533
FXUS62 KCAE 201906
AFDCAE
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE COLUMBIA SC
306 PM EDT THU AUG 20 2026
WHAT HAS CHANGED
RISK FOR A STRONG STORM OR TWO TODAY HAS INCREASED. FORECAST
REMAINS ON TRACK FOR WIDESPREAD CONVECTION FRIDAY WITH FLASH
FLOODING AND DAMAGING WINDS POSSIBLE. AVIATION DISCUSSION
UPDATED FOR 18Z TAF.
KEY MESSAGES
- 1. SEVERE WEATHER AND FLASH FLOODING POSSIBLE FRIDAY.
- 2. A COUPLE STRONG TO SEVERE STORMS POSSIBLE THIS AFTERNOON.
DISCUSSION
KEY MESSAGE 1: SEVERE WEATHER AND FLASH FLOODING POSSIBLE
FRIDAY.
THE FORECAST FOR FRIDAY LARGELY REMAINS ON TRACK AS TROUGHING
OVER THE EASTERN CONUS STRENGTHENS WITH ANOTHER SHORTWAVE
GRADUALLY WORKING TOWARD THE REGION. ALONG WITH THIS UPPER
SUPPORT, A SURFACE FRONT IS ALSO EXPECTED TO SHIFT INTO THE
REGION THROUGH THE DAY. ROBUST HEATING IS EXPECTED THROUGH THE
MORNING INTO THE AFTERNOON WITH SURFACE DEWPOINTS IN THE LOW TO
MID 70S. THIS SHOULD QUICKLY BRING MLCAPE VALUES NEAR 2500-3000
J/KG WITH STEEP LOW LEVEL LAPSE RATES BRINGING DCAPE VALUES NEAR
800-1000 J/KG. ENHANCED KINEMATICS WITH SURGING PWAT'S TO NEAR
2" WILL BRING THE RISK FOR WET MICROBURSTS IN CONVECTION DURING
THE EARLY AFTERNOON. WHILE DAMAGING WIND GUSTS ARE THE PRIMARY
THREAT, CANNOT RULE OUT SOME HAIL AS FAIRLY THICK CAPE PROFILES
ARE SEEN IN THE HAIL GROWTH ZONE. THIS IS FURTHER SUPPORTED IN
ANALOG SOUNDINGS WITH MULTIPLE ANALOGS FOR NEAR SEVERE HAIL WHEN
PULLING FORECAST SOUNDINGS FROM THE RAP/HRRR/RRFS. 12Z GUIDANCE
INDICATES CONVECTION COULD GET GOING AS EARLY AS 16- 19Z,
QUICKLY EXPANDING IN COVERAGE THROUGH THE AFTERNOON AND INTO THE
EARLY EVENING.
THE OVERALL STORM MOTION IS EXPECTED TO BE FAIRLY SLOW (UNDER
20 KTS) AND THE ENVIRONMENT APPEARS PRIMED FOR HEAVY RAINFALL
WITH DEEP WARM CLOUD DEPTHS, NEARLY BOUNDARY PARALLEL DEEP LAYER
SHEAR VECTORS, AND PWAT'S NEAR 2". THE RECENT REFS AND HREF PMM
QPF AMOUNTS SHOW SPOTS OF 2-4" NEAR PORTIONS OF THE PEE DEE AND
NORTHERN MIDLANDS, WHICH IS REASONABLE, BUT BOTH OF THESE
ENSEMBLES ARE KEYING IN ON AMOUNTS NEAR 3-6" JUST ACROSS THE
CWA BORDER IN SOUTHERN NC. ANY SOUTHERN SHIFT IN FORCING/ THIS
AXIS OF HIGHER QPF COULD BRING THE HIGHER AMOUNTS IN THE PEE DEE
AND NORTHERN FA. OVERALL, SOME UNCERTAINTY REMAINS IN THE EXACT
PLACEMENT OF THE HEAVIEST RAINFALL, BUT ISOLATED TO SCATTERED
INSTANCES OF FLASH FLOODING WILL BE POSSIBLE MAINLY ALONG AND
EAST OF THE I-26 CORRIDOR.
KEY MESSAGE 2: A COUPLE STRONG TO SEVERE STORMS POSSIBLE THIS
AFTERNOON.
CONVECTION IS ALREADY FIRING THIS AFTERNOON, LIKELY IN REACTION
TO A CONVECTIVELY ENHANCED SHORTWAVE MOVING INTO THE REGION
FROM THE APPALACHIANS. EARLIER THIS MORNING CONVECTION IN
SOUTHERN TENNESSEE PRODUCED AN UNDULAR BORE/GRAVITY WAVES THAT
WERE SAMPLED BY THE KFFC/KHTX RADAR AND ON SATELLITE IMAGERY. IT
IS LESS EVIDENT NOW, BUT THESE WAVES MAY BE PERSISTING AS THE
SHORTWAVE MOVES OVERHEAD. WITH A STRONGLY UNSTABLE ENVIRONMENT
(SBCAPE OVER 3000 J/KG), PWAT'S NEAR 1.6-1.8", AND DEEPLY MIXED
LOW LEVELS, STRONG TO DAMAGING DOWNBURST WINDS WILL BE POSSIBLE
IN THE STRONGEST STORMS, WITH MULTIPLE ALREADY BEING OBSERVED AS
OF WRITING THIS. THE QUICK MOVING SHORTWAVE IS ALREADY SHIFTING
EASTWARD, SO I WOULD NOT BE SURPRISED IF COVERAGE ACTUALLY
DECREASED SOME IN THE COMING HOURS, BUT AN ISOLATED STRONG STORM
COULD REMAIN POSSIBLE INTO THE EARLY EVENING HOURS.
AVIATION /19Z THURSDAY THROUGH TUESDAY/
MAINLY VFR CONDITIONS EXPECTED TO PERSIST OUTSIDE OF POSSIBLE
CONVECTION.
REGIONAL VISIBLE SATELLITE ALONG WITH RADAR COMPOSITE SHOWING
MUCH OF THE FORECAST AREA AREA THE TAF LOCATIONS ARE BEGINNING
TO GET ACTIVE THIS AFTERNOON WITH SHOWERS AND THUNDERSTORMS.
BASED ON THAT, ALL SITES WILL BE STARTING OFF WITH VCTS, ALONG
WITH A TEMPO GROUP THROUGH 22Z TO ACCOUNT FOR MVFR VISIBILITIES
AND GUSTY WINDS WITH ANY ACTIVITY THAT IMPACTS THE TAFS. OUTSIDE
OF THIS CONVECTION, VFR CONDITIONS SHOULD PREVAIL THROUGH THE
PERIOD. ADDITIONAL SHOWERS AND STORMS WILL BE POSSIBLE AGAIN
FRIDAY AFTERNOON, WITH POTENTIAL FOR GREATER COVERAGE AND
STRONGER STORMS WITH HEAVY RAINFALL. HAVE HANDLED WITH PROB30
FOR NOW THAT FAR OUT.
EXTENDED AVIATION OUTLOOK...THUNDERSTORM CHANCES REMAIN INTO
THE WEEKEND, WITH SCATTERED TO WIDESPREAD CONVECTION EXPECTED.
CAE WATCHES/WARNINGS/ADVISORIES
SC...NONE.
GA...NONE.
DISCUSSION...DH
AVIATION...73
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