251
FXUS62 KCHS 170908
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
508 AM EDT WED SEP 17 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/
A DEEP, CYCLONIC FLOW AROUND THE NEARLY VERTICALLY STACKED
CYCLONE CENTERED OVER THE VIRGINIA TIDEWATER AND DELMARVA WILL
REMAIN IN PLACE ACROSS THE SOUTHEAST U.S. THROUGH TONIGHT. ANY
DIRECT IMPACTS FROM THIS SYSTEM WILL REMAIN DISPLACED WELL TO
THE NORTH WITH SURFACE HIGH PRESSURE HOLDING ACROSS THE SOUTH
CAROLINA LOWCOUNTRY AND SOUTHEAST GEORGIA. MODELS SHOW A FEW
WEAK MID-LEVEL PERTURBATIONS ROUNDING THE BASE OF THE UPPER LOW
AND PROPAGATING ACROSS CENTRAL GEORGIA LATER THIS AFTERNOON.
THERE MAY BE JUST ENOUGH FORCING AND MARGINAL MID-LEVEL MOISTURE
WITH THIS FEATURE TO SUPPORT AN ISOLATED SHOWER OR TWO ACROSS
INTERIOR SOUTHEAST GEORGIA INTO PARTS OF ALLENDALE, HAMPTON AND
COLLETON COUNTIES IN THE LOWCOUNTRY, BUT THIS SIGNAL IS PRETTY
WEAK WITH THE 17/00Z HREF SHOWING PROBABILITIES OF >0.01"
RUNNING 15% OR LESS, HREF 25-75% PERCENTILE 6-HR QPF BOTH AT
0.00" AND 17/01Z NBM MEAN 6-HR QPF ONLY SHOWING VERY TINY
SPLOTCHES OF >0.01". A DRY MEAN WEST/NORTHWEST FLOW IN THE
925-700 HPA LAYER FORECAST TO PREVAIL TODAY, SO THE SET UP DOES
NOT APPEAR ALL THAT FAVORABLE FOR MEASURABLE RAINFALL. POPS WERE
HELD BELOW MENTIONABLE THRESHOLDS FOR THIS REASON, RANGING FROM
10% ACROSS INTERIOR SOUTHEAST GEORGIA TO 5% OR LESS ELSEWHERE.
RAIN-FREE CONDITIONS WILL LINGER INTO TONIGHT.
HIGHS THIS AFTERNOON WILL WARM IN THE UPPER 80S/NEAR 90 WEST OF
I-95, MID-UPPER 80S ACROSS THE COASTAL CORRIDOR WITH LOWER 80S
AT THE BEACHES. THE BOUNDARY LAYER IS LIKELY TO DECOUPLE AGAIN
AFTER SUNSET, BUT THICKENING HIGH CLOUDS WITH ORIGINS FROM THE
WESTERN CARIBBEAN WILL LIKELY LIMIT RADIATIONAL COOLING
SOMEWHAT. LOWS WILL RANGE FROM THE MID 60S INLAND TO THE MID 70S
AT THE BEACHES. A FEW POCKETS OF LOWER 60S COULD OCCUR ACROSS
THE INTERIOR, MAINLY THE TYPICAL, MORE SHELTERED LOCATIONS SUCH
AS THE FRANCIS MARION NATIONAL FOREST.
SHORT TERM /THURSDAY THROUGH SATURDAY/
MID LEVEL TROUGH EXTENDING OVER THE SOUTHEAST AT THE START OF
THE PERIOD WILL EVENTUALLY LIFT AND SHIFT TO THE EAST, ALLOWING
HEIGHTS TO RISE. THE SURFACE WILL LARGELY FEATURE WEAK HIGH
PRESSURE, BEFORE STRONGER HIGH PRESSURE BUILDS IN FROM THE NORTH
OVER THE WEEKEND. QUIET WEATHER WILL PERSIST WITH THE
PROBABILITY FOR RAINFALL LESS THAN 15% THROUGH SATURDAY.
TEMPERATURES WILL TREND ON THE WARMER SIDE OF NORMAL, WITH HIGHS
EXPECTED TO PEAK IN THE UPPER 80S TO AROUND 90 IN MOST
LOCATIONS AWAY FROM THE IMMEDIATE COAST. LOWS WILL MAINLY BE IN
THE 65-70 RANGE.
LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/
A RIDGE OF HIGH PRESSURE WILL EXTEND SOUTH INTO THE REGION
THROUGH AT LEAST MONDAY, WHILE A COASTAL TROUGH DEVELOPS
OFFSHORE. THE TROUGH COULD EVENTUALLY SHIFT ONSHORE ON TUESDAY.
ALOFT, THE FORECAST AREA WILL BECOME INCREASINGLY POSITIONED
BETWEEN A RIDGE WELL OFFSHORE AND A TROUGH APPROACHING FROM THE
WEST. DEEPER MOISTURE WILL SPREAD INTO THE AREA AND WITH SOME
HINTS OF SHORTWAVE ENERGY ROTATING NEARBY, LOW-END RAIN CHANCES
(GENERALLY 20-30%) RETURN TO THE FORECAST. TEMPERATURES ARE
EXPECTED TO BE NEAR OR SLIGHTLY BELOW NORMAL.
AVIATION /09Z WEDNESDAY THROUGH SUNDAY/
17/12Z TAFS:
KCHS/KJZI/KSAV: VFR WILL PREVAIL THROUGH 18/12Z.
EXTENDED AVIATION FORECAST: EXTENDED AVIATION FORECAST: VFR IS
EXPECTED THROUGH SATURDAY. GUSTY NORTHEASTERLY WINDS (15-20 KT)
ARE POSSIBLE WITH A WEDGE OF HIGH PRESSURE SATURDAY AND SUNDAY.
BRIEF FLIGHT RESTRICTIONS ARE ALSO POSSIBLE WITH SHOWERS ON
SUNDAY.
MARINE
THOUGH TONIGHT: OFFSHORE WINDS WILL BACK MORE THE SOUTH AND
SOUTHWEST THIS AFTERNOON AS A SEA BREEZE DEVELOPS. WINDS WILL
SURGE NEAR THE SEA BREEZE, BUT SPEEDS SHOULD GENERALLY PEAK NO
HIGHER THAN 10 KT. SOUTH TO SOUTHWEST WINDS WILL LINGERING INTO
TONIGHT WITH SPEEDS GENERALLY AROUND 10 KT. SEAS WILL AVERAGE
1-3 FT.
THURSDAY THROUGH MONDAY: RELATIVELY BENIGN MARINE CONDITIONS
ARE EXPECTED THROUGH FRIDAY WITH WINDS 15 KNOTS OR LESS AND SEAS
1-3 FEET. THE PRESSURE GRADIENT WILL TIGHTEN OVER THE WEEKEND
AS HIGH PRESSURE RIDGES SOUTH INTO THE REGION AND A COASTAL
TROUGH DEVELOPS OFFSHORE. THIS WILL LEAD TO INCREASING SEAS AND
GUSTY NORTHEAST WINDS. CONDITIONS COULD APPROACH SMALL CRAFT
ADVISORY CRITERIA FOR AT LEAST PORTIONS OF THE WATERS.
EQUIPMENT
THE KCLX RADAR REMAINS OFFLINE THROUGH SEPTEMBER 18 DUE TO
HARDWARE UPGRADES. USERS ARE ENCOURAGED TO USE ADJACENT WSR-88D
RADAR SITES. THESE RADARS INCLUDE:
KCAE: COLUMBIA, SC
KLTX: WILMINGTON, NC
KJAX: JACKSONVILLE, FL
KVAX: MOODY AIR FORCE BASE, GA
KJGX: ROBBINS AIR FORCE BASE, GA:
CHS WATCHES/WARNINGS/ADVISORIES
GA...NONE.
SC...NONE.
MARINE...NONE.
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