE COLD FRONT MOVES ACROSS THE AREA DURING
PEAK HEATING FRIDAY. AFTERNOON HIGHS WILL END UP A FEW DEGREES ABOVE
NORMAL AHEAD OF THE FRONT, BUT COOLER THAN NORMAL FOR LOCATIONS
BEHIND THE FRONT (MAINLY ACROSS THE MOUNTAINS) DURING PEAK HEATING.
SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/
AS OF 200 PM EDT THURSDAY: ANY LEFT OVER CONVECTION WILL QUICKLY
DISSIPATE WITH LOSS OF HEATING FRIDAY EVENING AS DRIER AND COOLER
HIGH PRESSURE BUILDS IN FROM THE NORTH AND THE FRONTAL BOUNDARY
MOVES SOUTH OF THE AREA. LOWS NOW LOOK TO DROP TO NEAR OR 5 DEGREES
BELOW NORMAL.
GUIDANCE CONTINUES TO TREND DRIER FOR SATURDAY AS THE DRIER AIR MASS
AND SURFACE HIGH PENETRATE FARTHER INTO THE SOUTHEAST. EVEN WITH
THOSE EXPECTATIONS, THERE MAY BE SOME SHOWERS OVER THE LAKELANDS
INTO THE UPPER SAVANNAH RIVER VALLEY AS MOISTURE MAY TRY TO LIFT
NORTH OVER THE STALLED FRONTAL BOUNDARY. EVEN IF THAT OCCURS, ANY
PRECIP WILL BE VERY LIGHT. DESPITE THE COOLER AIR MASS, THE LACK OF
PRECIP WILL ALLOW TEMPS TO WARM MORE THAN PREVIOUSLY EXPECTED AS NO
REAL COLD AIR DAMMING DEVELOPS. HIGHS WILL STILL BE AROUND 5 DEGREES
BELOW NORMAL.
THIS DRIER TREND CONTINUES INTO SUNDAY WITH PRECIP SLOWER TO MOVE
BACK NORTH AS THE MOIST LOW LEVEL FLOW AND ISENTROPIC LIFT TAKE
LONGER TO DEVELOP IN RESPONSE TO THE DEVELOPING UPPER LOW AND
ASSOCIATED SURFACE LOW NEAR THE GULF COAST REMAINING FARTHER SOUTH
AND WEST OF THE AREA. STILL HAVE A CHANCE OF SHOWERS MOVING INTO NE
GA AND THE UPSTATE BY AFTERNOON WITH SLIGHT CHANCE OVER NC. BUT
AGAIN, ANY PRECIP WOULD BE LIGHT. THE LACK OF PRECIP KEEPS THE CAD
FROM FORMING AND ALLOWING TEMPS TO WARM MORE THAN PREVIOUSLY
EXPECTED. DIDN'T GO FULL ON WITH THE MODEL BLEND GIVEN THE
UNCERTAINTY, BUT HIGHS END UP AROUND 5 DEGREES BELOW NORMAL BUT
COULD BE WARMER IF THE PRECIP REMAINS SLOW TO DEVELOP.
LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/
AS OF 230 PM EDT THURSDAY: WIDESPREAD PRECIP DOES BEGIN MOVING BACK
INTO THE AREA SUNDAY NIGHT AS THE STACKED LOW PRESSURE SYSTEM BEGINS
MOVING NORTH AND A STRONGER, MOIST LOW LEVEL SOUTHERLY FLOW AND
ISENTROPIC LIFT DEVELOP. THIS DOES HELP THE HYBRID COLD AIR DAMMING
TO SET IN BY MONDAY AND HOLDING ON THROUGH MONDAY NIGHT AS PRECIP
CONTINUES. THE CAD ERODES TUESDAY AS THE HIGH MOVES WELL OFF SHORE
CUTTING OFF SUPPORT FOR THE CAD AND THE STACKED LOWS MOVE NORTH AND
EAST. WIDESPREAD PRECIP REMAINS OVER THE AREA THOUGH WITH THE
STRONG, MOIST SOUTHERLY FLOW AND ISENTROPIC LIFT. THE LOWS ONLY
SLOWLY MOVE NORTHEAST ON WEDNESDAY KEEPING MOISTURE AND PRECIP OVER
THE AREA THROUGH THE DAY. THE LOWS FINALLY MOVE NORTHEAST OF THE
AREA ON THURSDAY, BUT SOME LINGERING NW FLOW SHOWERS MAY CONTINUE.
THERE IS A THREAT OF MODERATE TO HEAVY RAINFALL WITH THIS SYSTEM.
THE GUIDANCE HAS POOR RUN TO RUN CONSISTENCY OF QPF HOWEVER. IN
FACT, OVERALL PRECIP WILL LIKELY BE ON THE LOWER SIDE OF GUIDANCE
GIVEN THE NOW DRIER SHORT TERM. STILL, SOME EXCESSIVE RAINFALL AND
MINOR FLOODING CAN'T BE RULED OUT. THERE WILL BE SOME THUNDERSTORMS
ONCE THE CAD ERODES, BUT CHANCE OF SEVERE STORMS LOOKS QUITE LOW FOR
NOW.
HIGHS WILL BE AROUND 10 DEGREES BELOW NORMAL MONDAY IN THE CAD, THEN
SLOWLY WARMING TO NEAR NORMAL BY WED AND ABOVE NORMAL BY THURSDAY.
AVIATION /22Z 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...RWH
NEAR TERM...AR/CAC
SHORT TERM...RWH
LONG TERM...RWH
AVIATION...CAC
CLIMATE...GSP
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