328
FXUS62 KGSP 122319
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
719 PM EDT SAT SEP 12 2026
WHAT HAS CHANGED
RAINFALL CHANCES WERE INCREASED SLIGHTLY FOR MONDAY AFTERNOON.
THE AVIATION DISCUSSION WAS UPDATED FOR THE RECENT 00Z TAF ISSUANCE.
KEY MESSAGES
1. SCATTERED SHOWERS AND SOME EMBEDDED THUNDERSTORMS WILL CONTINUE
THIS AFTERNOON AND EVENING AHEAD OF AN ADVANCING COLD FRONT. THE
FRONT WILL CROSS THE AREA TONIGHT, RESULTING IN QUIETER CONDITIONS
ON SUNDAY AND EARLY MONDAY.
2. A BACKDOOR COLD FRONT SHOULD ARRIVE ON MONDAY AFTERNOON, BUT
CONFIDENCE IS LIMITED ON WHAT, IF ANY, IMPACTS WILL DEVELOP AS
A RESULT.
DISCUSSION
KEY MESSAGE 1: SCATTERED SHOWERS AND SOME EMBEDDED THUNDERSTORMS
WILL CONTINUE THIS AFTERNOON AND EVENING AHEAD OF AN ADVANCING
COLD FRONT. THE FRONT WILL CROSS THE AREA TONIGHT, RESULTING IN
QUIETER CONDITIONS ON SUNDAY AND EARLY MONDAY.
IT'S NOW COMING UP ON 2 PM, AND AS EXPECTED A LOBE OF BETTER
MOISTURE HAS PUSHED INTO THE AREA BENEATH A SHARP Z500 SHORTWAVE
TROUGH ALOFT. WEAK LOW-LEVEL UPGLIDE HAS DEVELOPED IN RESPONSE, AND
SCATTERED SHOWERS WITH RAIN RATES OF 1-2" PER HOUR HAVE DEVELOPED,
MAINLY WEST OF I-26 BUT CONTINUING A NORTHEASTWARD PUSH.
THE 12Z SUITE OF MODEL GUIDANCE IS IN GOOD AGREEMENT THAT THE
SHORTWAVE WILL TRANSLATE EASTWARD THROUGH THIS EVENING AND TONIGHT,
CROSSING THE GSP FORECAST AREA AND MOVING EAST OF I-77 THROUGH
EARLY MORNING SUNDAY. MOST OF THE HI-RES MODELS FEATURE A WEAK
LLJ DEVELOPING AFTER SUNSET, AHEAD OF A WEAK ADVANCING SFC FRONT.
CONFIDENCE IS LIMITED, BUT WITH PWS ALREADY 2-2.2" ACROSS THE
SC ZONES AND PARTS OF THE I-77 CORRIDOR, THIS COULD RESULT IN
INCREASING RAIN RATES AS THE SYSTEM PUSHES ACROSS I-77 AND THE
CHARLOTTE METRO AREA. THIS AREA ISN'T ESPECIALLY PRIMED YET FOR
HYDRO ISSUES, BUT CAN'T ENTIRELY RULE OUT ISOLATED NUISANCE FLOODING
IN SOME OF THE FLASHIER SPOTS ACROSS THOSE ZONES (AND IN FACT, WE
DO ALREADY HAVE AN ADVISORY IN EFFECT FARTHER UPSTREAM, ACROSS THE
WESTERN UPSTATE, FOR THAT SAME AXIS OF MOISTURE!). SEVERE PROSPECTS
APPEAR MUCH SMALLER...WITH LIMITED INSTABILITY, POOR LAPSE RATES,
AND VERY MOIST PROFILES KEEPING STRONGER CONVECTION SUPPRESSED.
NONETHELESS, THERE WILL BE A MEAGER ~20KTS OF DEEP LAYER SHEAR,
PARTICULARLY ACROSS THE I-77 CORRIDOR THIS EVENING, SO A FEW
SEMI-ORGANIZED SEGMENTS, PERHAPS EVEN AN ISOLATED STRONG TO SEVERE
WIND GUST, ISN'T ENTIRELY OUT OF THE QUESTION.
HI-RES ENSEMBLES ARE IN GOOD AGREEMENT THAT A SURFACE FRONT WILL
SLIDE ACROSS THE AREA OVERNIGHT, USHERING IN DRIER AIR ON THE
BACKSIDE AS DEPICTED BY LOW-LEVEL THETA-E FIELDS. AS A CONSEQUENCE,
A POTENTIALLY MURKY NIGHT TONIGHT WILL GIVE WAY TO MUCH NICER
CONDITIONS ON SUNDAY, AS A WEAKLY-CAPPED AIR MASS FILTERS IN AND
MOISTURE RETREATS TO OUR EAST. GENERALLY THINK THE SUNDAY/SUNDAY
NIGHT PERIOD SHOULD BE MOSTLY DRY AND QUIET, NOTWITHSTANDING A
FEW RIDGETOP SHOWERS ACROSS THE BLUE RIDGE ON SUNDAY AFTERNOON.
KEY MESSAGE 2: A BACKDOOR COLD FRONT SHOULD ARRIVE ON MONDAY
AFTERNOON, BUT CONFIDENCE IS LIMITED ON WHAT, IF ANY, IMPACTS WILL
DEVELOP AS A RESULT.
BY MONDAY, A BUILDING UPPER ANTICYCLONE OVER THE SOUTHERN GREAT
PLAINS AND GULF COAST WILL BEGIN TO INTERACT WITH LONGWAVE TROUGHING
OVER EASTERN CANADA AND NEW ENGLAND. A NUMBER OF LONGER-RANGE
ENSEMBLES FEATURES A 500MB SHORTWAVE PIVOTING OUT OF THE OHIO VALLEY
BETWEEN THESE TWO FEATURES, AND AT LEAST CLIPPING OUR NORTHERN
AND EASTERN ZONES MONDAY AFTERNOON AND EVENING. THERE'S DECENT
CONFIDENCE WE'LL SEE SOME SYNOPTIC-SCALE LIFT, ENOUGH TO EXPECT AN
INCREASE IN CLOUD COVER, AND LOW-LEVEL THETA-E FIELDS AGAIN SUGGEST
THAT A WEAK BACKDOOR COLD FRONT WILL PUSH ACROSS THE AREA MONDAY
EVENING, TRAILING BEHIND THE TROUGH. HOWEVER, THE ANTECEDENT AIR
MASS WILL HAVE HAD LITTLE TO RECOVER MOISTURE FOLLOWING TONIGHT'S
FROPA, AND AS A RESULT MOST ENSEMBLE MEMBERS DON'T FEATURE MUCH
RAIN WITH THIS BACKDOOR FRONT.
THE CONVECTIVE ENVIRONMENT WILL ONCE AGAIN BE CONSTRAINED BY POOR
LAPSE RATES, AND LIMITED INSTABILITY (BY SOME MODELS' ACCOUNT,
BARELY HITTING 1000 J/KG). THAT BEING SAID, ENSEMBLE PROFILES DO
AT LEAST FEATURE SOME DRY AIR ALOFT, AND MARGINAL DEEP-LAYER SHEAR
VALUES AHEAD OF THE FRONT, TO THE TUNE OF 20-25KTS, SO A NONZERO
THREAT OF STRONG TO SEVERE WINDS COULD BE IN ORDER, CONDITIONAL
UPON ANY CONVECTION ACTUALLY DEVELOPING...WHICH THE RECENT ROUND
OF GUIDANCE ISN'T ESPECIALLY JAZZED ABOUT.
BEHIND THE FRONT, THERE'S A SIGNAL FOR POSSIBLE COLD-AIR DAMMING,
BUT THE UPPER PATTERN IS DEVOID OF MUCH MOISTURE, SO THIS COULD
HAVE MORE OF AN EFFECT ON MID-WEEK TEMPERATURES THAN ANYTHING ELSE,
WITH LIMITED POTENTIAL FOR RAINFALL THROUGH MID- TO LATE-WEEK.
AVIATION /00Z SUNDAY THROUGH THURSDAY/
AT KCLT AND ELSEWHERE: THE FIRST HALF OF THE TAF PERIOD IS EXPECTED
TO REMAIN BUSY WITH A MYRIAD OF RESTRICTIONS ACROSS THE AREA.
ONGOING SHOWERS AND ISOLATED THUNDERSTORMS WILL CONTINUE TO PLAGUE
MOST TERMINALS WITH ASSOCIATED VISIBILITY AND CEILING RESTRICTIONS,
ESPECIALLY DURING HEAVIER RAINFALL RATES. THEREAFTER, A DECK OF
WIDESPREAD LOW STRATUS IS EXPECTED TO DEVELOP OVERNIGHT WITH
CEILINGS FALLING TO IFR/LIFR. PATCHY FOG ALSO CANNOT BE RULED OUT AT
ANY GIVEN TERMINAL. MOUNTAIN VALLEY FOG/STRATUS WILL ALSO BRING
RESTRICTIONS TO KAVL. FOG SHOULD MIX OUT WITH CEILINGS LIFTING AND
SCATTERING WITHIN SEVERAL HOURS OF SUNRISE. THIS WILL BRING A RETURN
TO VFR THROUGH THE REMAINDER OF THE PERIOD. WINDS WILL BE LIGHT OUT
OF THE SOUTH/SOUTHWEST OR VARIABLE OVERNIGHT WITH A WIND SHIFT TO
OUT OF THE NORTH/NORTHWEST SUNDAY MORNING. A FEW LOW END GUSTS WILL
BE POSSIBLE SUNDAY AFTERNOON AT KAVL.
OUTLOOK: QUIET CONDITIONS ARE EXPECTED TO PERSIST THROUGH EARLY
MONDAY. A SECOND ROUND OF SHOWERS MAY DEVELOP ON MONDAY AFTERNOON
AND EVENING, BUT CONFIDENCE IS LOW, AND COVERAGE MAY ONLY BE
ISOLATED.
GSP WATCHES/WARNINGS/ADVISORIES
GA...NONE.
NC...NONE.
SC...NONE.
MPR/TW
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page