549  
FXUS62 KCHS 210000  
AFDCHS  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE CHARLESTON SC  
800 PM EDT TUE MAY 20 2025  
   
SYNOPSIS
 
 
A COLD FRONT WILL PUSH OFFSHORE WEDNESDAY AFTERNOON INTO  
WEDNESDAY EVENING, FOLLOWED BY HIGH PRESSURE THROUGH THE  
WEEKEND.  
 

 
   
NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/
 
 
QUIET CONDITIONS AS THE BOUNDARY LAYER STABILIZES AND WE RETURN  
TO A SOUTHWESTERLY FLOW AT THE SURFACE. WINDS WILL BE PICKING  
UP AS THE SURFACE PRESSURE GRADIENT INCREASES AHEAD OF AN  
APPROACHING COLD FRONT. LOW TEMPERATURES WILL BE IN THE 70S.  
 

 
   
SHORT TERM /6 AM WEDNESDAY MORNING THROUGH FRIDAY/
 
 
WEDNESDAY: A BROKEN LINE OF SHOWERS/TSTMS AHEAD OF AN APPROACHING  
COLD FRONT WILL BE IN A WEAKENING PHASE AS IT APPROACHES THE FAR  
INTERIOR AREAS PRIOR TO DAYBREAK. SOME REMNANT SHOWER/TSTM ACTIVITY  
COULD PUSH INTO INTERIOR SOUTHEAST GEORGIA JUST AFTER DAYBREAK, BUT  
CONFIDENCE IN ANYTHING MEANINGFUL HAPPENING IS LOW. GUIDANCE STILL  
SHOWS LITTLE IN THE WAY OF SIGNIFICANT FORCING AHEAD OF THE FRONT  
WITH MODEL CROSS SECTIONS SHOWING THE CORRIDOR OF STRONGEST UVVS  
DISPLACED TO THE NORTH WHERE A PASSING SHORTWAVE/VORTICITY LOBE WILL  
TRAVERSE NORTH CAROLINA. SOME LOW-LEVEL FORCING IS NOTED, LIKELY  
ALONG/NEAR THE FRONTAL SURFACE ITSELF, BUT THE BEST 850 HPA THETA-E  
POOLING WILL OCCUR SOUTH OF I-16 DURING PEAK HEATING AND THIS IS  
WHERE THE BEST OVERLAP OF INSTABILITY AND THETA-E WILL OCCUR. GIVEN  
THE WESTERLY LOW-LEVEL FLOW AHEAD OF THE FRONT WITHIN AN ENVIRONMENT  
WITHOUT ANY STRONG FORCING MECHANISMS, IT IS UNCLEAR EXACTLY HOW  
MUCH COVERAGE OF SHOWERS/TSTMS WILL OCCUR DURING THE AFTERNOON HOURS  
AND ITS VERY POSSIBLE CONVECTION WILL REMAIN LARGELY ABSENT THROUGH  
FROPA. A BLEND OF THE LATEST HREF AND 13Z NBM WAS FAVORED TO  
CONSTRUCT POPS, WHICH YIELDS RAIN CHANCES OF 10-30%, HIGHEST ACROSS  
THE GEORGIA COASTAL COUNTIES. THE FRONT SHOULD CLEAR THE COAST  
DURING THE EVENING HOURS WHICH WILL END ANY CHANCE FOR MEASURABLE  
RAIN. MODIFIED SOUNDINGS DO SHOW MODEST TO LOCALLY STRONG MIXED-  
BASED INSTABILITY WITHIN A BELT OF AROUND 30 KT OF 0-6KM BULK SHEAR.  
THIS COULD SUPPORT AN ISOLATED SEVERE TSTM WITH DAMAGING WINDS AND  
LARGE HAIL, BUT AN ORGANIZED SEVERE WEATHER EVENT SEEMS HIGHLY  
UNLIKELY AT THIS TIME. HIGHS WILL WARM INTO THE LOWER-MID 90S, A BIT  
COOLER AT THE BEACHES WHERE A PINNED SEA BREEZE WILL BE LATE TO FORM.  
 
THURSDAY AND FRIDAY: A MODEST CYCLONIC FLOW ALOFT WILL PREVAIL  
THROUGH THE PERIOD AS HIGH PRESSURE TRIES TO BE BUILD INTO THE  
REGION. A WEAK, SECONDARY COLD FRONT WILL PUSH OFFSHORE THURSDAY  
EVENING WHICH WILL HELP TO REINFORCE THE RELATIVELY COOLER AND DRIER  
AIRMASS THAT WILL FILTER IN ON THURSDAY. THE FRONT WILL PASS THROUGH  
DRY WITH NO MEANINGFUL MOISTURE RETURN OCCURRING PRIOR TO IS  
PASSAGE. HIGHS WILL WARM INTO THE UPPER 80S/LOWER 90S THURSDAY WITH  
80S FOR FRIDAY (MAYBE EVEN A FEW UPPER 70S ACROSS THE FAR INTERIOR  
ADJACENT TO THE CSRA). LOWS FRIDAY MORNING WILL DROP INTO THE LOWER  
60S WELL INLAND TO AROUND 70 AT THE BEACHES AND DOWNTOWN  
CHARLESTON.  
 

 
   
LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/
 
 
MOSTLY QUIET CONDITIONS WILL PREVAIL FOR MUCH OF THE EXTENDED  
PERIOD. RAIN CHANCES WILL INCREASE SLIGHTLY SUNDAY INTO MONDAY AS A  
WEAK WARM FRONT LIFTS NORTH THROUGH THE AREA AHEAD OF A DEVELOPING  
STORM SYSTEM TO THE WEST. TEMPERATURES WILL START OUT NEAR TO  
SLIGHTLY BELOW NORMAL OVER THE UPCOMING WEEKEND, THEN BEGIN TO  
RECOVER BACK TO LEVELS SLIGHTLY ABOVE NORMAL.  
 

 
   
AVIATION /00Z WEDNESDAY THROUGH SUNDAY/
 
 
00Z TAFS: MAINLY VFR. A COLD FRONT MAY BRING SOME SHOWERS AND  
THUNDERSTORM ON THURSDAY. BUT PROBABILITIES WILL BE TOO LOW TO  
WARRANT MENTION IN THE TAFS. ADDITIONALLY, GUSTY WINDS ARE  
EXPECTED LATE IN THE TAF TIME PERIOD.  
 
EXTENDED AVIATION OUTLOOK: THERE ARE NO CONCERNS WITH A >50%  
CONFIDENCE LEVEL.  
 

 
   
MARINE
 
 
TONIGHT: S WINDS WILL VEER TO THE SW OVERNIGHT. SEAS WILL  
AVERAGE 2-3 FT.  
 
WEDNESDAY: SOUTHWEST WINDS WILL INCREASE AHEAD OF AN APPROACHING  
COLD FRONT. WINDS COULD GET AS HIGH AS 15-20 KT OVER THE SOUTH  
SANTEE-EDISTO BEACH NEARSHORE LEG AND CHARLESTON HARBOR DURING THE  
AFTERNOON HOURS. GUSTS COULD GET CLOSE TO 25 KT, BUT ITS DURATION IS  
SOMEWHAT UNCERTAIN. FOR THIS REASON, A SMALL CRAFT ADVISORY HAS NOT  
BEEN ISSUED. THE NEED FOR AN ADVISORY WILL BE REEVALUATED OVERNIGHT.  
WINDS WILL SHIFT OFFSHORE DURING THE EVENING HOURS AS A COLD FRONT  
SHIFTS OFFSHORE. SEAS WILL BUILD 2-3 FT, EXCEPT 4-5 FT OVER THE  
SOUTH SANTEE-EDISTO BEACH NEARSHORE LEG.  
 
THURSDAY THROUGH SUNDAY: THERE ARE NO MAJOR CONCERNS. OFFSHORE WINDS  
WILL TURN BACK MORE SOUTHWESTERLY THURSDAY BEFORE RETURNING OFFSHORE  
THURSDAY NIGHT AS A REINFORCING COLD FRONT SHIFTS OFFSHORE. OFFSHORE  
WINDS WILL PERSIST THROUGH FRIDAY BEFORE TURNING NORTHERLY SATURDAY  
AHEAD OF A DEVELOPING WARM FRONT. WINDS WILL THEN VEER SOUTHERLY  
SUNDAY AS THE WARM FRONT LIFTS NORTH.  
 

 
   
CLIMATE
 
 
RECORD HIGH MINIMUM TEMPERATURES:  
MAY 20:  
KCHS: 72/2022  
KCXM: 76/2022  
KSAV: 73/1896  
 
MAY 21:  
KCHS: 74/2022  
KCXM: 78/1998  
KSAV: 74/2017  
 

 
   
CHS WATCHES/WARNINGS/ADVISORIES
 
 
GA...NONE.  
SC...NONE.  
MARINE...NONE.  
 

 
 

 
 
NEAR TERM...  
SHORT TERM...  
LONG TERM...  
AVIATION...  
MARINE...  
 
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