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FXUS62 KCHS 121115
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
715 AM EDT SAT SEP 12 2026
WHAT HAS CHANGED
AVIATION SECTION UPDATED FOR THE 12Z TAFS.
KEY MESSAGES
- 1) THE RISK FOR SHOWERS AND THUNDERSTORMS WILL CONTINUE
THROUGH THE WEEKEND.
DISCUSSION
KEY MESSAGE 1: THE RISK FOR SHOWERS AND THUNDERSTORMS WILL CONTINUE
THROUGH THE WEEKEND.
TODAY: SATELLITE WATER VAPOR SHOWED A MID-LEVEL TROUGH
EXTENDING ACROSS THE MISSISSIPPI RIVER VALLEY, TRACKING EAST.
EAST OF THE TROUGH, A PLUME OF DEEP MOISTURE COVERED A LARGE
AREA FROM THE GULF ACROSS THE SOUTHEAST U.S., PW VALUES BETWEEN
2-2.2" ACROSS SE GA/SC. RUC40 GUIDANCE INDICATES A FEW VORT
MAXES WITHIN THE MOISTURE PLUME, WITH THE CONSENSUS OF THE
GUIDANCE INDICATING THAT ONE OR TWO DISTURBANCES TRACKING OVER
SE GA/SC THIS AFTERNOON. THE APPROACH AND PASSAGE OF THESE MID-
LEVEL DISTURBANCES COMBINED WITH THE SEA BREEZE SHOULD FOCUS THE
DEVELOPMENT OF CONVECTION. MLCAPE DURING THE HEAT OF THE
AFTERNOON IS FORECAST TO RANGE FROM 1500 J/KG INLAND TO 2500
J/KG ALONG THE COAST. GIVEN THE DEEP MOISTURE, DCAPE VALUES ARE
FORECAST TO REMAIN LESS THAN 1000 J/KG. THE PRIMARY HAZARD THIS
AFTERNOON WILL BE THE POTENTIAL FOR EXCESSIVE RAINFALL RATES,
AIDED BY HIGH PW VALUES AND 850-300MB RH IN EXCESS OF 70%.
ISOLATED LOCATIONS COULD SEE RAINFALL AMOUNTS EXCEED THREE
INCHES. BY LATE THIS EVENING, CONVECTION SHOULD DISSIPATE WITH
THE SPREADING OF OUTFLOW BOUNDARIES AND DIURNAL COOLING.
SUNDAY: THE MID-LEVELS WILL CONSIST OF A WEAK TROUGH MOVING OVER OUR
AREA IN THE MORNING, THEN OFFSHORE DURING THE AFTERNOON. THE SURFACE
PATTERN WILL BE RATHER DIFFUSE, WITH EITHER A WEAK FRONT WELL TO OUR
NORTH OR WEAK SURFACE TROUGHING OVER THE SOUTHEAST U.S.
SOUTHWESTERLY FLOW WILL CAUSE DEEP MOISTURE TO BE OVER OUR AREA IN
THE MORNING. PWATS SHOULD EASILY BE ABOVE 2". THIS IS WELL ABOVE
NORMAL PER CHS SOUNDING CLIMATOLOGY AND ABOUT 2 STANDARD DEVIATIONS
PER NAEFS. HOWEVER, LOWER PWATS WILL BUILD IN FROM THE WEST DURING
THE AFTERNOON, KEEPING THE HIGHEST PWATS ALONG THE IMMEDIATE COAST,
BEFORE THEY ARE PUSHED OFFSHORE IN THE EVENING. THE DETERMINISTIC
MODELS AND CAMS DIFFER SOMEWHAT ON THE AMOUNT OF SHOWER AND
THUNDERSTORM COVERAGE. BUT MOST POINT TO SCATTERED COVERAGE FORMING
NEAR THE COAST IN THE AFTERNOON, THEN SHIFTING OFFSHORE AND
DISSIPATING IN THE EVENING. HIGH TEMPERATURES WILL BE A FEW DEGREES
ABOVE NORMAL, LEADING TO MODEST INSTABILITY. ADDITIONALLY, HIGHER
DCAPES BUILD IN FROM THE WEST DURING THE AFTERNOON. SO WHILE WE'RE
NOT EXPECTING WIDESPREAD SEVERE WEATHER, THERE COULD BE A FEW HOUR
WINDOW WHERE STRONG TO MARGINALLY SEVERE THUNDERSTORMS CANNOT BE
RULED OUT ALONG THE COAST. LOCALLY HEAVY RAINFALL WILL ALSO BE
POSSIBLE. BUT THE STEERING LEVEL WINDS MAY BE JUST STRONG ENOUGH TO
LIMIT SIGNIFICANT FLOODING.
AVIATION /12Z SATURDAY THROUGH WEDNESDAY/
12Z TAFS: LIGHT SOUTHWEST WINDS WITH VFR CEILINGS AT KCHS AND
KJZI THIS MORNING, KSAV SHOULD REMAIN MOSTLY SUNNY. THIS
AFTERNOON, SHOWERS AND THUNDERSTORMS SHOULD FOCUS ALONG THE SEA
BREEZE AND APPROACHING VORT MAXES. EACH TERMINAL WILL FEATURE A
PROB30 BETWEEN 17-23Z FOR TSRA. ANY THUNDERSTORM MAY BRING GUSTY
WINDS AND SOME PERIODS OF RESTRICTIONS DURING MODERATE TO HEAVY
DOWNPOURS. EACH TAF, WILL INDICATE STEADY SOUTH WINDS FOLLOWING
THE SEA BREEZE.
EXTENDED AVIATION OUTLOOK: PERIODIC FLIGHT RESTRICTIONS WILL BE
POSSIBLE SUNDAY AFTERNOON DUE TO SHOWERS AND THUNDERSTORMS. DRIER
CONDITIONS RETURN ON MONDAY, POSSIBLY PERSISTING THROUGH
WEDNESDAY.
MARINE
TODAY AND TONIGHT: THE PRESSURE PATTERN WILL GENERALLY SUPPORT SOUTH-
SOUTHWEST WINDS BETWEEN 10 TO 15 KTS ACROSS THE MARINE ZONES. WAVE
HEIGHTS ARE FORECAST TO REMAIN BETWEEN 2 TO 3 FT.
EXTENDED MARINE: THE SYNOPTIC PATTERN WILL BE UNSETTLED ON SUNDAY,
BUT MODEST WINDS AND SEAS ARE EXPECTED. WINDS WILL EASE MONDAY
MORNING AND AFTERNOON, ALONG WITH SEAS TRENDING LOWER. BUT THIS WILL
BE SHORT-LIVED BECAUSE HIGH PRESSURE PASSING TO OUR NORTH WILL CAUSE
WINDS TO SHIFT TO THE NORTHEAST LATE MONDAY NIGHT AND SURGE. A
STRONG BREEZE WILL PERSIST TUESDAY INTO WEDNESDAY, WITH WIND-DRIVEN
SEAS BUILDING DURING THIS TIME PERIOD. SMALL CRAFT ADVISORIES WILL
BE NEEDED FOR MOST OF OUR WATERS BEGINNING TUESDAY.
CHS WATCHES/WARNINGS/ADVISORIES
GA...NONE.
SC...NONE.
MARINE...NONE.
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