176  
FXUS62 KCHS 230547  
AFDCHS  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE CHARLESTON SC  
147 AM EDT THU OCT 23 2025  
   
SYNOPSIS  
 
HIGH PRESSURE WILL PREVAIL THROUGH THE WEEKEND, THEN AN UPPER  
DISTURBANCE WILL MOVE THROUGH EARLY NEXT WEEK. A STRONG COLD  
FRONT COULD MOVE THROUGH DURING THE MIDDLE OF NEXT WEEK.  
 
 
   
NEAR TERM /THROUGH TONIGHT/  
 
THROUGH DAYBREAK: THE BOUNDARY LAYER HAS DECOUPLED IN MOST SPOTS  
EARLY THIS MORNING WITH CALM/LIGHT WINDS BEING REPORTED. SKIES  
ARE CLEAR, ALTHOUGH A FEW WISPS OF CIRRUS COULD BRUSH PARTS OF  
SOUTHEAST GEORGIA CLOSER TO DAYBREAK. STRONG RADIATIONAL COOLING  
WILL PERSIST WITH LOWS POISED TO BOTTOM OUT IN THE LOWER-MID  
40S WELL INLAND, MID-UPPER 40S ACROSS THE COASTAL COUNTIES WITH  
MID-UPPER 50S AT THE BEACHES AND DOWNTOWN CHARLESTON.  
 
THROUGH TONIGHT: A WEST TO NORTHWEST FLOW ALOFT WILL PERSIST  
ACROSS THE SOUTHEAST U.S. THROUGH TONIGHT AS THE SPRAWLING  
VERTICALLY STACKED CYCLONE OVER SOUTHERN ONTARIO AND QUEBEC  
BEGINS TO SLOWLY WEAKEN AND PROPAGATES FARTHER INTO EASTERN  
CANADA. SURFACE HIGH PRESSURE CENTERED OVER THE DEEP SOUTH THIS  
MORNING WILL MEANDER INTO THE SOUTHEAST U.S. BY TONIGHT. THIS  
COUPLED WITH A MODEST DOWNSLOPE FLOW OFF THE SOUTHERN APPALACHIANS  
WILL KEEP QUIET CONDITIONS IN PLACE. HIGHS THIS AFTERNOON WILL  
WARM INTO THE MID-UPPER 70S ACROSS THE LOWCOUNTRY WITH UPPER  
70S/LOWER 80S ACROSS SOUTHEAST GEORGIA. THIS IS A DEGREE OR TWO  
WARMER THAN LOCAL LOW-LEVEL THICKNESS SCHEMES WOULD SUGGEST, BUT  
LOCAL UPWARD ADJUSTMENTS WERE MADE TO ACCOUNT FOR AT LEAST SOME  
WARMING INFLUENCES FROM 925-700 HPA DOWNSLOPE TRAJECTORIES.  
 
FOR TONIGHT, THE BOUNDARY LAYER SHOULD DECOUPLE BY EARLY-MID  
EVENING FOR MOST LOCATIONS. CLEAR SKIES, LOW DEWPOINTS, DRY SOIL  
CONDITIONS AND CALM/LIGHT WINDS ALL SUPPORT ANOTHER NIGHT OF  
STRONG RADIATIONAL COOLING. AS NOTED FOR THE PAST SEVERAL  
NIGHTS, THE NBM HAS BEEN EXHIBITING A GLARING WARM-BIAS IN  
STRONG RADIATIONAL COOLING REGIMES FOR MUCH OF THE FALL SEASON.  
THE 23/01Z NBM IS SHOWING A SIMILAR BEHAVIOR, ESPECIALLY OVER  
THE COASTAL COUNTIES, WHERE PREVIOUS NBM 01Z CYCLES HAVE BEEN AS  
MUCH AS 5-9 DEGREES TOO WARM IN AREAS. GIVEN THE ONGOING FIRE  
WEATHER SUPPORT TO STATE AND FEDERAL PARTNERS FOR WHICH  
TEMPERATURES ARE A CRITICAL COMPONENT, NATIONAL "BREAK THE  
GLASS" CRITERIA IS MET, THUS SIGNIFICANT LOCAL ADJUSTMENTS TO  
THE NBM WERE MADE ONCE AGAIN TO BETTER REFLECT A STRONG  
RADIATIONAL SETUP. LOWS WILL RANGE FROM THE MID-UPPER 40S INLAND  
AND ACROSS THE FRANCIS MARION NATIONAL FOREST TO THE UPPER  
40S/LOWER 50S ACROSS THE COASTAL COUNTIES WITH MID-UPPER 50S AT  
THE BEACHES AND DOWNTOWN CHARLESTON.  
 
 
   
SHORT TERM /FRIDAY THROUGH SUNDAY/  
 
DRY HIGH PRESSURE WILL REMAIN NORTH OF THE AREA FRIDAY THROUGH  
SUNDAY. AN UPPER SHORTWAVE WILL APPROACH ON SUNDAY, BRINGING AN  
INCREASE IN MID AND HIGH CLOUDS, BUT THE BEST RAIN CHANCES  
SHOULD HOLD OFF UNTIL SUNDAY NIGHT.  
 
 
   
LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/  
 
THE SURFACE HIGH OVER NEW ENGLAND WILL ERODE SUNDAY NIGHT AS A  
SERIES OF UPPER SHORTWAVES MOVES INTO THE EASTERN UNITED STATES.  
DECENT MOISTURE ADVECTION AND INCREASE IN UPPER FORCING WILL  
SUPPORT ISOLATED TO SCATTERED SHOWERS THROUGH EARLY TO MID NEXT  
WEEK. A STRONG COLD FRONT MAY SWEEP THROUGH LATE WEDNESDAY.  
 
 
   
AVIATION /04Z THURSDAY THROUGH MONDAY/  
 
23/06Z TAF DISCUSSION:  
KCHS/KJZI/KSAV: VFR THROUGH 25/06Z.  
 
EXTENDED AVIATION FORECAST: VFR.  
 
 
   
MARINE  
 
THROUGH TONIGHT: NORTHERLY WINDS WILL BECOME MORE VARIABLE THIS  
AFTERNOON AND ESPECIALLY TONIGHT AS HIGH PRESSURE BUILDS EAST  
INTO THE AREA. THE DAY WILL START OUT IN THE 10-15 KT RANGE WITH  
THE MARINE AREA SEEING THE TAIL END OF A NOCTURNAL SURGE WITH  
SPEEDS DROPPING TO <10 KT THIS AFTERNOON AND OVERNIGHT. SEAS  
WILL AVERAGE 1-3 FT THIS MORNING THEN 1-2 FT THIS AFTERNOON AND  
TONIGHT.  
 
FRIDAY THROUGH MONDAY: A PERSISTENT, TIGHT NE GRADIENT IS  
EXPECTED FRIDAY NIGHT THROUGH THE MIDDLE OF NEXT WEEK BEFORE A  
COLD FRONT SWEEPS THROUGH NEXT WEDNESDAY. SMALL CRAFT ADVISORY  
CONDITIONS WILL DEVELOP FOR ALL WATERS OUTSIDE CHARLESTON HARBOR  
FRIDAY NIGHT OR SATURDAY DUE TO A COMBINATION OF 25 KT WIND  
GUSTS AND SEAS BUILDING ABOVE 6 FT. CHARLESTON HARBOR WILL  
LIKELY NEED AN ADVISORY FOR SUNDAY INTO TUESDAY OR WEDNESDAY FOR  
20-25 KT WINDS.  
 
 
   
FIRE WEATHER  
 
A COMBINATION OF DEEP MIXING AND DRYING INFLUENCES FROM  
DOWNSLOPE TRAJECTORIES OFF THE SOUTHERN APPALACHIANS WILL  
SUPPORT ANOTHER DAY OF CRITICAL TO NEAR CRITICAL RH FOR THE  
LOWCOUNTRY AND SOUTHEAST GEORGIA. MIN RH VALUES ARE FORECAST TO  
DROP INTO THE 17-24% RANGE WEST OF I-95 AND 25-28% ELSEWHERE.  
FUELS ARE DRY, ESPECIALLY WEST OF I-95 WHERE D0-D2 DROUGHT IS  
IN PLACE AND OBSERVED FUEL MOISTURE WERE AT OR NEAR CRITICAL  
LEVELS WEDNESDAY AFTERNOON, BUT WINDS WILL BE VERY LIGHT. THE  
LIGHT WINDS WILL HELP TEMPER THE FIRE DANGER SOMEWHAT. PER  
COORDINATION WITH STATE AND FEDERAL PARTNERS, THERE IS NOT A  
NEED FOR A FIRE DANGER STATEMENT TODAY FOR THE LOWCOUNTRY OR  
SOUTHEAST GEORGIA.  
 
 
   
CHS WATCHES/WARNINGS/ADVISORIES  
 
GA...NONE.  
SC...NONE.  
MARINE...NONE.  
 
 
 
 
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