155
FXUS62 KGSP 261832
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
232 PM EDT SUN OCT 26 2025
SYNOPSIS
A COLD AIR WEDGE PATTERN WILL SET UP OVER THE WESTERN CAROLINAS
TONIGHT INTO EARLY NEXT WEEK BRINGING MUCH NEEDED RAINFALL AND
COLDER TEMPERATURES. ANOTHER LOW PRESSURE SYSTEM WILL IMPACT OUR
AREA DURING THE MIDDLE OF NEXT WEEK. CONDITIONS GRADUALLY DRY OUT BY
LATE NEXT WEEK WITH TEMPERATURES REMAINING BELOW NORMAL.
NEAR TERM /THROUGH MONDAY/
AS OF 115 PM SUNDAY: COOL SFC RIDGING WILL REMAIN WEDGED INTO THE
REGION THROUGH THE PERIOD. WITHIN THE DIFFLUENT FLOW ALOFT
DOWNSTREAM OF THE EASTWARD WOBBLING CLOSED LOW, CLOUDINESS HAS
LOWERED AND THICKENED TODAY ON THE WAY TO BECOMING SOLIDLY OVERCAST
TONIGHT. WITH THE UPPER DIVERGENCE AND DPVA SLUGS, SCATTERED TO
ISOLATED LIGHT SHOWERS HAD BLOSSOMED THIS AFTERNOON, AND WITHIN THE
INCREASINGLY MOIST UPGLIDE FLOW, PCPN WILL BECOME PROGRESSIVELY
WIDESPREAD AS THE NIGHT WEARS ON WITH THE CHANCES FOR EMBEDDED
HEAVIER SHOWERS ESPECIALLY NEAR FAVORED UPSLOPE AREAS OF THE
SOUTHERN CWFA MONDAY MORNING. WIDESPREAD RAIN WITH EMBEDDED HEAVY
SHOWERS WILL OVERSPREAD THE BALANCE OF THE REGION MONDAY MORNING.
PCPN WILL STRENGTHEN ONGOING CAD REGIME, PROMPTING GUSTY NE WINDS
AND LITTLE UPWARD TEMPERATURE MOVEMENT THROUGHOUT THE DAY. HAVE
UNDERCUT THE MAXT GUIDANCE CONSENSUS AND IT REMAINS WITHIN THE REALM
OF POSSIBILITY THAT RECORD LOW MAXT VALUES WILL BE THREATEN (48 OR
BOTH KGSP AND KCLT). DESPITE THE DREARY MONDAY FORECAST, BENEFICIAL
RAINFALL ON THE ORDER OF 1 TO 2 INCHES REMAIN POSSIBLE, WHICH WILL
MAKE A DENT IN OUR 60 DAY DEFICITS.
SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/
AS OF 2 PM EDT SUNDAY: A COMPLEX LARGE-SCALE BLOCKING PATTERN
WILL DOMINATE THE PERIOD, WITH AN EVOLVING HYBRID BLOCK
TRANSITIONING TO A REX BLOCK NORTH OF THE AREA. INITIALLY, A
SPLIT-FLOW REGIME FEATURES AN OMEGA BLOCK ACROSS THE NORTHERN
STREAM, INCLUDING A SHORTWAVE RIDGE FROM ONTARIO AND QUEBEC
SOUTHWARD THROUGH THE GREAT LAKES, A DOWNSTREAM CLOSED LOW OFF
THE MAINE COAST, AND AN UPSTREAM TROUGH OVER THE CENTRAL PLAINS.
IN THE SOUTHERN STREAM, A SHORTWAVE ROUNDING THE BASE OF THE
JET WILL PASS ACROSS THE SOUTHEAST MONDAY NIGHT, ALIGNING
BENEATH THE NORTHERN RIDGE AND BRIEFLY PRODUCING A HIGH-OVER-LOW
CONFIGURATION. BY TUESDAY, THIS SOUTHERN-STREAM WAVE AND THE
NEW ENGLAND UPPER LOW WILL PHASE, FORMING A MATURE REX BLOCK
NORTH OF THE CAROLINAS. A SECONDARY NORTHERN-STREAM TROUGH OVER
THE CENTRAL PLAINS WILL THEN DIG SOUTHEAST AND PHASE WITH THE
NEWLY FORMED LOW BY WEDNESDAY, PRODUCING A DEEP, SLOW-MOVING
UPPER LOW NEAR OR WEST OF THE APPALACHIANS.
AT THE SURFACE, A COLD-AIR DAMMING (CAD) REGIME WILL REMAIN
ENTRENCHED THROUGH MIDWEEK. DETERMINISTIC MODEL GUIDANCE
CONTINUES TO ERODE THE WEDGE TOO QUICKLY, A KNOWN BIAS IN THIS
PATTERN. CONFIDENCE IS HIGH THAT THE WEDGE WILL PERSIST THROUGH
WEDNESDAY, RESULTING IN BELOW-NORMAL TEMPERATURES, LOW CLOUDS,
AND PERIODS OF OVERRUNNING PRECIPITATION. THE FORECAST LEANS ON
PROBABILISTIC TEMPERATURE GUIDANCE FROM THE NBM, BLENDING TOWARD
THE 75TH TO 90TH PERCENTILE FOR NIGHTTIME LOWS (INDICATING
HIGHER CONFIDENCE IN COOLER NIGHTS UNDER THE WEDGE) AND THE 10TH
TO 25TH PERCENTILE FOR DAYTIME HIGHS (REFLECTING HIGH
LIKELIHOOD THAT DAYTIME WARMING WILL BE LIMITED BY THE SHALLOW
COLD LAYER).
WIDESPREAD RAIN IS EXPECTED MONDAY NIGHT AS THE SOUTHERN-STREAM
DISTURBANCE CROSSES THE REGION. THE AREA WILL BE POSITIONED
BETWEEN COUPLED UPPER-JET STREAKS WITH A 50 KT EAST-
NORTHEASTERLY LOW-LEVEL JET ENHANCING OROGRAPHIC ASCENT ALONG
THE BLUE RIDGE. ENSEMBLE QPF GUIDANCE SUPPORTS A HIGH
PROBABILITY (AROUND AN 80-TO-90 PERCENT CHANCE) OF MEASURABLE
RAIN ACROSS THE ENTIRE CWA, WITH MOST DETERMINISTIC MEMBERS
CLUSTERING AROUND ONE-THIRD TO ONE INCH OF RAINFALL. A FEW HIGH-
RESOLUTION MEMBERS SHOW CONVECTIVE ENHANCEMENT, CONSISTENT WITH
WEAK ELEVATED INSTABILITY (MUCAPE NEAR 100 J/KG AND MID-LEVEL
DRYING). SHOULD THIS INSTABILITY MATERIALIZE, LOCALIZED RAINFALL
MAXIMA OF 1.5 TO 3 INCHES CANNOT BE RULED OUT ACROSS THE NC
FOOTHILLS AND WESTERN PIEDMONT BASED ON THE 90TH AND 95TH
PERCENTILE FROM THE HREF AND REFS CAM ENSEMBLES.
A BRIEF LULL IN PRECIPITATION IS EXPECTED TUESDAY THROUGH EARLY
WEDNESDAY AS THE REGION LIES BETWEEN SYSTEMS. ENSEMBLE
PROBABILITY DISTRIBUTIONS SUGGEST A 40-TO-60 PERCENT CHANCE OF
LIGHT RAIN OR DRIZZLE CONTINUING UNDER THE PERSISTENT CAD WEDGE.
EVEN DURING ANY LULL, LOW CLOUDS AND DAMP CONDITIONS WILL
LIKELY PERSIST.
RAIN COVERAGE WILL INCREASE AGAIN WEDNESDAY AFTERNOON AND
EVENING AS THE NEXT PHASING UPPER LOW APPROACHES FROM THE WEST.
PROBABILISTIC GUIDANCE SHOWS A 70-TO-90 PERCENT CHANCE OF
MEASURABLE RAIN ACROSS MOST OF THE CWA, WITH THE HIGHEST
PROBABILITIES FOCUSED ALONG THE BLUE RIDGE WHERE SOUTHEAST
850-MB FLOW ENHANCES LIFT. ALTHOUGH DETERMINISTIC GUIDANCE
DEPICTS WARM-FRONTAL EROSION, ENSEMBLE SPREAD REMAINS LARGE, AND
THE MEDIAN SCENARIO KEEPS THE SURFACE WEDGE INTACT ACROSS MUCH
OF THE PIEDMONT. STRONG DYNAMICS AND ELEVATED INSTABILITY MAY
LEAD TO ANOTHER ROUND OF MODERATE RAINFALL WEDNESDAY NIGHT, WITH
ENSEMBLE QPF AVERAGES OF ONE-HALF TO ONE INCH.
LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/
AS OF 2 PM EDT SUNDAY: BY WEDNESDAY NIGHT INTO THURSDAY, THE
DEEP UPPER LOW OVER THE OHIO AND TENNESSEE VALLEYS WILL INTERACT
WITH A DEVELOPING SECONDARY SURFACE LOW NEAR OR EAST OF THE
SOUTHERN APPALACHIANS. WHILE GLOBAL ENSEMBLE MEANS HAVE COME
INTO BETTER ALIGNMENT ON THE GENERAL EVOLUTION, TIMING
DIFFERENCES PERSIST AMONG MEMBERS REGARDING THE TRANSITION
BETWEEN THE PRIMARY AND SECONDARY LOWS. PROBABILISTIC TIMING
SPREADS RANGE FROM LATE WEDNESDAY NIGHT TO THURSDAY AFTERNOON
FOR THE FRONTAL PASSAGE ACROSS THE PIEDMONT. THIS TRANSLATES TO
A 50-TO-70 PERCENT CHANCE THAT MODERATE RAINFALL CONTINUES INTO
EARLY THURSDAY BEFORE DRYING FROM THE WEST AS THE MID-LEVEL DRY
SLOT ARRIVES.
AS THE UPPER LOW LIFTS NORTHEAST THURSDAY, ENSEMBLE GUIDANCE
SUPPORTS A 70-TO-90 PERCENT CHANCE OF RAIN ENDING ACROSS THE
PIEDMONT, WHILE THE NC MOUNTAINS MAY MAINTAIN A 60-TO-80 PERCENT
CHANCE OF LINGERING LIGHT PRECIPITATION DUE TO UPSLOPE FLOW.
FRIDAY WILL FEATURE POST-FRONTAL COLD ADVECTION AND WESTERLY
WINDS. ENSEMBLE TEMPERATURE SPREADS OF 7 TO 10 DEGREES SUGGEST
BELOW-NORMAL CONDITIONS WITH HIGHS 10 TO 15 DEGREES BELOW NORMAL
IN THE MOUNTAINS AND 5 TO 10 DEGREES BELOW ELSEWHERE. THE
PROBABILITY OF DRY CONDITIONS FRIDAY AFTERNOON AND EVENING
EXCEEDS 80 PERCENT, OFFERING IMPROVING CONDITIONS FOR OUTDOOR
ACTIVITIES.
THROUGH THE WEEKEND, BROAD UPPER TROUGHING WILL PERSIST OVER THE
EASTERN UNITED STATES. ENSEMBLE MEANS INDICATE HIGH CONFIDENCE
(AROUND 70-TO-90 PERCENT PROBABILITY) OF CONTINUED DRY WEATHER
THROUGH SATURDAY, FOLLOWED BY INCREASING UNCERTAINTY BY SUNDAY
AS THE NEXT SYSTEM APPROACHES FROM THE WEST. TIMING SPREADS
EXCEED 24 HOURS AMONG ENSEMBLE MEMBERS, WITH ROUGHLY A 40
PERCENT PROBABILITY OF OVERRUNNING PRECIPITATION REACHING THE
AREA BY LATE SUNDAY. TEMPERATURES WILL GRADUALLY MODERATE BUT
REMAIN SEVERAL DEGREES BELOW NORMAL THROUGH THE WEEKEND.
AVIATION /18Z SUNDAY THROUGH FRIDAY/
AT KCLT AND ELSEWHERE: IT REMAINS PROBABLE THAT VFR CONDITIONS WILL
HANG ON INTO THIS EVENING WITH THE SENSIBLE WX FEATURING WIDESPREAD
VFR LVL STRATOCU CIGS AND SCATTERED/SPOTTY LIGHT SHOWERS. WITH
PROGRESSIVE MOISTENING AND THE APPROACH OF LARGER SCALE FORCING
TONIGHT, FLIGHT CONDITIONS WILL DETERIORATE, AS SHOWER CHANCES RAMP
UP AND CIGS WILL HAVE THE POTENTIAL TO BECOME MVFR BEFORE DAYBREAK.
A DREARY, RAINY, BLUSTERY AND CHILLY DAY IS ON TAP FOR MONDAY
FEATURING POCKETS OF IFR CONDITIONS AND GUSTY NE WINDS.
OUTLOOK: WIDESPREAD PRECIP AND RESTRICTIONS LINGERING THROUGH
DAYBREAK TUESDAY. CONFIDENCE IS LOW HOW MUCH IMPROVEMENT IN
CONDITIONS WILL OCCUR TUESDAY, BUT PERIODIC PRECIP/RESTRICTIONS
PROBABLY RETURN IN SOME FASHION FOR WED AND THU. DRIER WEATHER
RETURNS TO END THE WEEK.
GSP WATCHES/WARNINGS/ADVISORIES
GA...NONE.
NC...NONE.
SC...NONE.
SYNOPSIS...CSH
NEAR TERM...CSH
SHORT TERM...JRK
LONG TERM...JRK
AVIATION...CSH
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