269
FXUS62 KCAE 211837
AFDCAE
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE COLUMBIA SC
237 PM EDT THU MAY 21 2026
WHAT HAS CHANGED
RAINFALL AMOUNTS HAVE INCREASED FOR THIS WEEKEND, HOWEVER THOSE
HIGHER AMOUNTS WILL BE LOCALIZED. AVIATION UPDATED FOR 18Z.
KEY MESSAGES
- 1. SHOWERS AND THUNDERSTORMS EXPECTED THROUGH NEXT WEEK
- 2. UNCERTAINTY IN TEMPERATURES NORTH OF I-20 ON FRI AND SAT
DISCUSSION
KEY MESSAGE 1: SHOWERS AND THUNDERSTORMS EXPECTED THROUGH NEXT
WEEK
MEAN PWAT VALUES FROM THE GEFS AND ECMWF ENSEMBLES RISE TO ABOVE
1.5 INCHES FRIDAY AND REMAIN ABOVE NORMAL THROUGH MUCH OF NEXT
WEEK. AS AN UPPER LEVEL RIDGE SHIFTS SLIGHTLY EAST TONIGHT AND
FRIDAY, MOISTURE ADVECTION STRENGTHENS OVER THE SOUTHEAST. AT
THE SAME TIME, HIGH PRESSURE OVER THE GREAT LAKES WILL SHIFT
TOWARD NEW ENGLAND AND BEGIN TO RIDGE DOWN THE EAST COAST. THE
RESULT IS A COLD AIR DAMMING SCENARIO OVER THE MID-ATLANTIC
STATES AND INTO THE CAROLINAS. A VARIETY OF TRIGGERS AT THE
SURFACE INCLUDING THE SEA BREEZE AIDED BY SE LOW LEVEL FLOW
WILL SUPPORT CONVECTION EACH DAY THROUGH THE EXTENDED. THE
HIGHEST RAINFALL CHANCES APPEAR TO BE FRIDAY NIGHT INTO SATURDAY
AS THE DEEPER MOISTURE MOVES ACROSS THE FA AND SEVERAL
SHORTWAVES SUPPORT CONVECTIVE ACTIVITY. THE DEEPEST MOISTURE
MOVES OUT OF THE AREA ON SUNDAY WITH UPPER RIDGING BUILDING
BACK OVER THE SOUTHEAST. WITH PWAT VALUES STILL ABOVE NORMAL AND
ONSHORE FLOW STILL IN PLACE WE CAN EXPECT AT LEAST SCATTERED
SHOWERS AND THUNDERSTORMS EACH DAY INTO EARLY NEXT WEEK.
THE SEVERE THREAT EACH DAY WILL BE LOW. ISOLATED DOWNBURST
WINDS WILL BE THE MAIN THREAT. SATURDAY MAY BE THE GREATEST
CHANCE OF ORGANIZED MULTI-CELL CLUSTERS WITH DEEP LAYER SHEAR
AROUND 20 KTS. HOWEVER WITH WIDESPREAD CLOUD COVER AND RAIN
ANTICIPATED, LAPSE RATES ARE NOT EXPECTED TO SUPPORT A
WIDESPREAD SEVERE THREAT.
AS CAMS BEGIN TO COME IN FOR LATE THIS WEEK AND THE WEEKEND WE
ARE BEGINNING TO SEE THE CONVECTIVE NATURE OF THE QPF. IN
GENERAL OVER THE NEXT THREE DAYS, WE MAY SEE 0.5 TO 1 INCH OF
RAINFALL BUT IT WILL BE VARIED WIDELY WITH LOCALIZED HIGHER AND
LOWER AMOUNTS.
KEY MESSAGE 2: UNCERTAINTY IN TEMPERATURES NORTH OF I-20 ON FRI
AND SAT
AS DISCUSSED IN KM1 THE EDGE OF THE CAD WILL PUSH INTO THE
CAROLINAS ON FRIDAY. THE EXACT TIMING AND LOCATION OF THE
BOUNDARY BY FRIDAY MORNING IS UNCERTAIN WITH A LARGE SPREAD IN
TEMPERATURE GUIDANCE FOR THE CATAWBA REGION. THE NBM IS
FAVORING THE WARMER SIDE OF THE MODEL SPECTRUM HOWEVER WE KNOW
THAT THIS SETUP TYPICALLY LEADS TO TEMPERATURES COOLER THAN MOST
MODELS SHOW. DESPITE LOWERING FORECAST HIGH TEMPS, AREAS SUCH
AS NORTHERN LANCASTER COUNTIES MAY STILL BE TOO WARM. ANOTHER
COMMON ISSUE WITH MODEL GUIDANCE IN CAD SETUPS IS ERODING THE
WEDGE TOO QUICKLY THE FOLLOWING DAY. SO WE HAVE FAVORED COOLER
TEMPERATURES AGAIN FOR THE NORTHERN FA ON SATURDAY.
AVIATION /18Z THURSDAY THROUGH TUESDAY/
GENERALLY VFR CONDITIONS EXPECTED THIS AFTERNOON AND EVENING,
WITH A FEW SHOWERS-STORMS AROUND. MVFR-IFR STRATUS LIKELY EARLY
FRIDAY MORNING.
A TYPICAL SUMMER DAY CONTINUES THIS AFTERNOON WITH SOME STRATO-
CU AND A FEW SHOWERS AND STORMS ACROSS THE AREA. WINDS WILL
CONTINUE TO REMAIN FAIRLY LIGHT AND VARIABLE FROM THE SOUTHWEST
TO SOUTHEAST, GUSTS UP TO 10 KNOTS. SHOWER AND STORM COVERAGE
WILL INCREASE THIS AFTERNOON BUT STILL ONLY INCLUDED A PROB30
FOR ALL TAF SITES EXCEPT OGB. LIGHT WINDS EXPECTED OVERNIGHT
BEFORE STRATUS MOVES IN EARLY FRIDAY. AT LEAST MVFR CIGS LIKELY
FOR ALL SITES AFTER 0800Z WITH IFR LIKELY AT OGB. WITH WEAK
WINDS IN THE MORNING, STRATUS WILL LINGER THROUGH ROUGHLY 1500Z.
EXTENDED AVIATION OUTLOOK...ABUNDANT LOW LEVEL MOISTURE WILL
BRING MORE ROUNDS OF MORNING RESTRICTIONS FROM FOG/STRATUS INTO
THE WEEKEND ALONG WITH SCATTERED AFTERNOON SHOWERS AND STORMS
POSSIBLE EACH DAY THROUGH THE WEEKEND.
CAE WATCHES/WARNINGS/ADVISORIES
SC...NONE.
GA...NONE.
DISCUSSION...CJR
AVIATION...42
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