349
FXUS62 KCAE 201741
AFDCAE
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE COLUMBIA SC
141 PM EDT MON JUL 20 2026
WHAT HAS CHANGED
RAIN CHANCES RAMP UP MID WEEK WITH SHOWERS AND THUNDERSTORMS
LIKELY THURSDAY AND FRIDAY. AVIATION DISCUSSION UPDATED FOR 18Z
TAFS.
KEY MESSAGES
- 1. ISOLATED TO WIDELY SCATTERED CONVECTION POSSIBLE TODAY AND
TUESDAY WITH HOT/HUMID CONDITIONS CONTINUING.
- 2. RAIN CHANCES INCREASE WEDNESDAY AND REMAIN HIGH THROUGH THE
WEEKEND. SEVERE WEATHER WILL BE POSSIBLE ON WED AND THU.
DISCUSSION
KEY MESSAGE 1: ISOLATED TO WIDELY SCATTERED CONVECTION POSSIBLE
TODAY AND TUESDAY WITH HOT/HUMID CONDITIONS CONTINUING.
MONDAY: ISOLATED TO WIDELY SCATTERED AFTERNOON TO EVENING
THUNDERSTORMS REMAIN POSSIBLE THIS AFTERNOON AND EVENING WHILE
HOT AND HUMID CONDITIONS CONTINUE. AS A POCKET OF DRY AIR FROM
THE NW MOVES ACROSS THE SE INTO THE MID-ALANTIC DUE TO AN AREA
OF HIGH PRESSURE WILL LIMIT CONVECTION. WITH THE COMBINATION OF
WEAK FORCING, MODEST INSTABILITY, DIURNAL HEATING, AND LOW LEVEL
MOISTURE WILL SUPPORT ISOLATED THUNDERSTORM DEVELOPMENT,
ESPECIALLY ALONG THE I-95 CORRIDOR. PWAT VALUES ARE EXPECTED TO
REMAIN BETWEEN 1.8-2.05" WHICH WILL ALLOW FOR DEVELOPING STORMS
TO PRODUCE LOCALIZED HEAVY RAINFALL AND POSSIBLE FLASH FLOOD
THREATS. OUTSIDE OF THUNDERSTORMS, TEMPERATURES ARE EXPECTED TO
BE IN THE MID 90'S AND APPARENT TEMPERATURES JUST UNDER HEAT
ADVISORY CRITERIA.
TUESDAY: AS THE GULF SYSTEM DRIFTS SLIGHTLY WESTWARD, MODELS
PROJECT A DRY SLOT OF AIR ADVECTING UP INTO THE FORECAST AREA
DURING THE DAY ON TUESDAY. PWAT VALUES AROUND 1.5 INCHES OVER
MUCH OF THE AREA SHOULD LIMIT THE EXTENT OF CONVECTIVE
DEVELOPMENT. THAT SAID WE COULD SEE A FEW ISOLATED
THUNDERSTORMS, PARTICULARLY ALONG THE SEA BREEZE TUESDAY
AFTERNOON. THE THREATS OF SEVERE WEATHER AND HEAVY RAIN ARE
LOW. THE DRIER AIR MASS SHOULD ALSO ALLOW DEWPOINTS TO MIX INTO
THE 60S REDUCING THE CHANCES OF MEETING HEAT ADVISORY CONDITIONS
DESPITE HIGHS MAINLY IN THE MID 90S.
KEY MESSAGE 2: RAIN CHANCES INCREASE WEDNESDAY AND REMAIN HIGH
THROUGH THE WEEKEND. SEVERE WEATHER WILL BE POSSIBLE ON WED AND
THU.
THE OVERALL SYNOPTIC PATTERN REMAINS UNCHANGED IN GLOBAL
ENSEMBLES FOR LATER THIS WEEK AND THE WEEKEND. A STRONG UPPER
LEVEL TROUGH WILL LIKELY EXTEND FROM THE EASTERN GREAT LAKES
DOWN INTO THE MID-ATLANTIC. THE ASSOCIATED COLD FRONT WILL DIVE
DOWN INTO THE MID-ATLANTIC AND COULD NEAR THE FA WEDNESDAY
THROUGH THURSDAY. IVT VALUES FROM THE NAEFS AHEAD OF THE FRONT
ARE NEAR THE 90TH TO 99TH PERCENTILE OF CLIMATOLOGY. THERE
REMAINS SOME UNCERTAINTY IN THE DEPTH OF THE UPPER TROUGH AND
HOW FAR SOUTH THE FRONT WILL PUSH BUT ON AVERAGE THE FRONT IS
EXPECTED TO GET NEAR ENOUGH TO THE FA TO SUPPORT WIDESPREAD
SHOWERS AND THUNDERSTORMS LATE WEDNESDAY AND THURSDAY.
SEASONABLE INSTABILITY AND MODERATE DEEP LAYER SHEAR SHOULD
SUPPORT SOMEWHAT ORGANIZED THUNDERSTORMS AND POSSIBLY SEVERE
WEATHER.
GLOBAL MODELS DEPICT THE FRONTAL BOUNDARY STALLING NEAR OR OVER
THE FA ON THURSDAY AS A SHORTWAVE PASSES. CONTINUED MOISTURE
ADVECTION INTO THE REGION, AND CONVERGENCE ALONG THE FRONT
SUPPORTS WIDESPREAD THUNDERSTORM CHANCES WITH HEAVY RAINFALL
POSSIBLE. WITH THE REGION REMAINING IN NORTHWEST FLOW INTO THE
WEEKEND, A SERIES OF SHORTWAVES ARE EXPECTED TO CONTINUE PUSHING
THROUGH, ENHANCING CONVECTIVE DEVELOPMENT POTENTIALLY OUTSIDE
OF TYPICAL DIURNAL HOURS.
AVIATION /18Z MONDAY THROUGH SATURDAY/
VFR CONDITIONS EXPECTED OUTSIDE OF ISOLATED CONVECTION....
RADAR THIS AFTERNOON IS BEGINNING TO PICK UP ON SHOWERS ACROSS
PORTIONS OF THE FORECAST AREA, MAINLY NORTHEAST OF CAE/CUB. A
PROB30 FOR SHOWERS WAS ADDED TO CAE/CUB FOR THE REMAINDER OF THE
AFTERNOON BASED ON CONVECTIVE TRENDS. GUIDANCE APPEARS BULLISH
IN THUNDERSTORM DEVELOPMENT ACROSS THE SOUTHEASTERN MIDLANDS,
INCLUDING AROUND OGB, SO ADDED A PROB30 FOR THUNDERSTORMS
THERE. CURRENTLY A DRY AFTERNOON IS INDICATED AT AGS/DNL/AIK BUT
WILL AMEND IF NEEDED. THE BREEZY CONDITIONS HAVE NOT MANIFESTED
AS EXPECTED SO OPTED TO DROP WINDS AT ALL TERMINALS THIS
AFTERNOON. EXPECT MAINLY LIGHT WINDS AND SCATTERED MID TO HIGH
LEVEL CLOUDS TONIGHT WITH SOUTHWESTERLY WINDS RETURNING ON
TUESDAY.
EXTENDED AVIATION OUTLOOK...POTENTIAL FOR RESTRICTIONS FROM
SHOWERS AND THUNDERSTORMS CONTINUES WITH THE THREAT INCREASING
FOR THE MID TO LATE WEEK PERIOD.
CAE WATCHES/WARNINGS/ADVISORIES
SC...NONE.
GA...NONE.
DISCUSSION...MK/CJR
AVIATION...7
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