484
FXUS62 KCAE 212338
AFDCAE
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE COLUMBIA SC
738 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 00Z.
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 INTO 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 /00Z FRIDAY THROUGH TUESDAY/
GENERALLY VFR CONDITIONS EXPECTED THIS EVENING, WITH A FEW
SHOWERS-STORMS AROUND. MVFR-IFR STRATUS LIKELY EARLY FRIDAY
MORNING.
SCATTERED CONVECTION AND AREAS OF STRATUS HAVE DEVELOPED ACROSS
PORTIONS OF THE AREA TO THE NORTH AND WEST OF THE CWA THIS
AFTERNOON. ANY ACTIVITY SHOULD REMAIN AWAY FROM ALL TERMINALS.
THE SEA BREEZE IS CURRENTLY MAKING IT'S WAY THROUGH THE
COLUMBIA AREA CAUSING A FEW GUSTY WINDS ALONG THE WAY, BUT LIGHT
WINDS ARE EXPECTED TO DEVELOP OVERNIGHT. STRATUS ALSO MOVES IN
LATE TONIGHT INTO FRIDAY MORNING. MVFR CEILINGS ARE EXPECTED TO
BECOME WIDESPREAD AFTER 08Z, WITH THE GREATEST POTENTIAL FOR IFR
RESTRICTIONS APPEARING AT OGB. PATCHY FOG MAY ALSO DEVELOP,
MAINLY ACROSS THE SOUTHERN AND EASTERN PORTIONS OF THE AREA
WHERE LOW-LEVEL MOISTURE REMAINS FAVORABLE.
COLD AIR DAMMING CONDITIONS WILL SETTLE IN DURING THE DAY
FRIDAY, SUPPORTING PERSISTENT LOW STRATUS THROUGH AT LEAST MID-
MORNING. GRADUAL IMPROVEMENT WILL BEGIN AFTER 14-15Z WITH
SOUTHEAST WINDS PICKING BACK UP NEAR 5-8 KTS. ANOTHER ROUND OF
DIURNALLY DRIVEN CONVECTION IS EXPECTED TO DEVELOP FRIDAY
EVENING. CONFIDENCE IN DIRECT TERMINAL IMPACTS REMAINS LIMITED
AT THIS TIME, SO ONLY VCSH WAS MAINTAINED NEAR THE END OF THE
CURRENT TAF PERIOD.
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/CAL
AVIATION...ND
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