671
FXUS62 KCAE 181812
AFDCAE
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE COLUMBIA SC
212 PM EDT SAT JUL 18 2026
WHAT HAS CHANGED
HEAT ADVISORY ISSUED ALONG AND SOUTH OF THE I-20 CORRIDOR
TODAY. CONVECTIVE COVERAGE WILL INCREASE BY LATE AFTERNOON.
AVIATION DISCUSSION UPDATED FOR 18Z TAFS.
KEY MESSAGES
- 1. HEAT ADVISORY IN EFFECT FROM 12 PM TO 8 PM ALONG AND SOUTH
OF THE I-20 CORRIDOR AS HEAT INDICES REACH BETWEEN 105-108F.
ISOLATED TO SCATTERED CONVECTION EXPECTED WITH A COUPLE STRONG
TO SEVERE STORMS POSSIBLE THIS AFTERNOON/EVENING.
- 2. MORE THUNDERSTORM CHANCES SUNDAY INTO MONDAY WITH POSSIBLE
SEVERE THUNDERSTORMS. ANOTHER CHANCE FOR STRONG CONVECTION
POSSIBLE DURING THE MIDWEEK.
DISCUSSION
KEY MESSAGE 1: HEAT ADVISORY IN EFFECT FROM 12 PM TO 8 PM ALONG
AND SOUTH OF THE I-20 CORRIDOR AS HEAT INDICES REACH BETWEEN
105-108F. ISOLATED TO SCATTERED CONVECTION EXPECTED WITH A
COUPLE STRONG TO SEVERE STORMS POSSIBLE THIS AFTERNOON/EVENING.
NOT MUCH CHANGE OVERALL IN THE FORECAST FOR BOTH HEAT AND
CONVECTIVE ACTIVITY THIS AFTERNOON. OBSERVATIONS FOR BOTH TEMPS
AND DEW POINTS ARE ON TRACK FOR THE FORECAST TODAY WITH HEAT
INDICES EXPECTED TO PUSH BETWEEN 105-110F ALONG AND SOUTH OF
I-20. DESPITE THE HIGH TEMPS AND DEW POINTS, MID-LEVEL CAPPING
IS STILL IN CONTROL IN THE MIDLANDS WITH GENERALLY FLAT CU AND A
LACK OF ANY VERTICAL DEVELOPMENT YET. CONVECTIVE COVERAGE THIS
AFTERNOON/EVENING SHOULD TREND A BIT SIMILAR TO THAT SEEN
YESTERDAY. THIS LINGERING MID-LEVEL CAPPING SHOULD HOLD ON INTO
THE MID-AFTERNOON BEFORE A COMBINATION OF INCREASED SURFACE
TROUGHING AND THE SEA BREEZE INITIATE DEEPER CONVECTION LATE IN
THE AFTERNOON AND INTO THE EVENING HOURS. UPPER SUPPORT REMAINS
VERY MEAGER WITH EFFECTIVE SHEAR VALUES UNDER 10 KTS, BUT STRONG
INSTABILITY IS STILL PROGGED TO DEVELOP (SBCAPE NEAR 3000 J/KG)
IN THIS VERY MOIST ENVIRONMENT. A COUPLE STRONG TO SEVERE
STORMS WILL BE POSSIBLE AS ROBUST DCAPE VALUES BETWEEN 1000-1300
J/KG, 3KM CAPE NEAR 100 J/KG, AND TEI VALUES BETWEEN 25-30
BRING AN INCREASED RISK FOR STRONG DOWNBURSTS AND THE ASSOCIATED
DAMAGING WIND RISK. DUE TO THIS, PORTIONS OF THE FA ARE IN
SPC'S MARGINAL RISK (LEVEL 1 OUT OF 5) FOR SEVERE WEATHER TODAY
WITH A NORTHERN SLIVER IN A SLIGHT RISK (2 OUT OF 5).
KEY MESSAGE 2: MORE THUNDERSTORM CHANCES SUNDAY INTO MONDAY
WITH POSSIBLE SEVERE THUNDERSTORMS. ANOTHER CHANCE FOR STRONG
CONVECTION POSSIBLE DURING THE MIDWEEK.
AS HAS BEEN DISCUSSED, A DEEPENING SHORTWAVE IS PROGGED TO MOVE
INTO THE MID-ATLANTIC THROUGH THE DAY SUNDAY, DRAGGING A
SURFACE FRONT THAT COULD NEAR THE PEE DEE SUNDAY NIGHT. ENHANCED
MOISTURE ADVECTION IS SHOWN ACROSS GUIDANCE AHEAD OF THESE
FEATURES WITH PWAT'S REACHING ABOVE 2", PARTLY THANKS TO GULF
MOISTURE BEING TRANSPORTED NORTHWARD ON THE EASTERN PERIPHERY OF
A DEVELOPING WEAK TROPICAL DISTURBANCE IN THE NORTHEASTERN
GULF. OVERALL, THE ENVIRONMENT IS NOT EXPECTED TO BE ALL THAT
DIFFERENT FROM THE LAST COUPLE OF DAYS, FAVORING A DAMAGING WIND
RISK FROM PRECIP-LOADED DOWNDRAFTS. THE MAIN DIFFERENCE IS
MARGINAL UPPER SUPPORT SHOULD BRING INCREASED COVERAGE AND
EFFECTIVE SHEAR VALUES NEAR 10-15 KTS, ESPECIALLY TOWARD THE PEE
DEE, WHICH COULD AID IN BETTER ORGANIZATION OF A FEW CLUSTERS.
THIS HAS RESULTED IN MOST OF THE FA REMAINING IN A MARGINAL RISK
FOR SEVERE WEATHER, BUT A SLIGHT RISK (LEVEL 2 OUT OF 5) STILL
SCRAPES THE PEE DEE WITH THE GREATER SHEAR HERE. THE FRONTAL
BOUNDARY IS EXPECTED TO REMAIN NEAR THE PEE DEE INTO MONDAY WITH
WEAK SHORTWAVE ENERGY PASSING THROUGH THE REGION, BRINGING
ANOTHER DAY WITH INCREASED AFTERNOON CONVECTIVE COVERAGE AND THE
CHANCE FOR A COUPLE STRONG TO MARGINALLY SEVERE STORMS.
NHC NOW HAS A 40% OUTLOOK AREA AS THE EC ENSEMBLE AND GOOGLE
DEEPMIND HAVE TRENDED MORE TOWARDS THE WEAK TROPICAL DISTURBANCE
MEANDERING THROUGH THE NORTHEASTERN GULF EARLY IN THE WEEK
BEFORE SLOWLY DRIFTING WESTWARD INTO THE MID WEEK. THIS SHOULD
STILL ALLOW DEEP MOISTURE TO ADVECT INTO THE REGION FROM THE
SOUTH, BUT BOTH ENSEMBLE AND DETERMINISTIC GUIDANCE HAVE
DISPLAYED INCREASED CONFIDENCE THAT AN EVEN SHARPER SHORTWAVE
SHOULD DIG INTO THE EASTERN CONUS DURING THE MID-WEEK, POSSIBLY
DRAGGING ANOTHER FRONTAL BOUNDARY NEAR THE FA. ENHANCED
KINEMATICS COUPLED WITH SEASONABLE TO STRONG INSTABILITY COULD
BRING ANOTHER CHANCE FOR STRONGER CONVECTION DURING THE MIDWEEK
AS HIGHLIGHTED IN CSU/CIPS/NCAR MACHINE LEARNING AND AI
GUIDANCE. TIMING DIFFERENCE STILL NEED TO BE SORTED OUT ACROSS
DETERMINISTIC GUIDANCE, BUT THE PATTERN SEEMS FAVORABLE FOR
POTENTIAL SEVERE WEATHER AGAIN.
AVIATION /18Z SATURDAY THROUGH THURSDAY/
VFR CONDITIONS ARE EXPECTED TO PREVAIL FOR THE FORECAST PERIOD,
ALTHOUGH BRIEF RESTRICTIONS ARE POSSIBLE ASSOCIATED WITH
AFTERNOON/EVENING THUNDERSTORMS.
DIURNAL CUMULUS FIELD CONTINUES TO EXPAND ACROSS THE AREA THIS
AFTERNOON, AND ANY CEILINGS SHOULD QUICKLY IMPROVE TO VFR
LEVELS. SCATTERED CONVECTION SHOULD INITIATE ALONG A BOUNDARY
TO THE NORTH AND DROP INTO THE AREA LATER THIS AFTERNOON, AND
ALONG THE INLAND PROGRESSING SEA BREEZE. THE TAFS INCLUDE A
PROB30 GROUP FROM 20-01Z TO ACCOUNT FOR THE THUNDERSTORM
POTENTIAL. WINDS WILL GENERALLY BE FROM THE SOUTHWEST AT 6-10 KT
INTO THIS EVENING, THEN SUBSIDE A BIT OVERNIGHT.
EXTENDED AVIATION OUTLOOK...POTENTIAL FOR RESTRICTIONS FROM SHOWERS
AND THUNDERSTORMS CONTINUES INTO NEXT WEEK.
CAE WATCHES/WARNINGS/ADVISORIES
SC...HEAT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR SCZ016-022-
027>031-035-037-038-041-135>137.
GA...HEAT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR GAZ063>065-077.
DISCUSSION...42
AVIATION...JAQ
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