194
FXUS62 KCAE 201827
AFDCAE
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE COLUMBIA SC
227 PM EDT WED MAY 20 2026
WHAT HAS CHANGED
RAIN BECOMING INCREASINGLY LIKELY FRIDAY AND SATURDAY WITH A
WEDGE BOUNDARY EXPECTED TO DROP INTO THE FORECAST AREA. AVIATION
DISCUSSION UPDATED FOR 18Z TAF ISSUANCE.
KEY MESSAGES
- 1. UNCERTAINTY IN TEMPERATURES FRIDAY AND THIS WEEKEND.
- 2. RAIN CHANCES INCREASE LATE WEEK ONWARD.
DISCUSSION
KEY MESSAGE 1: UNCERTAINTY IN TEMPERATURES FRIDAY AND THIS WEEKEND.
HIGHS TODAY AND THURSDAY WILL REMAIN ABOVE NORMAL BUT STILL
UNDER ANY HEAT ADVISORY THRESHOLDS.
AS HIGH PRESSURE MOVES INTO THE NORTHEAST LATE THIS WEEK, COLD
AIR DAMMING DEVELOPS OVER THE MID-ATLANTIC STATES PUSHING A
SURFACE BOUNDARY DOWN INTO THE CAROLINAS. THIS WOULD LEAD TO A
LARGE TEMPERATURE GRADIENT OVER THE FORECAST AREA. HOWEVER
BLENDED GUIDANCE HAS NEARLY THE ENTIRE FORECAST AREA IN THE 80S
OR LOW 90S FOR FRIDAY AND SATURDAY. THIS DETERMINISTIC GUIDANCE
MAY NOT BE PROPERLY SHOWING THE UNCERTAINTY OF WHERE THAT
BOUNDARY MAY SET UP. A PORTION OF THE FORECAST AREA COULD
STRUGGLE TO RISE OUT OF THE MID 70S FRIDAY AND POSSIBLY
SATURDAY GIVEN THAT THE WEDGE BOUNDARY TYPICALLY REMAINS IN
PLACE LONGER THAN MODELS SHOW. CONFIDENCE IN THE WEDGE HOLDING
IS INCREASED BY THE EXPECTATION OF RAIN FALLING THROUGH THE COOL
LOWER LEVELS.
KEY MESSAGE 2: RAIN CHANCES INCREASE LATE WEEK ONWARD.
UPPER RIDGING WILL SHIFT SLIGHTLY EASTWARD THURSDAY AND FRIDAY
ALLOWING DEEPER MOISTURE AND SHORTWAVE ENERGY TO MOVE OVER THE
FORECAST AREA. INCREASED MOISTURE AND BETTER UPPER SUPPORT
SHOULD ALLOW CONVECTION TO DEVELOP EACH AFTERNOON AS THE AIR
MASS BECOMES CONDITIONALLY UNSTABLE. FRIDAY AND FRIDAY NIGHT MAY
BE PARTICULARLY ACTIVE AS THE WEDGE BOUNDARY DISCUSSED IN KM1
PUSHES INTO THE AREA FROM THE NORTH AND A SERIES OF SHORTWAVES
MOVES OVER THE REGION. THIS SHOULD HELP SUSTAIN CONVECTION PAST
THE DIURNALLY FAVORED TIMEFRAME AND INTO THE OVERNIGHT PERIOD.
REFS MEAN SBCAPE VALUES RISE TO 750 TO 1250 J/KG EACH AFTERNOON.
WITH WEAK INSTABILITY AND IN A WEAKLY SHEARED ENVIRONMENT WE
SHOULD SEE THUNDERSTORMS DEVELOP BUT WE EXPECT THEM TO BE SUB-
SEVERE.
THE DEEPEST MOISTURE APPEARS TO MOVE INTO THE REGION ON SATURDAY
AS MOISTURE TRANSPORT STRENGTHENS OVER THE WEDGE BOUNDARY. THIS
SHOULD LEAD TO WIDESPREAD SHOWERS AND THUNDERSTORMS. DEEP LAYER
SHEAR WILL BE A LITTLE STRONGER SATURDAY, WITH SOME HELICITY
ENHANCEMENT ALONG THE FRONT. THERE IS A QUESTION AS TO HOW
UNSTABLE THE ENVIRONMENT WILL BE GIVEN THE EXPECTED WIDESPREAD
RAINFALL AND CLOUD COVER, BUT THERE WILL BE SOME POTENTIAL FOR
ORGANIZED CONVECTION AND SEVERE WEATHER SATURDAY AFTERNOON.
THE DEEPEST MOISTURE MOVES OUT OF THE REGION ON SUNDAY WITH
UPPER RIDGING BUILDING BACK IN OVER THE SOUTHEAST. PWAT VALUES
REMAIN ABOVE NORMAL ALLOWING SHOWERS AND THUNDERSTORMS TO
DEVELOP EACH AFTERNOON COINCIDING WITH DAYTIME HEATING. WITH
STRONGER RIDGING OVER THE AREA AND THE WEDGE BOUNDARY SHIFTING
BACK TO THE NORTH THERE SHOULD BE LOWER CONVECTIVE COVERAGE
SUNDAY AND EARLY NEXT WEEK COMPARED TO SATURDAY.
AVIATION /18Z WEDNESDAY THROUGH MONDAY/
VFR CONDITIONS CONTINUE TODAY WITH BRIEF RESTRICTIONS POSSIBLE
AGAIN EARLY THURSDAY MORNING.
FEW TO SCT CUMULUS ARE DEVELOPING THIS AFTERNOON WITH LIGHT
WINDS THAT ARE A BIT VARIABLE. 5-8 KT WINDS SHOULD BECOME A BIT
MORE SOUTHEASTERLY TO SOUTH-SOUTHEASTERLY IN THE COMING HOURS,
AS CUMULUS CONTINUE TO DEVELOP. THE LOW CHANCE FOR A STRAY
SHOWER THIS AFTERNOON EXISTS, BUT CONFIDENCE IN THESE DEVELOPING
REMAINS FAIRLY LOW. WINDS THIS EVENING AND TONIGHT BECOME LIGHT
AND VARIABLE AS PASSING CIRRUS MOVE INTO THE REGION. AS HAS
BEEN THE CASE MULTIPLE DAYS THIS WEEK, MORE PATCHY FOG/STRATUS
IS POSSIBLE TONIGHT INTO EARLY THURSDAY MORNING WITH PLENTY OF
LOW LEVEL MOISTURE IN PLACE. SREF AND HREF PROBABILITIES FOR
CEILINGS LESS THAN 500FT AGAIN APPROACH 40-60% AFTER 08-10Z,
MAINLY ACROSS THE SOUTHEASTERN MIDLANDS AND TOWARD THE SOUTHERN
CSRA. THE TYPICAL FOG PRONE SITES OF AGS/OGB ARE THE MOSTLY
LIKELY TO EXPERIENCE MVFR TO IFR RESTRICTIONS WHILE CONFIDENCE
AT THE OTHER SITES IS A BIT LOWER. ANY PATCHY RESTRICTIONS
SHOULD LIFT AFTER 12-14Z AS 3-5 KT WINDS OUT OF THE SOUTH TO
SOUTHWEST DEVELOP. SCT CUMULUS SHOULD DEVELOP THROUGH THE DAY
WHERE SHOWER/STORM CHANCES COULD INCREASE JUST AFTER THIS TAF
PERIOD.
EXTENDED AVIATION OUTLOOK...HIGH LOW LEVEL MOISTURE MAY BRING
MORE ROUNDS OF MORNING RESTRICTIONS FROM FOG/STRATUS INTO THE
WEEKEND. SCATTERED AFTERNOON SHOWERS AND STORMS BECOME POSSIBLE
TOMORROW WITH MORE CHANCES THIS WEEKEND.
CAE WATCHES/WARNINGS/ADVISORIES
SC...NONE.
GA...NONE.
DISCUSSION...CJR
AVIATION...DH
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