511
FXUS62 KCHS 060754
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
354 AM EDT TUE MAY 6 2025
SYNOPSIS
A COLD FRONT WILL STALL JUST OFFSHORE AS HIGH PRESSURE
CONTINUES TO BUILD INTO THE REGION. ANOTHER COLD FRONT AND AN
UPPER-LEVEL LOW WILL APPROACH FROM THE WEST THURSDAY AND CAUSE
AN UNSETTLED WEATHER PATTERN TO PERSIST INTO THE WEEKEND.
NEAR TERM /THROUGH TONIGHT/
TODAY: ALOFT, THE LOW SITUATED OVER THE OH VALLEY WILL START TO
LIFT TO THE NORTHEAST AS SHORTWAVE RIDGING SHIFTS ACROSS THE
LOWER MS VALLEY. AT THE SURFACE, WEAK HIGH PRESSURE WILL PREVAIL
ACROSS THE FORECAST AREA. OVERALL, THE DAY SHOULD BE PRETTY
QUIET AND THE SUITE OF HI-RES MODELS FAVOR A DRY FORECAST. MODEL
SOUNDINGS FEATURE WARM PROFILES AS WELL AS AN INVERSION
CENTERED AROUND 750 MB. THE GRADIENT ACROSS THE REGION IS QUITE
WEAK AND THE MORNING SHOULD SEE NOTHING MORE THAN LIGHT AND
VARIABLE WINDS. BY THE AFTERNOON THE SEA BREEZE WILL DEVELOP AND
STEADILY PUSH INLAND THROUGH THE AFTERNOON. ANOTHER DAY OF
ABOVE NORMAL TEMPERATURES IS EXPECTED, AND THE FORECAST FEATURES
MOSTLY MID 80S AWAY FROM THE IMMEDIATE COAST. SIMILAR TO
YESTERDAY, A FEW UPPER 80S WILL BE POSSIBLE ACROSS PORTIONS OF
SOUTHEAST GA.
TONIGHT: THE OVERNIGHT PERIOD SHOULD BE QUIET AS WELL AS WEAK
HIGH PRESSURE CONTINUES. AS SUNRISE WEDNESDAY APPROACHES, WE
WILL HAVE TO WATCH FOR AN UPSTREAM CONVECTIVE COMPLEX AND ITS
PROGRESSION ACROSS THE LOWER MS VALLEY AND THE DEEP SOUTH. HI-
RES MODEL SOLUTIONS GENERALLY AGREE THAT ANY RESIDUAL
PRECIPITATION ASSOCIATED WITH THIS FEATURE SHOULD BE MORE OF AN
ISSUE INTO WEDNESDAY, BUT THERE ARE DIFFERENCES REGARDING ITS
FORWARD SPEED, TRAJECTORY, AND STRENGTH. THE FORECAST DOES
FEATURE SOME 20 PERCENT CHANCES ACROSS THE FAR WESTERN PORTION
OF THE AREA, BUT CONFIDENCE IN THIS IS QUITE LOW. LOWS ARE
FORECAST TO RANGE FROM THE UPPER 50S INLAND TO THE MID TO UPPER
60S ALONG THE IMMEDIATE COAST.
SHORT TERM /WEDNESDAY THROUGH FRIDAY/
WEDNESDAY: ALOFT, A CLOSED UPPER-LVL LOW WILL SLOWLY SHIFT
NORTHEASTWARD TOWARDS NEW ENGLAND AND THEN EVENTUALLY OFFSHORE.
THIS SHIFT WILL PLACE THE REGION IN THE RIGHT-ENTRANCE OF THE
DEPARTING JET STREAK AND ALLOW MORE UNSETTLED WEATHER PATTERN TO
DEVELOP. WEST-SOUTHWESTERLY FLOW WILL ALLOW MOISTURE TO SURGE
INTO THE REGION FROM THE GULF. ADDITIONALLY, AT THE SURFACE, A
WEAK ALMOST STATIONARY FRONT WILL LINGER NEARBY AND PROVIDE AN
ADDITIONAL FORCING MECHANISM FOR SHOWERS AND THUNDERSTORMS TO
DEVELOP. THERE IS GOOD AGREEMENT AMONGST THE MODELS
(GFS/CAMS/HREF) OF SHOWERS AND THUNDERSTORMS DEVELOPING IN THE
MORNING (~12-13Z) ACROSS SOUTHEAST GEORGIA AND THEN INTO
SOUTHEAST SOUTH CAROLINA SHORTLY AFTER (~14-15Z). WITH THE LACK
OF INSTABILITY AND SHEAR, THE STORMS THAT DO DEVELOP WILL REMAIN
ON THE NON-SEVERE SIDE. DESPITE THE LACK OF SUNSHINE, HIGHS
WILL STILL CLIMB INTO THE UPPER 70S TO LOW 80S. SHOWERS AND
THUNDERSTORMS SHOULD MOVE OFFSHORE AT NIGHT AND LOWS WILL DROP
OUT INTO THE LOW TO MID 60S OVERNIGHT.
THURSDAY: AS YET ANOTHER UPPER-LVL LOW SITUATED OVER THE
MISSISSIPPI VALLEY APPROACHES THE REGION, THE ALMOST STATIONARY
FRONT WILL CONTINUE TO LINGER OFFSHORE. THIS IS WHERE THE
FORECAST GETS A LITTLE TRICKY .. SOME MODEL GUIDANCE SHOWS SOME
SHOWERS AND THUNDERSTORMS DEVELOPING THURSDAY AFTERNOON WHILE
OTHERS ARE NOT. THUS, POPS HAVE BEEN LOWERED A BIT TO REFLECT
THESE CHANGES. HIGHS WILL REACH INTO THE LOW TO MID 80S AND
OVERNIGHT LOWS WILL DROP INTO THE LOW TO MID 60S INLAND AND
UPPER 60S CLOSER TO THE COASTLINE.
FRIDAY: THIS SEEMS LIKE THE MAIN EVENT DAY. AS THIS UPPER-LVL
LOW SITUATES ITSELF IN THE DEEP SOUTH, AN ASSOCIATED COLD FRONT
WILL PASS THROUGH THE REGION THROUGHOUT THE DAY. WHILE
GFS/ECMWF/NAM12KM ARE IN GOOD AGREEMENT THAT SHOWERS AND
THUNDERSTORMS WILL DEVELOP IN THE EARLY MORNING AND PERSIST
THROUGHOUT THE DAY, THE ECMWF IS THE ONLY ONE SHOWING SOMEWHAT A
SEVERE THREAT. HOWEVER, EVEN THOUGH THIS IS STILL FAR OUT TO
TELL EXACTLY WHAT WILL HAPPEN, THIS CONFIDENCE IS INCREASING IN
SOME SEVERE THUNDERSTORM DEVELOPMENT. ADDITIONALLY, WPC HAS
HIGHLIGHTED THE REGION UNDER A MARGINAL RISK FOR EXCESSIVE
RAINFALL. WITH PWAT VALUES RANGING ~1.50-1.75 INCHES AND A GOOD
AMOUNT OF GUIDANCE INDICATING THAT THIS CUT-OFF LOW WILL
CONTINUE SIT SOMEWHERE OVER THE DEEP SOUTH FOR THE NEXT COUPLE
DAYS (ADVECTING MOIST SOUTHWESTERLY FLOW INTO THE REGION),
DECENT AMOUNTS OF RAINFALL COULD BE SEEN. RAINFALL AMOUNTS FOR
FRIDAY RANGE FROM 0.75 TO 1.0 INCHES, HOWEVER THIS WILL PROBABLY
CHANGE SOME IN THE NEXT COUPLE DAYS AS THERE IS STILL SOME
UNCERTAINTY REGARDING HOW LONG THE LOW WILL HANGOUT IN THE DEEP
SOUTH. EXPECT TEMPERATURES WILL BE NEAR NORMAL ON FRIDAY.
LONG TERM /FRIDAY NIGHT THROUGH MONDAY/
AS THIS CUT-OFF LOW CONTINUES TO SIT ACROSS THE DEEP SOUTH AND
A FRONTAL BOUNDARY LINGERS NEARBY, EXPECT AN EXTENDED PERIOD OF
UNSETTLED, WET WEATHER. THERE IS POTENTIAL TO SEE RAINFALL
AMOUNTS 2+ INCHES IN SOME SPOTS OVER THE WEEKEND AND INTO NEXT
WEEK. EXPECT MORE CONFIDENCE TO INCREASE IN THE NEXT COUPLE DAYS
WITH HOW LONG THIS LOW SITS ACROSS THE DEEP SOUTH AND WHAT THIS
MEANS FOR THE REGION. TEMPERATURES WILL BE NEAR AND BELOW
NORMAL.
AVIATION /08Z TUESDAY THROUGH SATURDAY/
VFR CONDITIONS ARE EXPECTED TO PREVAIL AT KCHS, KJZI, AND KSAV
THROUGH 06Z WEDNESDAY.
EXTENDED AVIATION OUTLOOK: EXPECT MULTIPLE ROUNDS OF SCATTERED
SHOWERS AND THUNDERSTORMS ASSOCIATED WITH A NEARBY FRONT TO
DEVELOP THROUGH THE PERIOD. PERIODS OF MVFR/IFR CONDITIONS ARE
POSSIBLE AT CHS/JZI/SAV EACH DAY.
MARINE
TODAY THROUGH TONIGHT: OVERALL, VERY QUIET MARINE CONDITIONS
THROUGH THE PERIOD. FLOW COULD BE NORTHEASTERLY THIS MORNING
ACROSS THE LOCAL WATERS, BUT WILL TURN SOUTHEASTERLY THIS
AFTERNOON WITH THE DEVELOPMENT OF THE SEA BREEZE. SPEEDS WILL BE
HIGHEST ALONG THE LAND/SEA INTERFACE WITH UP TO 10-15 KNOTS
EXPECTED. OVERNIGHT, THE GRADIENT REMAINS QUITE WEAK AND WIND
SPEEDS WILL BE 5 KNOTS OR LESS. SEAS ARE EXPECTED TO AVERAGE 2-3
FEET THROUGH THE PERIOD, HIGHEST ACROSS THE OUTER WATERS.
THURSDAY THROUGH SUNDAY: ALOFT, AS AN UPPER-LVL SLOWLY DRIFTS
TOWARDS OFF THE NEW ENGLAND COASTLINE, ANOTHER UPPER-LVL LOW
WILL APPROACH THE REGION. AT THE SURFACE, A NEARBY STATIONARY
FRONT WILL SLOWLY DRIFT BACK TOWARD THE SOUTHEAST COASTLINE MID-
WEEK. THIS WILL SUPPORT UNSETTLED WEATHER CONDITIONS ACROSS
COASTAL WATERS AS SHOWERS AND THUNDERSTORMS COULD POSSIBLE
DEVELOP EACH DAY. HOWEVER, CONDITIONS SHOULD REMAIN UNDER SMALL
CRAFT ADVISORY THRESHOLDS, EXCEPT FOR SATURDAY AFTERNOON WITH
SOME 6 FOOTERS APPROACHING THE NEARSHORE AND OFFSHORE CHARLESTON
WATERS. IN GENERAL, OFFSHORE WINDS WILL PEAK ~10 TO 15 KT. ON
SATURDAY, GUSTS COULD BECOME SLIGHTLY STRONGER, ESPECIALLY NEAR
THE COAST WITH A SEA BREEZE CIRCULATION (~20 KT). SEAS WILL
SLOWLY BUILD FROM 2 TO 3 FT MID WEEK TO 3 TO 5 FT THIS WEEKEND.
CHS WATCHES/WARNINGS/ADVISORIES
GA...NONE.
SC...NONE.
MARINE...NONE.
NEAR TERM...BSH
SHORT TERM...DENNIS
LONG TERM...DENNIS
AVIATION...BSH/DENNIS
MARINE...BSH/DENNIS
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