861
FXUS62 KGSP 090800
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
400 AM EDT FRI MAY 9 2025
SYNOPSIS
A COLD FRONT SHOULD CROSS THE AREA TODAY AND THEN STALL OVER
THE SOUTHEAST THIS WEEKEND. DRY AIR WILL BRIEFLY MOVE IN TONIGHT
AND SATURDAY. BY SUNDAY, AN UPPER LOW WILL DEVELOP TO OUR WEST,
BRINGING RAIN BACK UP FROM THE SOUTH. THE SLOW MOVEMENT OF THIS
SYSTEM WILL KEEP RAINY AND UNSETTLED WEATHER AROUND THROUGH THE
FIRST HALF OF NEXT WEEK.
NEAR TERM /THROUGH TONIGHT/
AS OF 315 AM EDT FRIDAY: AN UPPER LOW DIPS INTO THE EASTERN GREAT
LAKES, WHILE ANOTHER LOW BEGINS TO CLOSE OFF OVER THE LOWER MS
VALLEY. AT THE SFC, A COLD FRONT ASSOCIATED WITH LOW PRES OVER
THE MID-ATLANTIC WILL PUSH THRU THE CWFA FROM THE NW TODAY. IN THE
MEANTIME, THERE IS STILL ONGOING CONVECTION ACROSS THE SOUTHEAST
EDGE OF THE FORECAST AREA. THIS ACTIVITY SHOULD GRADUALLY DIMINISH
THRU THE PRE-DAWN HOURS. SKIES ARE CLEARING TO THE WEST, AND PATCHY
FOG AND LOW STRATUS IS ALREADY FORMING IN THE MOUNTAIN VALLEYS AND
PORTIONS OF THE UPSTATE. THIS WILL LIKELY CONTINUE TO EXPAND THRU
DAYBREAK, AS THE CONVECTIVE DEBRIS CLOUDS CLEAR AND RADIATIONAL
COOLING IMPROVES.
THRU MIDDAY, THE FOG AND STRATUS SHOULD LIFT AND SCATTER INTO A
CU FIELD. THE 00Z CAMS LINE UP WITH THE GFS/NAM/CANADIAN ON JUST
ISOLATED TO WIDELY SCATTERED CONVECTION FORMING ALONG THE FRONT
AS IT APPROACHES THE BLUE RIDGE ESCARPMENT AROUND MIDDAY OR EARLY
AFTN. THIS ACTIVITY WILL THEN TRACK THRU THE PIEDMONT AND CLEAR TO
OUR SE BY EARLY EVENING. WE WILL HAVE 35-40 KT OF 0-6KM BULK SHEAR,
BUT INSTABILITY WILL BE LESS THAN YESTERDAY, WITH GENERALLY 1500
J/KG OF SBCAPE OR LESS. SO THE SEVERE THREAT SHOULD BE LIMITED
TO MARGINAL LARGE HAIL AND DAMAGING WIND THREAT ALONG THE FAR SE
EDGE OF THE CWFA. HIGHS WILL BE A CATEGORY ABOVE NORMAL EAST OF
THE MOUNTAINS AND NEAR NORMAL IN THE MOUNTAINS.
SFC HIGH PRES WILL NOSE IN FROM THE OH VALLEY TONIGHT, HELPING
CLEAR THE SKIES AND ALLOW TEMPS TO FALL TO NEAR OR SLIGHTLY BELOW
NORMAL. THERE WILL BE INCREASING HIGH CLOUDS FROM THE SOUTH, AS
THE UPPER LOW DEEPENS OVER THE LOWER MS VALLEY. IF SOME LOW-LEVEL
MOISTURE CAN BE TAPPED WITH AN EASTERLY FLOW, CLOUD COVER MAY END
UP THICKER AND KEEP MIN TEMPS UP, ESPECIALLY IN THE SOUTHERN HALF
OF THE FORECAST AREA.
SHORT TERM /SATURDAY THROUGH SUNDAY/
AS OF 340 AM EDT FRIDAY: COOL HIGH PRESSURE SHOULD BUILD INTO THE
REGION FROM THE NORTHWEST ON SATURDAY, BUT CLOUD COVER IS EXPECTED
TO REMAIN EXTENSIVE AS A MID/UPPER LOW GRADUALLY SPINS UP AND
DEEPENS OVER THE MS DELTA REGION. THERE REMAINS MUCH UNCERTAINTY
AS TO HOW FAR NORTH LIGHT PRECIP WILL BE ABLE TO DEVELOP DURING
THE DAY AS IT WILL BE FIGHTING TO OVERCOME THE DRY AIR MOVING
IN FROM THE NW AND N, THUS WE WILL KEEP A GRADIENT BETWEEN AREAS
EXPECTED TO REMAIN DRY NORTH OF I-40 AND AREAS TO THE SOUTH ACROSS
THE LAKELANDS WHICH MAY SEE SOME RAIN BY AFTERNOON. TEMPS WILL
BE HELD AT LEAST FIVE DEGREES UNDER NORMAL. UNCERTAINTY CLIMBS
THRU THE WEEKEND WITH REGARD TO HOW QUICKLY PRECIP WILL DEVELOP
NORTHWARD AS THE UPPER LOW CONTINUES TO DEVELOP OVER LOUISIANA. A
REX BLOCK PATTERN MAY FORM TO OUR WEST ON SUNDAY, SUPPORTING HIGH
PRESSURE MOVING PAST TO OUR NORTH. SHOULD THE LIGHT PRECIP MAKE
IT FAR ENOUGH NORTH, A HYBRID COLD AIR DAMMING WEDGE COULD DEVELOP
DURING SUNDAY THAT WOULD KEEP TEMPS ABOUT TEN DEGREES BELOW NORMAL
WITH EXTENSIVE CLOUD COVER. AT LEAST THERE'S GOOD AGREEMENT WITH
THE DEVELOPMENT OF THE MID/UPPER LOW IN THE 00Z GUIDANCE.
LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/
AS OF 230 AM EDT FRIDAY: LOOKS LIKE A FAVORABLE SETUP FOR HEAVY
RAIN ACROSS THE FCST AREA DURING THE FIRST HALF OF NEXT WEEK AS
THE OPERATIONAL MODEL SOLUTIONS ARE IN REASONABLE AGREEMENT WITH
LIFTING A MID/UPPER LOW FROM THE MS DELTA REGION ON MONDAY SLOWLY
NORTHEASTWARD TO THE OH VALLEY REGION TUESDAY NIGHT. MONDAY AND
MONDAY NIGHT APPEAR TO HAVE THE BEST SIGNAL IN THE GFS, WITH GOOD
UPPER DIVERGENCE MOVING NORTHEAST ACROSS THE REGION AND A DIFLUENT
MID-LEVEL PATTERN WITH GOOD DPVA AS WELL. MEANWHILE, EXCELLENT LOW
LEVEL ISENTROPIC LIFT AND SOUTHEAST MOIST UPSLOPE FLOW AT 850MB IS
SHOWN TO IMPINGE UPON THE BLUE RIDGE ESCARPMENT. THE INGREDIENTS
FOR EXCESSIVE RAINFALL APPEAR TO BE COMING INTO ALIGNMENT, SO
IT'S HARD TO ARGUE TOO MUCH WITH THE SLIGHT RISK ON THE DAY 4
ERO. THAT BEING SAID, NO NEED TO MASH THE PANIC BUTTON JUST YET
BECAUSE THERE'S STILL ENOUGH UNCERTAINTY REGARDING THE IMPORTANT
DETAILS AND THE QPF STILL SEEMS MODEST, BUT WE SHALL BE KEEPING
AN EYE ON THE POTENTIAL. TEMPS ON MONDAY WILL REMAIN COOL WITH A
REMNANT COOL POOL HANGING ON EAST OF THE MTNS, HELD IN PLACE BY
EXTENSIVE CLOUDINESS AND PRECIP, BUT ALAS THE LAST VESTIGES OF
ANY REMAINING CAD SHOULD GET WIPED OUT TUESDAY AS A SFC LOW MOVES
THROUGH OUR VICINITY. NEEDLESS TO SAY, WE WILL CONTINUE TO CARRY
LIKELY TO CATEGORICAL PRECIP PROBS THRU TUESDAY NIGHT OR UNTIL THE
UPPER LOW LIFTS OUT FAR ENOUGH NE TO PUSH THE TROF AXIS OVERHEAD
ON WEDNESDAY. WITH THAT SYSTEM OUT OF THE WAY FINALLY WEDNESDAY
NIGHT, THE SECOND HALF OF THE WEEK SHOULD FEATURE A RETURN TO
SOMETHING MORE NORMAL AS THE PATTERN BECOMES MORE PROGRESSIVE AND
UPPER RIDGING IS ESTABLISHED OVER THE SOUTHEAST. TEMPS WARM UP
ABOVE NORMAL BY THURSDAY AND FRIDAY IN RESPONSE, WITH A PRECIP
PROB DISTRIBUTION MORE LIKE CLIMO.
AVIATION /08Z FRIDAY THROUGH TUESDAY/
AT KCLT AND ELSEWHERE: CONVECTION WILL LINGER ACROSS THE AREA
THRU ABOUT 9Z, AND SHOULD MAINLY BE SHRA WITH ISOLATED TS. PLENTY
OF DEBRIS CLOUDINESS WILL HELP SLOW DOWN FOG AND LOW STRATUS
FORMATION, BUT WITH MOIST GROUND FROM EVENING RAINFALL, THERE WILL
LIKELY BE IFR RESTRICTIONS AT ALL OR MOST OF OUR TAF SITES BEFORE
DAYBREAK. THE FOG AND STRATUS SHOULD IMPROVE MID TO LATE MORNING
TO VFR. A COLD FRONT WILL PUSH INTO THE AREA FROM THE NW AND IS
EXPECTED TO TRIGGER ISOLATED TO WIDELY SCATTERED CONVECTION AS IT
CROSSES THE PIEDMONT. THE LATEST GUIDANCE TRENDED LOWER ON COVERAGE,
BUT WILL CONTINUE WITH PROB30 FOR TSRA AT KCLT AND KGSP/KGMU,
WHERE THE CHANCES WILL BE HIGHEST. WILL GO WITH SHRA AT KAVL AND
KHKY, WHICH WILL SEE THE FRONT MOVE THRU EARLIER IN THE DAY WHEN
THERE WILL BE LESS INSTABILITY. WINDS WILL SHIFT TO WNW AT KCLT
AND KHKY, BUT REMAIN WSW IN THE UPSTATE UNTIL THIS EVENING, WHEN
ALL SITES TOGGLE TO NE.
OUTLOOK: BRIEF DRYING FRIDAY NIGHT INTO SATURDAY. THEN, AN
UNSETTLED PATTERN RETURNS SATURDAY NIGHT THRU EARLY NEXT WEEK,
WITH CHANCES FOR SHOWERS AND THUNDERSTORMS AROUND AS WELL AS
ASSOCIATED RESTRICTIONS.
GSP WATCHES/WARNINGS/ADVISORIES
GA...NONE.
NC...NONE.
SC...NONE.
SYNOPSIS...PM
NEAR TERM...ARK
SHORT TERM...PM
LONG TERM...PM
AVIATION...ARK
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