830
FXUS62 KCHS 180527
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
127 AM EDT THU SEP 18 2025
SYNOPSIS
WEAK HIGH PRESSURE WILL EXTEND ACROSS THE REGION THIS WEEK.
STRONGER HIGH PRESSURE WILL BUILD INTO THE REGION OVER THE
WEEKEND AND EARLY NEXT WEEK, WHILE A COASTAL TROUGH DEVELOPS
OFFSHORE.
NEAR TERM /THROUGH TONIGHT/
THE SYNOPTIC PATTERN ACROSS THE SOUTHEAST U.S. HAS CHANGED
LITTLE SINCE WEDNESDAY WITH A BROAD, CYCLONIC FLOW FORECAST TOLD
HOLD THROUGH TONIGHT EVEN AS THE WEAKENING UPPER LOW OVER THE
DELMARVA CONTINUES TO OPEN UP AND KICKS OUT ACROSS NEW ENGLAND.
WEAK SURFACE HIGH PRESSURE WILL MAINTAIN ITS INFLUENCE ON THE
REGION, BUT SIMILAR TO WEDNESDAY, WEAK PERTURBATIONS MOVING
THROUGH THROUGH THE BASE OF THE UPPER TROUGH ARE FORECAST TO
PROPAGATE ACROSS CENTRAL GEORGIA INTO PARTS OF SOUTHEAST GEORGIA
LATER THIS AFTERNOON. NET MOISTURE VALUES WILL INCREASE SLIGHTLY
THROUGH THE DAY WITH A BIT MORE MID-LEVEL RH AND HIGHER PWATS
(~1.35-1.50") NOTED. RAP SOUNDINGS SHOW AS MUCH AS 1000-1500
J/KG OF MLCAPE DEVELOPING BY MID-AFTERNOON, BUT THERE IS SOME
CONCERN THE MIXING OUT OF DEWPOINTS INLAND AHEAD OF THE
AFTERNOON SEA BREEZE MAY LIMIT NET INSTABILITY SOMEWHAT. THERE
STILL LOOKS TO BE ENOUGH FORCING AND MOISTURE FOR ISOLATED TO
SCATTERED SHOWERS/TSTMS TO DEVELOP THIS AFTERNOON, MOSTLY WEST
OF I-95 WHERE THE HIGHER 850 HPA THETA-E VALUES ARE PROGGED.
THIS IS CONSISTENT WITH SIMULATED REFLECTIVITY OFF A NUMBER OF
THE CAMS. POPS OF 20-30% WERE INTRODUCED ROUGHLY ALONG/WEST OF
I-95 TO ACCOUNT FOR THIS ACTIVITY, MAINLY FROM MID-AFTERNOON
THROUGH SUNSET. RAIN CHANCES WILL QUICKLY DIMINISH THIS EVENING
WITH RAIN FREE CONDITIONS PREVAILING FOR THE OVERNIGHT HOURS.
HIGHS THIS AFTERNOON WILL RANGE FROM THE UPPER 80S/LOWER 90S
WEST OF I-95 TO THE MID-UPPER 80S ACROSS THE COASTAL CORRIDOR
WITH LOWER-MID 80S AT THE BEACHES. OVERNIGHT LOWS WILL RANGE
FROM THE MID-UPPER 60S INLAND TO THE MID 70S AT THE BEACHES.
SHORT TERM /FRIDAY THROUGH SUNDAY/
A WEAK PRESSURE PATTERN WILL BE IN PLACE AT THE SURFACE ON
FRIDAY. OVER THE WEEKEND, STRONG HIGH PRESSURE WILL BUILD IN
FROM THE NORTH, WHILE A COASTAL TROUGH, OR PERHAPS EVEN A WEAK
LOW, TAKES SHAPE OFFSHORE. THE FORECAST IS LARGELY DRY, BUT
COULD NOT RULE OUT A FEW SHOWERS BRUSHING COASTAL AREAS
ESPECIALLY DURING THE LATTER HALF OF THE PERIOD WHERE 20% POPS
ARE HIGHLIGHTED. HIGH TEMPERATURES ARE FORECAST TO BE IN THE
85-90F RANGE OVER MOST LOCATIONS INLAND OF THE IMMEDIATE COAST,
WARMEST ON FRIDAY. LOWS WILL AVERAGE IN THE MID TO UPPER 60S.
LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/
BROAD MID LEVEL TROUGHING WILL SHIFT TOWARDS THE EASTERN U.S.
EARLY NEXT WEEK. A STRONGER WAVE COULD FOLLOW MIDWEEK, BUT STILL
LACKING SOME CONSISTENCY BETWEEN GLOBAL MODELS. AT THE SURFACE,
HIGH PRESSURE WILL LIKELY PERSIST, WITH HINTS THAT THE
AFOREMENTIONED COASTAL TROUGH COULD SHIFT ONSHORE BEFORE
EVENTUALLY DISSIPATING. RAIN CHANCES REMAIN NO HIGHER THAN
20-30% GIVEN DECENT SPREAD IN SOLUTIONS. TEMPERATURES COULD WARM
BACK UP TOWARDS THE MIDDLE OF THE WEEK.
AVIATION /06Z THURSDAY THROUGH MONDAY/
18/06Z TAFS:
KCHS/KJZI/KSAV: VFR WILL PREVAIL THROUGH 19/06Z. ISOLATED TO
SCATTERED SHOWERS/TSTMS ARE EXPECTED TO REMAIN WEST OF I-95 THIS
AFTERNOON. SOME OF THIS ACTIVITY COULD APPROACH KSAV BY LATE
AFTERNOON. CONFIDENCE IS TOO LOW TO JUSTIFY A MENTION AT THIS
TIME, BUT THIS WILL BE REVISITED FOR THE 12Z TAFS PENDING
ADDITIONAL MODEL RUNS.
EXTENDED AVIATION FORECAST: VFR IS EXPECTED THROUGH SATURDAY.
GUSTY NORTHEASTERLY WINDS (15-20 KT) ARE POSSIBLE WITH A WEDGE
OF HIGH PRESSURE EACH AFTERNOON SATURDAY THROUGH MONDAY. BRIEF
FLIGHT RESTRICTIONS ARE ALSO POSSIBLE WITH SHOWERS AND LOW
CLOUDS SUNDAY AND MONDAY.
MARINE
THROUGH TONIGHT: SOUTHERLY WINDS WILL INCREASE AND BACK NEAR
THE LAND/SEA INTERFACE AND CHARLESTON HARBOR THIS AFTERNOON WITH
DEVELOPMENT OF A ROBUST SEA BREEZE CIRCULATION. WINDS AS HIGH
15 KT WITH GUSTS TO 20 KT ARE EXPECTED WITHIN THE CIRCULATION
ITSELF WITH WINDS AROUND 10 KT WITH GUSTS TO 15 KT ELSEWHERE.
SOUTHEAST WINDS WILL BECOME MORE NORTHERLY OVERNIGHT AS INLAND
AREAS COOL. SPEEDS WILL REMAIN LESS THAN 10 KT. SEAS WILL
AVERAGE 1-3 FT THROUGH THE PERIOD.
FRIDAY THROUGH TUESDAY: MAIN TIME PERIOD OF CONCERN IS OVER THE
WEEKEND INTO EARLY NEXT WEEK AS STRONG HIGH PRESSURE BUILDS
INLAND AND A COASTAL TROUGH SHARPENS OFFSHORE. A TIGHT PRESSURE
GRADIENT BETWEEN THESE TWO FEATURES WILL LEAD TO GUSTY NORTHEAST
WINDS AND BUILDING SEAS. CONDITIONS COULD SUPPORT SMALL CRAFT
ADVISORIES FOR PORTIONS OF THE WATERS. THERE SHOULD BE
IMPROVEMENT LATER MONDAY AND ESPECIALLY TUESDAY.
CHS WATCHES/WARNINGS/ADVISORIES
GA...NONE.
SC...NONE.
MARINE...NONE.
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