737
FXUS62 KGSP 300740
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
340 AM EDT SUN MAR 30 2025
SYNOPSIS
SHOWER AND THUNDERSTORM CHANCES INCREASE TODAY AS COLD FRONT
APPROACHES FROM THE WEST. THE FRONT WILL CROSS THE AREA MONDAY,
BRINGING THE POTENTIAL FOR STRONG TO SEVERE STORMS. DRY HIGH
PRESSURE RETURNS TUESDAY, THEN BECOMES ESTABLISHED OFF THE EAST
COAST, RESULTING IN WELL ABOVE NORMAL TEMPERATURES ACROSS THE
REGION LATE IN THE WEEK.
NEAR TERM /THROUGH TONIGHT/
AS OF 300 AM: EXPANSIVE HIGH PRESSURE REMAINS OVER THE WESTERN
ATLANTIC. MEANWHILE A SLOWLY STRENGTHENING SFC LOW AND ATTENDANT
SHORTWAVE WILL MOVE INTO THE UPPER MISSISSIPPI VALLEY, ON TRACK TO
PASS BY WELL TO OUR NORTHWEST. OUR CWA AND POINTS SOUTH WILL BE
MORE OR LESS IN THE WARM SECTOR OF THE LOW THROUGH THE NEAR TERM
PERIOD AND INTO MONDAY, FOR THAT MATTER. VERY LITTLE IN THE WAY
OF DYNAMIC FORCING WILL BE AT WORK IN OUR AREA THIS MORNING. WEAK
WARM UPGLIDE IS ONGOING NOW AND WILL AMPLIFY THROUGH THE MORNING;
MIDLEVEL CLOUD COVER ALREADY HAS DEVELOPED OVER OUR NW HALF,
AND SOME LIGHT HIGH-BASED SHOWERS ARE DEVELOPING OVER THE UPPER
TN VALLEY. THE BETTER MOISTURE/FORCING WILL REMAIN WEST OF THE
MOUNTAINS THIS MORNING BUT THOSE SHOWERS MAY TRACK INTO THE NC
COUNTIES BORDERING TN. IT IS MORE QUESTIONABLE WHETHER UPGLIDE
WILL BE STRONG ENOUGH OVER OUR WESTERN CWA TO SEE SHOWERS DEVELOP
IN SITU THIS MORNING. ISENTROPIC OMEGA FIELDS ARE NOT ALL THAT
IMPRESSIVE PARTLY ON ACCOUNT OF ONLY 20-25 KT WINDS AT 850 MB.
THE PRIMARY SOURCE OF LIFT THROUGH DAYBREAK WILL REMAIN MECHANICAL
LIFT AGAINST SOUTH-FACING RIDGES OF THE SW MOUNTAINS, NAMELY THE
BLUE RIDGE ESCARPMENT, MORE LIKELY TO RESULT IN DRIZZLE THAN TRUE
SHOWERS. MODELS HAVE SOMEWHAT SLOWED THE DEVELOPMENT OF SATURATED
PROFILES OVER THE CWA; CAMS ARE NO MORE RESPONSIVE WITH QPF THAN
THEY HAD BEEN LAST NIGHT IN THIS SETUP. LOWERED POPS OVER MUCH
OF THE WESTERN HALF OF THE CWA THIS MORNING, EXCEPT ALONG THE
RIDGES. LOW CLOUDS WILL INCREASE IN COVERAGE TOWARD DAYBREAK IN
THOSE AREAS, EXPANDING EASTWARD SUCH THAT TODAY WILL BE GENERALLY
CLOUDY.
MAX TEMPS WILL BE COOLER THIS AFTERNOON ON THAT NOTE AND WITH
REDUCED THICKNESSES OWING TO FALLING HEIGHTS, BUT STILL SEVERAL
DEGREES ABOVE NORMAL. INSTABILITY WILL DEVELOP DIURNALLY, LIKELY
TO THE TUNE OF 100-500 J/KG SBCAPE, PERHAPS EVEN HIGHER. DEWPOINTS
RISE INTO THE UPPER 50S TO NEAR 60 IN THE PIEDMONT. AS THE LOW
MOVES TOWARD THE GREAT LAKES AND MAKES ITS NEAREST PASS TO THE
AREA, UPGLIDE APPEARS TO STRENGTHEN OVER THE CWA, IN WHAT MIGHT
BE TERMED A SECONDARY WARM FRONT. THESE TWO ASPECTS APPEAR KEY FOR
POPS TO INCREASE EAST OF THE MOUNTAINS. MOST CAMS DEPICT SHOWERS
DEVELOPING/TRACKING FROM SW TO NE ACROSS THE CWA FROM AFTERNOON
THRU EVENING. LIKELY WORDING IS INCLUDED IN MOST AREAS WEST OF
US 221 BY LATE AFTERNOON, AND TO 30-50% IN AREAS EAST. SEVERE
WEATHER IS NOT ANTICIPATED DUE TO LACK OF DRY AIR ALOFT AND WITH
SHEAR UNREMARKABLE.
THE MECHANICAL LIFT PEAKS AS FLOW AMPLIFIES THIS EVENING BEFORE
VEERING TO A LESS FAVORABLE DIRECTION FOR OUR EASTERN ESCARPMENT
WITH THE APPROACH OF THE TROUGH, BUT UPGLIDE WILL CONTINUE. POPS
TREND DOWN IN THE EAST BUT REMAIN ELEVATED ALONG THE SW MTN RIDGES
AND SOUTH-FACING ESCARPMENT. WIDESPREAD LOW CLOUDS ARE EXPECTED
TONIGHT WHICH ALONG WITH THE HIGH DEWPOINTS WILL RESULT IN MIN
TEMPS IN THE LOWER 60S THRU THE NIGHT ACROSS MOST OF THE PIEDMONT,
AND 50S FOR THE MOUNTAIN VALLEYS. MORNING MINS MAY BE NEAR THE
DAILY HI-MIN RECORD, BUT COOLER TEMPS MAY ARRIVE BEFORE MIDNIGHT
MON NIGHT SO RECORDS ARE NOT NECESSARILY IN JEOPARDY.
SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/
KEY MESSAGES:
1) STRONG TO SEVERE THUNDERSTORMS POSSIBLE MONDAY WITH A COLD
FRONT CROSSING THE AREA.
2) DRY WEATHER RETURNS TUESDAY WITH RAIN CHANCES INCREASING
BY MIDWEEK.
AS OF 300 AM SUNDAY: THE LATEST GUIDANCE HAS COME INTO PRETTY GOOD
AGREEMENT THAT CONVECTION ASSOCIATED WITH AN APPROACHING COLD
FRONT WILL STILL BE JUST WEST OF THE FORECAST AREA 12Z MONDAY,
AND WITH THIS SLIGHTLY LATER TIMING, INCREASES THE CONFIDENCE THAT
CONVECTION WILL HAVE SOME INSTABILITY TO WORK WITH AS IT CROSSES
THE FORECAST AREA LATER IN THE DAY. THE WINDOW FOR SEVERE STORMS
APPEARS TO BE FROM AROUND MIDDAY TO EARLY EVENING MONDAY, WITH
STORMS TRACKING FROM WEST TO EAST. SOME OF THE CAMS STILL SUGGEST
THAT A LINE OF STORMS COULD RACE OUT AHEAD OF THE FRONT AND PUSH
INTO THE NC MOUNTAINS BEFORE DAYBREAK, BUT THE ACTIVITY WEAKENS
SIGNIFICANTLY AND DOESN'T LOOK VERY ROBUST. THE 00Z HRRR SHOWS
THE LINE OF CONVECTION STRENGTHENING OVER AL/GA, ENTERING OUR GA
COUNTIES AROUND NOON. FROM THERE, STORMS LOOK TO FAVOR A LINEAR
MODE, WITH DAMAGING WIND GUSTS BEING THE MAIN THREAT. BUT SOME
DISCRETE STORMS MAY FORM AHEAD OF THE LINE, AND SOME EMBEDDED
SUPERCELLS MAY FORM IN THE LINE, BOTH OF WHICH MAY PRODUCE A
LARGE HAIL AND TORNADO THREAT. LOW-LEVEL SHEAR (30+ KT OF 0-1 KM
SHEAR AND 0-3KM SRH 200-300 M2/S2)LOOKS ADEQUATE FOR TORNADOES,
ESPECIALLY ACROSS THE PIEDMONT. THE CONVECTION WILL HAVE GOOD
UPPER SUPPORT WITH A DYNAMIC UPPER TROUGH CROSSING THE AREA. SPC
HAS UPGRADED THE RISK TO ENHANCED FOR ALL OF OUR FOOTHILLS AND
PIEDMONT ZONES, MAINLY DUE TO INCREASED TORNADO THREAT. QPF LOOKS
TO BE GENERALLY 0.25"-0.5", WITH HIGHER AMOUNTS POSSIBLE IN THE
SW-FACING SLOPES OF THE MOUNTAINS. THUNDERSTORMS SHOULD PUSH EAST
OF THE AREA EARLY IN THE EVENING, WITH LINGERING SHOWERS POSSIBLE,
MAINLY IN THE MOUNTAINS AS THE UPPER TROUGH PASSES.
CAA BEHIND THE FRONT SHOULD BRING TEMPS BACK DOWN TO NEAR NORMAL
MONDAY NIGHT THRU TUESDAY, AS HIGH PRESSURE NOSES IN FROM THE
NORTH. DRY AIR WILL BRING RH BACK DOWN INTO THE 25-35% RANGE
TUESDAY AFTN, WITH LIGHT WINDS.
LONG TERM /WEDNESDAY THROUGH SATURDAY/
KEY MESSAGES
1) THE FORECAST HAS TRENDED DRIER IN THE MEDIUM RANGE, AS A STRONG
RIDGE BUILDS ACROSS THE SOUTHEAST
2) TEMPERATURES WARM TO WELL ABOVE NORMAL THROUGH THE PERIOD.
AS OF 140 AM SUNDAY: THE MEDIUM RANGE WILL BE DOMINATED BY A STRONG
UPPER RIDGE THAT WILL BUILD OVER THE SOUTHEAST THRU THE END OF THE
WEEK. THE 00Z GUIDANCE HAS TRENDED STRONGER WITH THE RIDGE, AND THIS
LOOKS TO SUPPRESS PRECIP CHANCES, DESPITE AN INCREASE IN HUMIDITY
WITHIN A SOUTHERLY TO SOUTHWESTERLY FLOW REGIME. WEDNESDAY WILL HAVE
THE BEST RAIN CHANCES, AS A WARM FRONT OF SORTS LIFTS NORTH THRU THE
AREA. THERE WILL BE A FEW HUNDRED J/KG OF CAPE TO SUPPORT A FEW
EMBEDDED THUNDERSTORMS IN WHATEVER CONVECTION MAY DEVELOP, BUT THE
SEVERE THREAT SHOULD BE LOW AS FORCING WON'T BE STRONG. THE LATEST
NBM STILL HAS SLGT CHC TO CHC POPS THURSDAY, ESPECIALLY IN THE
MOUNTAINS, BUT IF MODEL TRENDS HOLD, THESE WILL LIKELY BE LOWERED IN
LATER FORECASTS. FRIDAY AND SATURDAY LOOK LARGELY DRY, AS THE UPPER
HIGH WILL BE AT ITS STRONGEST AND DRIFTS WESTWARD TOWARD FL. THE
BIGGEST STORY WILL LIKELY BE THE UNUSUALLY WARM TEMPS FOR EARLY
APRIL. HIGHS MAY REACH THE UPPER 80S FRIDAY IN THE I-85 CORRIDOR AND
SOUTHEAST. LOWS WILL LIKELY BE IN THE LOW TO MID 60S EACH NIGHT
OUTSIDE THE MOUNTAINS. DEWPTS WILL CREEP INTO THE 50S TO LOWER 60S,
WHICH WILL HELP KEEP RH ABOVE CRITICAL LEVELS FOR WILDFIRE RISK.
AVIATION /08Z SUNDAY THROUGH THURSDAY/
AT KCLT AND ELSEWHERE: CLOUD DECK WITH BASES 050-120 ALREADY
PRESENT OVER THE TERMINALS, WITH A FEW LOWER VFR CLOUDS SCATTERED
UNDERNEATH, IN CONJUNCTION WITH WARM UPGLIDE OCCURRING ALOFT. A
FEW LIGHT RETURNS ARE SEEN ON RADAR OVER THE NC MOUNTAINS, PROBABLY
SPRINKLES WITH MINIMAL IMPACT, BUT SCT SHRA WILL BECOME INCREASINGLY
POSSIBLE OVER KAVL TOWARD DAYBREAK, AND BY LATE MORNING AT THE OTHER
TERMINALS, EXCEPTING KCLT. MVFR TO IFR CIGS ARE LIKELY TO DEVELOP
ALONG THE SOUTH-FACING RIDGES BEFORE DAYBREAK ALSO, AND THEN AT
KAVL AND THE SC SITES BY 11-15Z. A SECONDARY WARM FRONT ARRIVING
THIS AFTN NEAR KAND, AND PROGRESSING NE THROUGH THE EVENING, WILL
KICK OFF ANOTHER ROUND OF SHOWERS AND ISOLATED TO WIDELY SCATTERED
TSRA, WARRANTING PROB30 MENTION AT ALL SITES. TSRA MAY PRODUCE
IFR CIGS WHICH MAY NOT IMPROVE AFTERWARD. SHRA MAY DECREASE IN
COVERAGE AFTER 06Z BUT WIDESPREAD IFR IS EXPECTED TO REMAIN IN
PLACE THRU DAYBREAK MON. CONTINUED S TO SSW WINDS WITH 15-20 KT
GUSTS POSSIBLE THIS AFTN.
OUTLOOK: SHRA/TSRA AND ASSOCIATED RESTRICTIONS POSSIBLE ON MONDAY.
DRYING IS EXPECTED ON TUESDAY. SOME LIGHT PRECIP IS POSSIBLE BY
THURSDAY, BUT MORE LIKELY NOT UNTIL NEXT WEEKEND.
GSP WATCHES/WARNINGS/ADVISORIES
GA...NONE.
NC...NONE.
SC...NONE.
SYNOPSIS...ARK
NEAR TERM...WIMBERLEY
SHORT TERM...ARK
LONG TERM...ARK
AVIATION...WIMBERLEY
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