010
FXUS62 KGSP 301049
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
649 AM EDT THU JUL 30 2026
WHAT HAS CHANGED
UPDATED TEMPS AND DEWPOINTS THIS MORNING PER LATEST OBS, AND
ACCOUNTED FOR MORE VALLEY FOG THAN ORIGINALLY EXPECTED. AVIATION
DISCUSSION REVISED FOR 12Z TAFS.
KEY MESSAGES
1. NEAR-NORMAL TEMPERATURES WITH RELATIVELY LOW HUMIDITY THROUGH
FRIDAY, AND A NEAR-ZERO CHANCE OF RAIN.
2. ANOTHER FRONTAL SYSTEM IS EXPECTED TO ARRIVE FROM THE WEST
THIS WEEKEND, POSSIBLY STALLING ACROSS OUR AREA EARLY NEXT WEEK,
BRINGING BACK HIGH RAIN CHANCES BUT ALSO BELOW-NORMAL TEMPERATURES.
DISCUSSION
KEY MESSAGE 1: NEAR-NORMAL TEMPERATURES WITH RELATIVELY LOW HUMIDITY
THROUGH FRIDAY, AND A NEAR-ZERO CHANCE OF RAIN.
SFC HIGH PRESSURE SOUTH OF THE GREAT LAKES WILL MAINTAIN LIGHT
NORTHERLY BREEZES OVER MOST OF THE AREA THROUGH TODAY; FRONT WILL
REMAIN STALLED OVER THE SC LOWCOUNTRY AND SOUTH GA. UNDER CLEAR
SKIES SOME FOG FORMED IN THE MOUNTAIN VALLEYS AND A COUPLE OF RURAL
RIVERSIDE LOCATIONS IN THE PIEDMONT, BUT THESE SHOULD DISSIPATE
QUICKLY THIS MORNING WITH FULL SUNSHINE. TEMPERATURES TODAY WILL
RUN A COUPLE DEGREES BELOW NORMAL, AND VERY DRY AIR SHOULD MIX DOWN
FROM THE TOP OF THE PBL SUCH THAT DEWPOINTS FALL WELL INTO THE 50S
AT MANY LOCATIONS DURING MID TO LATE AFTERNOON. RH WILL REACH THE
MID TO UPPER 30% RANGE, WITH A FEW LOCALIZED AREAS CLOSER TO 30%
LIKELY. AS THE PREVIOUS SHIFT SAID, "AAAHHH." THE HIGH WILL SHIFT
OVER THE APPALACHIANS TONIGHT AND WINDS SHOULD TREND LIGHTER; UNDER
MOSTLY CLEAR SKIES AND WITH DEWPOINTS NOT REALLY REBOUNDING MUCH, IT
APPEARS REASONABLE TO FAVOR THE COOLER END OF THE GUIDANCE RANGE FOR
FRI MORNING MINS, SO OUR FORECAST ENDS UP 5-8 DEGREES BELOW NORMAL.
WEAK RETURN FLOW SHOULD DEVELOP IN LOW LEVELS DURING THE DAY
FRIDAY AS THE HIGH SHIFTS TO OUR EAST, PROMOTING SOME DEGREE OF
MOISTURE RETURN, BUT THAT WILL BE OFFSET BY GOOD MIXING INTO STILL
DRY AIR ABOVE THE PBL, AND WITH TEMPERATURES TRENDING SLIGHTLY
WARMER WE END UP WITH SIMILAR MIN RH IN THE AFTERNOON. A SHALLOW
LAYER OF INSTABILITY COULD DEVELOP BELOW THE SUBSIDENCE INVERSION,
SO WE SHOULD SEE AN UPTICK IN DIURNAL CUMULUS THOUGH NOT ENOUGH
TO SUGGEST A RETURN OF MORE THAN SINGLE-DIGIT POPS.
KEY MESSAGE 2: ANOTHER FRONTAL SYSTEM IS EXPECTED TO ARRIVE FROM
THE WEST THIS WEEKEND, POSSIBLY STALLING ACROSS OUR AREA EARLY
NEXT WEEK, BRINGING BACK HIGH RAIN CHANCES BUT ALSO BELOW-NORMAL
TEMPERATURES.
HIGH PRESSURE WILL BE OFFSHORE BY LATE FRIDAY. SOUTHWESTERLY LOW
LEVEL FLOW WILL CONTINUE FRIDAY EVENING, BY WHICH TIME A MATURING
LOW PRESSURE SYSTEM WILL BE PRESENT IN THE UPPER MISSISSIPPI
VALLEY. THIS SYSTEM WILL REMAIN ON A SOUTHEASTWARD TRACK AS
IT BEGINS TO OCCLUDE EARLY SATURDAY MORNING. THE NEAR-SFC FLOW
APPEARS TO BACK SLIGHTLY IN ADVANCE OF THE SYSTEM, WHICH SHOULD
INCREASE MOISTURE TRANSPORT FROM THE ATLANTIC AND DEVELOP CLOUD
COVER DURING THE MORNING. THE FORWARD PROGRESS OF THE SYSTEM SLOWS
AS IT CONTINUES TO OCCLUDE BUT WAA STRENGTHENS ALOFT AND PWATS
MARCH UPWARD THROUGH SATURDAY. VERTICAL PROFILES AGAIN APPEAR AT
LEAST MARGINALLY FAVORABLE FOR DEEP CONVECTION AND POPS INCREASE
STEADILY FROM WEST TO EAST, ALONG WITH ISOLATED TO SCATTERED
THUNDERSTORMS. ASSUMING CLOUD COVER FORMS AS EXPECTED TEMPERATURES
SHOULD REMAIN SIMILAR TO FRIDAY'S ALTHOUGH RH VALUES WILL BE BACK
TO AROUND NORMAL, SO IT WILL BE ON THE MUGGY SIDE.
THE SHORTWAVE APPEARS TO PHASE WITH A BROADER WAVE MOVING ACROSS
THE GREAT LAKES LATE SATURDAY OR SUNDAY, AND THE COMBINED
TROUGH PROMOTES MOIST FLOW FURTHER UP THE EASTERN SEABOARD,
WASHING OUT THE LAST VESTIGES OF THE DRY AIRMASS AND BRINGING
BACK SUBTROPICAL DEWPOINTS AND PWATS SUNDAY, AND THE BEST OVERALL
CHANCE OF PRECIP APPEARS THEN. CLOUDS AND PRECIP HINDER WARMING
SUCH THAT TEMPERATURES END UP 6-9 BELOW NORMAL. THE HIGH PWAT,
DEEP WARM CLOUD LAYER, AND SMALL MBE VECTORS IMPLY A THREAT OF AT
LEAST LOCALLY HEAVY RAINFALL. MODELS STILL MOSTLY SHOW AN UPPER
LOW BEING LEFT BEHIND AS THE NORTHERN TROUGH REMAINS PROGRESSIVE,
AND A CONVERGENCE ZONE STRETCHING OUT BETWEEN THE LOWER MS VALLEY
AND THE NORTHEAST STATES. THERE REMAINS SPREAD AS TO THE POSITION
AND HOW LONG THIS LINGERS OVER OUR REGION BUT IT APPEARS LIKELY
TO LAST THROUGH TUESDAY IF NOT WEDNESDAY. HENCE POPS REMAIN
ABOVE CLIMATOLOGY EACH DAY AND OVERNIGHT PRECIP CANNOT BE RULED
OUT. TEMPERATURES REMAIN BELOW NORMAL BUT TREND GRADUALLY UPWARD
EACH DAY MON-WED.
AVIATION /12Z THURSDAY THROUGH MONDAY/
AT KCLT AND ELSEWHERE: DRY AND VFR THRU THE PERIOD ASIDE FROM SOME
MOUNTAIN VALLEY FOG/STRATUS IN THE FIRST HR OR TWO OF THE PERIOD,
THOUGH THE FOG IS NOT EXPECTED TO SPREAD TO KAVL. GIVEN THE DRY
CONDITIONS DIURNAL CUMULUS TODAY WILL BE RATHER SPARSE. WINDS MAINLY
NNW TO NE THRU THE PERIOD, POSSIBLY BACKING TO SW AT KAND DURING THE
AFTERNOON. ENOUGH GUSTS ARE EXPECTED TO OCCUR AT KAVL TO WARRANT
A MENTION; A BRIEF GUST OR TWO IS POSSIBLE ELSEWHERE. MOUNTAIN
VALLEY FOG LIKELY AGAIN TONIGHT NEAR THE TN BORDER BUT CONFIDENCE
TOO LOW TO INCLUDE AT KAVL. WINDS WILL COME UP FROM THE SW LATE FRI
MORNING AT KCLT, AND DIURNAL CU POTENTIALLY WILL BE A LITTLE LOWER
(STILL VFR) AND MORE NUMEROUS AS MOISTURE BEGINS TO THE AREA.
OUTLOOK: DRY AND VFR THROUGH FRIDAY, WITH SHOWER AND THUNDERSTORM
CHANCES AND ASSOCIATED RESTRICTIONS RETURNING THIS WEEKEND INTO
EARLY NEXT WEEK. LOW STRATUS AND/OR FOG WILL BE POSSIBLE EACH
MORNING STARTING FRIDAY, MAINLY IN THE MTN VALLEYS.
GSP WATCHES/WARNINGS/ADVISORIES
GA...NONE.
NC...NONE.
SC...NONE.
JCW
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