041
FXUS62 KCHS 200555
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
155 AM EDT WED MAY 20 2026
WHAT HAS CHANGED
ALL KEY MESSAGES AND SECTIONS WERE UPDATED.
KEY MESSAGES
- 1) AREAS OF FOG, LOCALLY DENSE, ARE POSSIBLE ACROSS THE SOUTH
CAROLINA LOWCOUNTRY AND SOUTHEAST GEORGIA THIS MORNING.
- 2) RAIN CHANCES LIKELY TO INCREASE LATE IN THE WEEK, THOUGH
NO HAZARDOUS WEATHER IS ANTICIPATED AT THIS TIME.
DISCUSSION
KEY MESSAGE 1: AREAS OF FOG, LOCALLY DENSE, ARE POSSIBLE ACROSS
THE SOUTH CAROLINA LOWCOUNTRY AND SOUTHEAST GEORGIA THIS
MORNING.
LOW-LEVEL MOISTURE APPEARS TO BE A TAD DEEPER COMPARED TO THE
PAST FEW MORNINGS WITH HIGHER 1000 HPA CONDENSATION PRESSURE
DEFICITS NOTED. THE RISK FOR SHALLOW FOG WILL INCREASE OVER THE
NEXT FEW HOURS AS THE BOUNDARY LAYER DECOUPLES AND RADIATIONAL
COOLING MAXIMIZES. WITH SLIGHTLY FAVORABLE FOG PARAMETERS IN
PLACE, SHALLOW FOG LAYERS COULD THICKEN A BIT MORE THAN WHAT
HAS BEEN EXPERIENCED OVER THE PAST FEW MORNINGS RESULTING IN A
BIT MORE IN THE WAY OF MEANINGFUL FOG AND LOWER VISIBILITIES.
THE FOG THAT DOES FORM COULD BE LOCALLY DENSE AT TIMES WITH
VISIBILITIES DROPPING TO 1/4 NM OR LESS AT TIMES, ESPECIALLY
NEAR BODIES OF WATER AND OTHER LOW-LYING AREAS SUCH AS MARSHES,
SWAMPS AND LARGE DITCHES. THE AREA FROM REIDSVILLE TO TOWNSEND
NORTH TO HAMPTON, BEAUFORT AND WALTERBORO, INCLUDING PARTS OF
THE SAVANNAH METRO AREA, LOOKS TO BE THE CORRIDOR OF MOST
CONCERN FOR MORE MEANINGFUL FOG DEVELOPMENT THROUGH DAYBREAK.
THE NEED FOR A SPECIAL WEATHER STATEMENT OR EVEN A DENSE FOG
ADVISORY WILL BE REASSESSED AS THE EARLY MORNING PROGRESSES.
KEY MESSAGE 2: RAIN CHANCES LIKELY TO INCREASE LATE IN THE
WEEK, THOUGH NO HAZARDOUS WEATHER IS ANTICIPATED AT THIS TIME.
THE AREA WILL REMAIN ALONG THE WESTERN FLANKS OF ATLANTIC HIGH
PRESSURE CENTERED WELL OFFSHORE. EARLY MORNING WATER VAPOR
IMAGERY SHOWS A WELL DEFINED TROPICAL UPPER TROPOSPHERIC TROUGH
(TUTT) LOW POSITIONED NEAR 29N/75W AT 20/06Z. BROAD SUBSIDENCE
ALOFT ALONG THE WESTERN FLANKS OF THE TUTT WILL CONTINUE TO
RESIDE OVER THE AREA THROUGH TONIGHT WITH SUBTROPICAL RIDGING
PROGGED TO HOLD ALOFT ACROSS MUCH OF THE SOUTHEAST STATES. THE
TUTT IS FORECAST TO SLOWLY WEAKEN AND REMAIN WELL OFFSHORE AS
THE IT PROPAGATES WEST/NORTHWEST ALONG THE BACKSIDE OF THE
SUBTROPICAL ANTICYCLONE MEANDERING NEAR BERMUDA. THE NET RESULT
WILL BE A CONTINUATION OF WARM, RAIN-FREE CONDITIONS WITH SOME
HIGH CLOUDS SPREADING IN AT TIMES.
LOW-LEVEL THICKNESSES ARE PROGGED TO MAX OUT ABOUT 10-30 METERS
HIGHER THAN TUESDAY AS SUBSIDENCE ALOFT BUILDS. HIGHS ARE POISED
TO WARM INTO THE LOWER-MID 90S INLAND WITH UPPER 70S/NEAR 80 AT
THE BEACHES. TEMPERATURES ACROSS THE COASTAL COUNTIES WILL
REMAIN WHAT SOMEWHAT TEMPERED AS ANOTHER ROBUST, PURE SEA BREEZE
CIRCULATION PROPAGATES STEADILY INLAND THROUGH THE AFTERNOON.
SIMILAR TO THE PAST FEW NIGHTS, IT WILL TAKE UNTIL THE EARLY
MORNING HOURS THURSDAY BEFORE THE BOUNDARY FULLY DECOUPLES AND
INFLUENCES FROM THE AFTERNOON SEA BREEZE WANE. LOWS WILL RANGE
FROM THE MID 60S INLAND TO THE LOWER 70S AT THE BEACHES. LOW-
LEVEL MOISTURE PROFILES AND 1000 HPA CONDENSATION PRESSURE
DEFICITS DO NOT LOOK AS FAVORABLE FOR FOG DEVELOPMENT COMPARED
TO THIS MORNING, BUT SOME SHALLOW GROUND FOG APPEARS LIKELY,
ESPECIALLY AWAY FROM THE IMMEDIATE COAST.
UPPER LEVEL RIDGING LINGERS ACROSS THE SOUTHEASTERN CONUS
THURSDAY, AS A SFC COLD FRONT STALLS OUT ALONG THE TENNESSEE
RIVER VALLEY. AS SUCH, SHOULD SEE LARGELY DRY CONDITIONS PREVAIL
ACROSS OUR AREA, WITH HIGHS FORECAST TO RISE INTO THE LOWER 90S
UNDER MOSTLY SUNNY SKIES.
WILL SEE THE AFOREMENTIONED COLD FRONT SAG SOUTHWARD OVER THE
CAROLINAS BY FRIDAY, CAUSING THE UPPER LEVEL RIDGE TO SHIFT OVER
THE ATLANTIC. WHILE THE EXACT POSITION OF THE FRONT AND HOW FAR
SOUTH IT PROGRESSES WILL BE THE KEY FACTOR IN DETERMINING
RAINFALL COVERAGE AND AMOUNTS, CURRENT TRENDS CONTINUE TO FAVOR
A STRONG ATLANTIC RIDGE. THIS WOULD KEEP THE FRONT DISPLACED
JUST TO OUR WEST AND NORTH, AND THUS LIMIT OUR CHANCES FOR
SEEING MEANINGFUL RAINFALL. ENSEMBLE GUIDANCE CONTINUES TO
FOLLOW THIS TREND AS WELL, WITH PROBABILITIES FOR SEEING
RAINFALL GREATER THAN AN INCH THROUGH SATURDAY REMAINING LESS
THAN 25%. SO, WHILE TRENDS CURRENTLY FAVOR A DRIER, LESS
IMPACTFUL EVENT, STILL ENCOURAGE FOLKS TO MONITOR THE LATEST
FORECAST AS SUBTLE SHIFTS IN TRACK MAY STILL OCCUR. OTHERWISE,
EXPECT THE SEVERE POTENTIAL WITH ANY SHOWER/STORM TO REMAIN LOW,
GIVEN THE LACK OF FORCING AND MOISTURE IN PLACE.
AVIATION /06Z WEDNESDAY THROUGH SUNDAY/
20/06Z TAF DISCUSSION:
KCHS/JZI: THE RISK FOR FOG WILL INCREASE THROUGH DAYBREAK. IT IS
NOT EXACTLY CLEAR HOW SIGNIFICANT ANY FOG WILL BECOME WITH THE
BETTER FOG PARAMETERS FORECAST TO REMAIN WEST AND SOUTHWEST OF
BOTH TERMINALS; HOWEVER, GUIDANCE IS TRENDING LOWER WITH VSBYS
AND THE 06Z TAFS WILL REFLECT THIS TREND. PREVAILING VSBYS WERE
LIMITED TO LOW-END MVFR AT BOTH TERMINALS WITH TEMPO GROUPS
DROPPING RIGHT TO ALTERNATE MINIMUMS AT KCHS AND JUST BELOW
ALTERNATE MINIMUMS AT KJZI. THE FOG WILL LIKELY REMAIN SOMEWHAT
SHALLOW SO CIG ESTABLISHMENT IS NOT EXPECTED. THE FOG WILL
QUICKLY MIX OUT AFTER DAYBREAK WITH CONDITIONS QUICKLY RETURNING
TO VFR BY 13Z. VFR WILL THEN PREVAIL FOR THE REMAINDER OF THE
06Z TAF PERIOD.
KSAV: THE RISK FOR FOG WILL INCREASE THROUGH DAYBREAK. THE
TERMINAL LOOKS TO BE POSITIONED THE AREA OF MOST FAVORABLE FOG
PARAMETERS, BUT IT REMAINS UNCLEAR HOW LOW VSBYS WILL GO GIVEN
LOW-LEVEL MOISTURE STILL REMAINS FAIRLY SHALLOW. EXPECT MVFR
VSBYS BY 09Z WITH PREVAILING CONDITIONS DROPPING TO ALTERNATE
MINIMUMS BY 10Z. OPTED FOR A TEMPO GROUP FOR 1/2SM BR BKN003
WITH THE ANTICIPATION OF SOME POCKETS OF DENSE FOG OCCURRING.
THE FOG WILL QUICKLY MIX OUT AFTER DAYBREAK WITH CONDITIONS
QUICKLY RETURNING TO VFR BY 13Z. VFR WILL THEN PREVAIL FOR THE
REMAINDER OF THE 06Z TAF PERIOD.
EXTENDED AVIATION OUTLOOK: THERE ARE NO HIGH CONFIDENCE
CONCERNS.
MARINE
THROUGH TONIGHT: QUIET CONDITIONS WILL PERSIST WITH THE REGION
POSITIONED ALONG THE WESTERN FLANKS OF ATLANTIC HIGH PRESSURE
CENTERED WELL OFFSHORE. EAST/SOUTHEAST WINDS WILL PREVAIL WITH
SPEEDS LESS THAN 15 KT, ALTHOUGH SOME LOCAL ENHANCEMENT ALONG
THE LAND/SEA INTERFACE AND CHARLESTON HARBOR WILL LIKELY OCCUR
WITH THE SEA BREEZE. SEAS WILL AVERAGE 2-4 FT.
THURSDAY THROUGH SUNDAY: NO MARINE CONCERNS ARE EXPECTED. HIGH
PRESSURE TO THE EAST WILL DRIVE ONSHORE EAST-SOUTHEASTERLY FLOW
EACH DAY, WITH WIND SPEEDS MOSTLY TOPPING OUT IN THE 10-15 KNOT
RANGE. EACH AFTERNOON AND EVENING THERE COULD BE SOME LOCAL
ENHANCEMENT ALONG THE LAND/SEA INTERFACE WITH THE DIURNAL SEA
BREEZE. SEAS WILL AVERAGE 2-4 FEET THROUGH THE PERIOD.
RIP CURRENTS: A LINGERING 9 SEC, 2-3 FT SWELL WILL KEEP A
MODERATE RIP CURRENT RISK IN PLACE FOR ALL BEACHES THROUGH THIS
EVENING.
CHS WATCHES/WARNINGS/ADVISORIES
GA...NONE.
SC...NONE.
MARINE...NONE.
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