945
FXUS62 KCHS 070740
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
340 AM EDT WED MAY 7 2025
SYNOPSIS
A FRONT WILL REMAIN STALLED NEARBY THROUGH THE WEEKEND AS CUT-
OFF LOW CONTINUES TO MOVE CLOSER TO THE REGION. THIS WILL ALLOW
AN UNSETTLED, WET PATTERN TO PERSIST OVER THE NEXT SEVERAL DAYS.
NEAR TERM /THROUGH TONIGHT/
TODAY: ALOFT, WHILE SHORTWAVE RIDGING WILL PUSH ACROSS THE
SOUTHEAST, MODEL GUIDANCE DEPICTS EMBEDDED SHORTWAVE ENERGY AND
ASSOCIATED VORT MAX PASSING THROUGH THE AREA LIKELY A REMNANT OF
THE ONGOING UPSTREAM CONVECTIVE COMPLEX. AT THE SURFACE, THE
SETUP IS QUITE WEAK AND NEBULOUS WITH A SUBTLE BOUNDARY SITUATED
TO THE SOUTH THAT RUNS ACROSS SOUTH GA BACK INTO AL. OVERALL,
THERE REALLY ISN'T ANY SIGNIFICANT FORCING MECHANISM TO FOCUS ON
AND INSTEAD IT APPEARS OUR PRECIP CHANCES WILL BE DEPENDENT ON
THE ARRIVAL OF THE REMNANT UPSTREAM CONVECTIVE COMPLEX AND ITS
POTENTIAL INTERACTION WITH THE SEA BREEZE. HI-RES MODEL GUIDANCE
IS IN GOOD GENERAL AGREEMENT THAT THE ONGOING UPSTREAM
CONVECTION WILL STEADILY DIMINISH AS IT PUSHES INTO THE FAR
WESTERN ZONES AROUND MID MORNING. GUIDANCE THEN HIGHLIGHTS THE
GA COAST UP THROUGH APPROXIMATELY THE BEAUFORT COUNTY COAST FOR
THE BEST CONVECTIVE DEVELOPMENT BEGINNING AROUND OR JUST AFTER
MIDDAY AS THE REMNANT COMPLEX, OR ITS OUTFLOW, INTERACTS WITH
THE SEA BREEZE AND ALLOWS FOR NEW CONVECTION TO INITIATE. SO
THERE IS REASONABLE CONFIDENCE IN CONVECTION IN THIS GA COASTAL
AREA, BUT THE FURTHER NORTH YOU GO IT IS QUITE UNCLEAR IF
CONVECTION WILL DEVELOP AND HOW WIDESPREAD IT MIGHT BE. WE HAVE
THE HIGHEST CHANCES ALIGNED ALONG THE AFOREMENTIONED COASTAL
AREA, INTO THE 60-80 PERCENT RANGE, WITH GENERALLY NOTHING MORE
THAN 20-40 PERCENT ELSEWHERE. PART OF THIS IS BECAUSE MODEL
SOUNDINGS ARE QUITE UNIMPRESSIVE AS YOU GET UP TOWARD THE
CHARLESTON COUNTY COAST WITH LITTLE TO NO INSTABILITY. EVEN
ALONG THE GA COAST, SOURCES SUCH AS THE HREF SUGGEST MODEST
INSTABILITY OF AROUND 1,000 J/KG. THERE IS A BIT OF SHEAR, WITH
SOUNDINGS SUGGESTING ~25 KNOTS THROUGH THE 0-6 KM LAYER. OVERALL
THE SEVERE POTENTIAL IS LOW EVEN ALONG THE GA COAST, BUT THERE
COULD BE ONE OR TWO STRONGER STORMS. DEPENDING ON HOW CONVECTION
DEVELOPS AND EVOLVES, THERE IS POTENTIAL FOR LOCALIZED HEAVY
RAINFALL AND 0.50-1.00" OF RAIN ALONG THE GA COAST WHERE STORMS
TRACK. ELSEWHERE, RAINFALL SHOULD BE LIGHT, NO MORE THAN A TENTH
OF AN INCH. HIGHS ARE FORECAST TO REACH THE UPPER 70S TO LOW
80S, THOUGH SOME DISRUPTION TO THE TYPICAL DIURNAL TREND IS
EXPECTED ALONG AND SOUTH OF I-16 AS SHOWERS AND THUNDERSTORMS
PASS.
TONIGHT: AFTERNOON SHOWERS AND THUNDERSTORMS ARE EXPECTED TO
PUSH OFFSHORE BY THE EARLY EVENING AND FROM THEN ON THERE ISN'T
A TON OF CONFIDENCE IN HOW SHOWER POTENTIAL WILL WORK OUT
OVERNIGHT. WE WILL REMAIN LARGELY DEVOID OF ANY LARGE SCALE
FORCING, THOUGH THERE ARE SOME SUGGESTIONS THAT SUBTLE SHORTWAVE
ENERGY WILL PASS THROUGH WITHIN THE WESTERLY FLOW. THE ILL-
DEFINED SURFACE BOUNDARY IS EXPECTED TO BE ALIGNED SOUTH OF THE
AREA NEAR THE FL STATE LINE. SO, THE FORECAST ALLOWS FOR RAIN
CHANCES TO END IN THE EVENING BUT WE DO ALLOW 20 PERCENT CHANCES
TO COME BACK IN LATE TO ACCOUNT FOR POSSIBLE ISOLATED SHOWER
DEVELOPMENT WITHIN THE WARM AND MOIST ENVIRONMENT. LOWS ARE
FORECAST TO BE IN THE UPPER 50S TO LOW 60S INLAND, AND THE MID
60S ALONG THE COAST.
SHORT TERM /THURSDAY THROUGH SATURDAY/
THURSDAY: AS AN UPPER-LVL LOW SITUATED OVER THE MID-MISSISSIPPI
VALLEY APPROACHES THE REGION, THE ALMOST STATIONARY FRONT WILL
CONTINUE TO LINGER NEARBY. COMPARED TO THE PAST WEEK OF
GUIDANCE, THIS PATTERN HAS BEEN MORE SLOW TO PROGRESS AND MAY
SUPPORT ADDITIONAL RAINFALL IF THIS TREND CONTINUES OVER THE
NEXT COUPLE DAYS. WHILE GFS/CMC POINT TO A RATHER DRY FORECAST
TODAY, ALL OTHER GUIDANCE SUGGESTS OTHERWISE. EXPECT SHOWERS AND
THUNDERSTORMS TO DEVELOP IN THE MORNING (~12-13Z) ACROSS
SOUTHEAST GEORGIA AND EVENTUALLY INTO SOUTHEAST SOUTH CAROLINA
IN THE EARLY AFTERNOON (~18- 19Z). LOCATED ON THE COOLER SIDE OF
THE UPPER-LVL LOW, INSTABILITY REMAINS QUITE LIMITED THROUGHOUT
THE DAY WITH SBCAPE VALUES MOSTLY WAVERING ~1000 J/KG. HOWEVER
HEADING INTO THE AFTERNOON, SRH VALUES BECOME MORE IMPRESSIVE
AND THE POTENTIAL TO SEE SOME ORGANIZED THUNDERSTORMS IS NOT
TOTALLY OFF THE TABLE. WITH A FRONTAL BOUNDARY PUSHING OFFSHORE
IN THE EVENING, MOST OF THE SHOWERS AND THUNDERSTORMS WILL SHIFT
OVER THE WATERS. ADDITIONALLY, WPC HAS HIGHLIGHTED SOUTHEAST
GEORGIA IN A MARGINAL RISK AS THIS AREA WILL MOST LIKELY SEE THE
MOST RAINFALL (~0.25-0.50"). SOUTHEASTERLY WINDS COULD BECOME
QUITE GUSTY ALONG THE COASTLINE IN THE EVENING WITH THE
SEABREEZE AND THE FRONT SHIFTING OFFSHORE. DESPITE THE LACK OF
SUN, HIGHS WILL CLIMB 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: AS THIS UPPER-LVL LOW SITUATES ITSELF IN THE DEEP
SOUTH, AN ASSOCIATED COLD FRONT WILL PASS THROUGH THE REGION
THROUGHOUT THE DAY. A GOOD AMOUNT OF GUIDANCE INDICATES THAT
THIS LOW WILL YIELD NUMEROUS SHOWERS AND THUNDERSTORMS
THROUGHOUT THE DAY. ADDITIONALLY, WPC HAS HIGHLIGHTED THE ENTIRE
REGION UNDER A MARGINAL RISK FOR EXCESSIVE RAINFALL. WITH PWAT
VALUES RANGING ~1.50-2.00 INCHES AND EXTREMELY MOIST
SOUTHWESTERLY FLOW BEING ADVECTED INTO THE REGION, DECENT
AMOUNTS OF RAINFALL COULD BE SEEN. RAINFALL AMOUNTS FOR FRIDAY
RANGE FROM 0.75 TO 1.25 INCHES, WITH MOST PRECIPITATION FALLING
IN SOUTHEAST GEORGIA AGAIN. EXPECT TEMPERATURES TO BE NEAR
NORMAL ON FRIDAY.
SATURDAY: THIS UPPER-LVL LOW WILL ALMOST PARK ITSELF ACROSS THE
GULF STATES AND CONTINUE TO PUSH RICH MOISTURE INTO THE
SOUTHEAST. EXPECT SHOWERS AND THUNDERSTORMS TO CONTINUE
THROUGHOUT THE DAY. WPC HIGHLIGHTED THE ENTIRE REGION UNDER A
MARGINAL RISK FOR EXCESSIVE RAINFALL AGAIN. THIS APPEARS TO THE
HEAVIEST DAY OF RAINFALL WITH PRECIPITATION AMOUNTS RANGING FROM
1.0 TO 1.50 INCHES. DUE TO THE RELATIVELY DRY ANTECEDENT
CONDITIONS, THE OVERALL FLASH FLOODING POTENTIAL REMAINS ON THE
LOWER SIDE. GIVEN THE OVERALL PATTERN, TEMPERATURES WILL BE
BELOW NORMAL FOR THIS TIME OF YEAR WITH HIGHS ONLY REACHING INTO
THE LOW TO MID 70S WITH POCKETS OF UPPER 70S IN SOUTHEAST
GEORGIA. NORTHEASTERLY WINDS WILL LIKELY BECOME GUSTY AGAIN IN
THE EVENING (MAINLY ALONG THE COASTLINE) AS THE AFOREMENTIONED
FRONTAL BOUNDARY LINGERS NEARBY.
LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/
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. WITH DEEP TROPICAL MOISTURE POOLING IN
FROM THE GULF, THIS PATTERN WILL SUPPORT DAILY HEAVY RAINFALL
THREATS INTO EARLY NEXT WEEK. THERE IS POTENTIAL TO SEE RAINFALL
AMOUNTS OF 2+ INCHES IN SOME SPOTS. EVENTUALLY THIS CLOSED LOW
WILL BEGIN TO SLOWLY SHIFT NORTHEASTWARD AND PLACE THE REGION IN
FAVORABLE LOCATION FOR STRONG UPPER-LVL DIVERGENCE. MULTIPLE
ROUNDS OF POTENTIALLY HEAVY SHOWERS AND THUNDERSTORMS WILL PASS
THROUGH THIS PERIOD AND ALLOW FOR SOME VERY NEEDED RAINFALL.
THIS SETUP WILL INDUCE NEAR AND BELOW NORMAL TEMPERATURES.
AVIATION /07Z WEDNESDAY THROUGH SUNDAY/
KCHS AND KJZI: THE FIRST FORECAST CONCERN IS FOR POTENTIAL FOG
DEVELOPMENT IN THE NEXT FEW HOURS. WE HAVE INTRODUCED A TEMPO
GROUP AT BOTH SITES TO ADVERTISE MVFR FOG, BUT IT ISN'T
COMPLETELY OUT OF THE QUESTION FOR IFR VISIBILITIES. THE MAIN
TIME PERIOD IS FROM ROUGHLY 08-12Z. THEN AS WE LOOK LATER IN THE
DAY THERE WILL BE THE POTENTIAL FOR SHOWERS TO MOVE THROUGH IN
THE EARLY TO MID AFTERNOON HOURS. MODEL GUIDANCE GENERALLY
HIGHLIGHTS THE MAIN TIME PERIOD OF CONCERN FROM 18-22Z AND WE
ARE CARRYING VCSH. THERE REMAINS ENOUGH UNCERTAINTY REGARDING
THE POTENTIAL FOR THE SITES TO BE DIRECTLY IMPACTED, SO FURTHER
REFINEMENTS WILL LIKELY BE NEEDED WITH THE 12Z TAF ISSUANCE. IF
SHOWERS DO DIRECTLY IMPACT THE TERMINALS, BRIEF PERIODS OF MVFR
CONDITIONS WILL BE POSSIBLE.
KSAV: THE FIRST FORECAST CONCERN IS FOR POTENTIAL FOG
DEVELOPMENT IN THE NEXT FEW HOURS. CURRENT THINKING IS THAT THE
FOG WILL MAINLY BE SHALLOW WITH NO REDUCTION IN FLIGHT CATEGORY.
ATTENTION THEN TURNS TO THE POTENTIAL FOR SHOWERS AND
THUNDERSTORMS STARTING AROUND MIDDAY. THE COMBINATION OF THE
ARRIVAL OF A DIMINISHING AREA OF SHOWERS AND THUNDERSTORMS FROM
THE WEST INTERACTING WITH THE SEA BREEZE ALONG THE GA COAST
SHOULD PRODUCE AN AREA OF SHOWERS AND THUNDERSTORMS NEAR THE
TERMINAL. AS SUCH, WE BRING IN VCSH AT 16Z AND HAVE A TEMPO
GROUP FROM 16-20Z TO ACCOUNT FOR DIRECT IMPACTS BRINGING THE
FLIGHT CATEGORY DOWN INTO THE MVFR RANGE. THUNDERSTORMS ARE
STILL POSSIBLE, BUT WE AREN'T QUITE CONFIDENT ENOUGH YET TO PUT
TSRA INTO THE TAF. ONCE THIS SHOWER AND THUNDERSTORM ACTIVITY
MOVES OFF TO THE EAST BY THE MID AFTERNOON, VFR CONDITIONS
SHOULD PREVAIL.
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: THE LOCAL WATERS WILL REMAIN WITHIN A
WEAK PRESSURE GRADIENT THROUGH THE PERIOD WHICH WILL KEEP WINDS
AND SEAS WELL BELOW SMALL CRAFT ADVISORY THRESHOLDS. WINDS THIS
MORNING WILL BE LIGHT AND VARIABLE BEFORE BECOMING ONSHORE 5-10
KNOTS IN THE AFTERNOON. OVERNIGHT, LIGHT SOUTHERLY FLOW SHOULD
CONTINUE WITH SPEEDS NO MORE THAN 5-10 KNOTS. SEAS SHOULD
AVERAGE AROUND 2 FEET THROUGH THE PERIOD.
FRIDAY THROUGH MONDAY: AS THIS UPPER-LVL LOW APPROACHES THE
REGION OVER THE NEXT COUPLE DAYS, A NEARBY STATIONARY FRONT AT
THE SURFACE WILL FLUCTUATE BACK AND FORTH OVER THE ATLANTIC
WATERS. THIS WILL SUPPORT UNSETTLED WEATHER CONDITIONS AND
SHOWERS AND THUNDERSTORMS COULD POSSIBLE EACH DAY. HOWEVER,
CONDITIONS SHOULD REMAIN UNDER SMALL CRAFT ADVISORY CRITERIA. IN
GENERAL, OFFSHORE WINDS WILL PEAK ~10 TO 15 KT WITH GUSTS (~20
KT) BECOMING SLIGHTLY STRONGER WITH THE SEA BREEZE EACH EVENING.
THANKS TO WINDS IN THE TROPICAL EASTERLIES, EASTERLY SWELL
SHOULD BE ON TAP AND ALLOW FOR SOME GOOD SURF TO DEVELOP. SEAS
WILL BE FROM 2 TO 4 FT OVER THE WEEKEND AND THEN BECOMING 4 TO 5
FT ON MONDAY.
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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