960
FXUS62 KGSP 301048
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
648 AM EDT FRI MAY 30 2025
SYNOPSIS
A COLD FRONT WILL MOVE ACROSS THE AREA TODAY, WITH SHOWERS AND
THUNDERSTORMS DEVELOPING AHEAD OF THE BOUNDARY. STRONG TO SEVERE
THUNDERSTORMS ARE POSSIBLE LATER THIS MORNING AND AFTERNOON BEFORE
THE COLD FRONT MOVES EAST OF THE AREA BY THIS EVENING. A DRIER
AIRMASS WILL MOVE INTO THE REGION THIS WEEKEND, BUT A FEW SHOWERS
CAN'T BE RULED OUT, ESPECIALLY ACROSS THE MOUNTAINS. BELOW NORMAL
TEMPERATURES THROUGH THE WEEKEND WILL RISE TO A LITTLE ABOVE NORMAL
NEXT WEEK AS A WARM AND HUMID AIRMASS RETURNS.
NEAR TERM /THROUGH TONIGHT/
AS OF 645 AM EDT FRIDAY: LOW CLOUDS ACROSS THE AREA THIS MORNING
WILL LIFT BY NOON. PATCHY FOG WILL DISSIPATE SOONER.
ALL EYES THEN TURN TO THE WEST AS A LINE OF ORGANIZED CONVECTION
AHEAD OF A COLD FRONT IS EXPECTED TO MOVE INTO THE NC MOUNTAINS
AROUND NOON THEN MOVE SOUTHEAST ACROSS THE AREA THROUGH THE
AFTERNOON. THERE WILL BE PLENTY OF FORCING AS A STRONG SHORT WAVE
CROSSES THE AREA, ALONG WITH THE FRONT. STRONG BULK SHEAR IS
EXPECTED AS WELL, BUT INSTABILITY COULD BE SOMEWHAT LIMITED DUE TO
MODERATE LAPSE RATES AND MODEST HEATING WITH THE LOW CLOUDS IN PLACE
TO START THE DAY. THE CAM GUIDANCE DISAGREES ON WHETHER STORM MODE
WILL BE MORE LINEAR OR MORE DISCRETE CELLS. LOW LEVEL WINDS LOOK TO
BE LESS BACKED AS THE SURFACE LOW ALONG THE FRONT WILL BE NORTH OF
THE AREA WHICH COULD HELP KEEP STORMS MORE LINEAR OR MULTI-CELL
CLUSTERS. SHOULD THIS BE THE CASE, SEVERE MODE WOULD TREND MORE
TOWARD DAMAGING WINDS WITH ONLY ISOLATED LARGE HAIL AND TORNADOES
ASSOCIATED WITH ANY HYBRID SUPERCELLS THAT MAY DEVELOP. GIVEN ALL
THIS, THE SLIGHT RISK OF SEVERE STORMS TODAY LOOKS WELL PLACED.
OUTSIDE OF ANY STORMS, GUSTY SW WIND DEVELOPS AHEAD OF THE FRONT
TURNING W TO NW BEHIND IT. HIGHS WILL BE UP TO 5 DEGREES BELOW
NORMAL.
THE STORMS WILL HAVE MOVED EAST OF THE AREA BY EARLY EVENING WITH
CLEARING SKIES AND DIMINISHING WINDS OUTSIDE OF THE MOUNTAINS.
SCATTERED SHOWERS WILL LINGER MAINLY ACROSS THE NC NORTHERN
MOUNTAINS IN THE MOIST NW FLOW. GUSTY NW WINDS WILL REMAIN ACROSS
THE MOUNTAINS AS WELL. LOWS WILL BE AROUND 5 DEGREES BELOW NORMAL.
SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/
AS 235 AM EDT FRIDAY: BROAD CYCLONIC FLOW ALOFT AND A POST-FRONTAL
REGIME WILL BE IN STORE FOR SATURDAY AS THE NEAR-TERM COLD FRONT
WILL BE WELL OFFSHORE THE CAROLINA COAST. AS THE UPPER LOW CHURNS
OVER ATLANTIC CANADA AND NORTHEAST CONUS SATURDAY, DEEP LAYER
NORTHWESTERLY FLOW WILL BECOME BETTER ESTABLISHED. SHALLOW LAYER OF
LOW-LEVEL MOISTURE, WITH POTENTIAL GREAT LAKES CONNECTION WILL BANK
UP AGAINST THE NC/TN BORDER, WHILE MECHANICAL LIFTING PROVIDES
ENOUGH FORCING FOR SHOWERS TO DEVELOP IN THE USUAL NORTHWEST
FLOW LOCATIONS, MAINLY CONFINED TO THE NC/TN BORDER. GUIDANCE
HAS HANDLED THE EXTENT OF PRECIP DIFFERENTLY WITH SOME CAMS AND
DETERMINISTIC MODELS BREAKING CONTAINMENT ACROSS MOST OF THE NC
MOUNTAINS AND EVEN SLIPPING INTO THE FOOTHILLS AND FAR WESTERN
PIEDMONT ZONES. IN THIS CASE, CHANCE POPS (25%-54%) ARE IN PLACE
FOR THE MOUNTAIN ZONE AND SLIGHT CHANCE (15%-24%) POPS NORTH AND
WEST OF THE I-85 CORRIDOR. NOT FULLY CONVINCED ANY PRECIP WILL
SURVIVE PAST I-85 AS A RELATIVELY STOUT DOWNSLOPE COMPONENT WILL
HELP TO OFFSET MUCH ADVANCEMENT EAST OF THE BLUE RIDGE ESCARPMENT,
EVEN THOUGH BETTER UPPER-LEVEL DIVERGENCE IS PRESENT ALONG AND NORTH
OF I-40, WHERE IF SHOWERS BREAK CONTAINMENT, THAT WOULD BE THE MOST
LIKELY LOCATIONS OUTSIDE OF THE MOUNTAINS. WIND GUSTS WILL ALSO
BE ELEVATED DURING THE DAY THANKS TO 850MB FLOW COMING IN BETWEEN
20-30 KTS. TEMPERATURES ON SATURDAY ARE EXPECTED TO BE AT OR A
FEW TICKS BELOW NORMAL WITH WEAK LOW-LEVEL CAA FILTERING IN, WHILE
BEING SLIGHTLY OFFSET BY THE AFOREMENTIONED DOWNSLOPE COMPONENT.
CAN'T RULE OUT LINGERING SHOWERS ALONG THE NC/TN BORDER SATURDAY
EVENING INTO SATURDAY NIGHT, BUT THE FLOW ALOFT BECOMES MORE
WEST-NORTHWESTERLY, WHICH WOULD FAVOR MORE OF THE SLOPES NEAR
THE LOWER FRENCH BROAD VALLEY AND SMOKIES. WITH THE DOWNSLOPE
COMPONENT GRADUALLY SUBSIDING OVERNIGHT SATURDAY AND CLOUD COVER
MOST LIKELY STAYING CONFINED TO THE NC/TN BORDER, DECENT COOLING
WILL TAKE PLACE, ALTHOUGH NOT FULLY MAXIMIZING AS THE BOUNDARY LAYER
OVERNIGHT STRUGGLES TO FULLY DECOUPLE. AS A RESULT, SATURDAY NIGHT
LOWS WILL RUN A CATEGORY OR SO BELOW NORMAL. AN APPROACHING WEAK
SHORTWAVE WILL ROUND THE BASE OF THE BROAD CYCLONIC FLOW ALOFT AND
ALLOW FOR AN ENCROACHING BACKDOOR FRONT TO SLOWLY MOVE TOWARDS THE
AREA FROM THE NORTH ON SUNDAY. GUIDANCE ARE HAVING A HARD TIME WITH
THE PLACEMENT OF THE BOUNDARY, WHICH COULD PLAY A MAJOR ROLE AS TO
WHETHER OR NOT THE CFWA RECEIVES PRECIP. THE GFS/CANADIAN DRAPE THE
BOUNDARY FROM WEST-TO-EAST ACROSS THE AREA AND ALLOWS FOR SHOWERS
AND POSSIBLE ELEVATED THUNDERSTORMS TO DEVELOP DURING THE DAYTIME
PERIOD SUNDAY. HOWEVER, THE ECMWF AND NAM PUSHES THE BOUNDARY
CLOSER TOWARDS THE I-20 CORRIDOR DURING PEAK HEATING AND KEEPS
BETTER POPS ALONG AND SOUTH OF THE I-85 CORRIDOR. NOT EXPECTING A
SEVERE THREAT FROM THIS, BUT IF ELEVATED INSTABILITY REACHES ITS
PEAK DURING THE AFTERNOON, WOULDN'T BE SURPRISED IF A STORM OR
TWO PRODUCES SMALL HAIL, WITH AN ISOLATED INSTANCE OF 0.50"-1.00"
SIZED HAIL ON STORMS THAT DEVELOP ON THE SOUTH-END OF THE BOUNDARY,
WHERE LOW-LEVEL CONVERGENCE AND INSTABILITY MAXIMIZES WITH COOLER
AIR ALOFT, LOWERING FREEZING LEVELS (~10,000'). AFTERNOON HIGHS
FOR SUNDAY WILL BE RATHER CLOSE TO SATURDAY WITH VALUES AT OR A
FEW TICKS BELOW NORMAL. WITH THE LOSS OF PEAK HEATING AND WEAK
SURFACE HIGH MOVING OVER THE OH/TN VALLEYS, PUSHING THE BOUNDARY
FURTHER SOUTH WILL HELP TO DRY OUT THE CFWA SUNDAY NIGHT. SOME FORM
OF CONVECTIVE DEBRIS MAY ROAM OVERHEAD SUNDAY NIGHT, ESPECIALLY IN
THE SOUTHERN HALF OF THE CFWA LEADING TO OVERNIGHT LOWS REMAINING A
CATEGORY OR SO BELOW NORMAL AS THE SURFACE HIGH SHOULD TAKE CONTROL
OF THE SENSIBLE WEATHER BY DAYBREAK MONDAY WITH LESS CLOUD COVER.
LONG TERM /MONDAY THROUGH THURSDAY/
AS OF 300 AM EDT FRIDAY: BROAD CYCLONIC FLOW GRADUALLY BREAKDOWNS
DOWN MONDAY INTO TUESDAY AS LONGWAVE UPPER RIDGING BUILDS IN
FROM THE WEST. SYNOPTICALLY, THE AREA OF HIGH PRESSURE WILL
SHIFT EASTWARD IN RESPONSE AND SLIP OFFSHORE. GUIDANCE DIFFER
IN HOW THIS IS HANDLED AS THE DETERMINISTIC GFS DEEPENS IT INTO
A BERMUDA HIGH AS A MID-LEVEL ANTICYCLONE DEVELOP OFFSHORE THE
CAROLINA COAST. THE ECMWF DEVELOPS A CUTOFF LOW IN THE VICINITY
OF THE MID-ATLANTIC COAST BY THE MIDDLE PART OF NEXT WEEK,
WHILE PUSHING THE SURFACE HIGH FURTHER OFFSHORE OVER THE WESTERN
ATLANTIC. GEFS/EPS ARE SOMEWHERE IN BETWEEN WITH PLACING THE UPPER
RIDGE OVER THE EASTERN-THIRD OF THE CONUS AND SHOWING THE HIGH
MOVING IN THE VICINITY OF BERMUDA. EITHER WAY, WARMER THICKNESSES
WILL RETURN TO GO ALONG WITH AN UPTICK IN BETTER MOISTURE TRANSPORT,
LEADING TO WARMER AND MORE HUMID CONDITIONS BY TUESDAY AND BEYOND,
WITH AFTERNOON HIGHS AND OVERNIGHT LOWS LIKELY TO EXCEED NORMAL
VALUES BY AT LEAST A FEW DEGREES. THERE IS SOME FORM OF CONSENSUS
AMONGST MODEL GUIDANCE OF SENDING IN A COLD FRONT FROM THE WEST
LATER WEDNESDAY INTO THURSDAY, WHILE THE UPPER RIDGE BREAKS DOWN
AND THE LOW-LEVEL RETURN FLOW INCREASES. WITHOUT MUCH SYNOPTIC
SUPPORT AND A WARM AND MOIST AIRMASS IN PLACE, GUIDANCE STRUGGLE
TO COMPLETE A FULL FROPA THROUGH THE FORECAST PERIOD AND THERE
ARE SOME SIGNS THAT THE BOUNDARY COULD STALL. IN THIS CASE, DAILY
SHOWERS AND THUNDERSTORMS LOOK TO MAKE A RETURN TO THE FORECAST BY
THURSDAY OF NEXT WEEK AND MAY LINGER INTO THE UPCOMING WEEKEND AS
THE FLOW ALOFT FLATTENS OUT AND THE BOUNDARY BECOMES MORE PARALLEL
TO THE MEAN FLOW.
AVIATION /12Z FRIDAY THROUGH TUESDAY/
AT KCLT AND ELSEWHERE: CIGS STARTING OUT THIS MORNING IN THE IFR TO
LIFR RANGE WITH ONLY PATCHY VSBY RESTRICTIONS. CIGS WILL LIFT TO MVFR
BY MID-MORNING AND VFR BY NOON. A LINE OF THUNDERSTORMS AHEAD OF A
COLD FRONT MOVES INTO THE MOUNTAINS NEAR NOON AND SPREADS SE ACROSS
THE AREA THROUGH THE AFTERNOON. HAVE TEMPOS IN PLACE FOR THIS. A
SECONDARY LINE OF CONVECTION ALONG THE FRONT MAY MOVE ACROSS KCLT.
HAVE A PROB30 FOR THIS. GUSTY SW WINDS PICK UP AHEAD OF THE STORMS
TURNING MORE WESTERLY BEHIND. SKIES CLEAR BEHIND THE STORMS WITH
WINDS TAPERING OFF THROUGH THE EVENING.
OUTLOOK: SHOWERS AND A FEW THUNDERSTORMS POSSIBLE AGAIN SATURDAY AND
SUNDAY. DRY HIGH PRESSURE AND VFR CONDITIONS MONDAY AND TUESDAY.
GSP WATCHES/WARNINGS/ADVISORIES
GA...NONE.
NC...NONE.
SC...NONE.
SYNOPSIS...CAC
NEAR TERM...RWH
SHORT TERM...CAC
LONG TERM...CAC
AVIATION...RWH
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