768  
FXUS62 KCHS 291802  
AFDCHS  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE CHARLESTON SC  
202 PM EDT TUE JUL 29 2025  
   
SYNOPSIS  
 
ATLANTIC HIGH PRESSURE WILL PREVAIL FOR MOST OF THE WEEK. A  
COLD FRONT WILL STALL NEAR THE AREA THIS WEEKEND.  
 
 
   
NEAR TERM /THROUGH TONIGHT/  
 
THE MID-LEVELS CONSIST OF A 598 DAM HIGH OVER THE SOUTHERN  
PLAINS AND THE LOWER MS VALLEY. IT STRETCHES INTO THE SOUTHEAST,  
WITH HEIGHTS FALLING TO ABOUT 594 DAM. THIS KEEPS US FIRMLY ON  
THE EASTERN PERIPHERY OF THE HIGH. AT THE SURFACE, TROUGHING IS  
OVER THE SOUTHEAST, WHILE HIGH PRESSURE IS IN THE ATLANTIC. THIS  
PATTERN IS USHERING DEEP MOISTURE INTO OUR AREA (PWATS AROUND  
2.25"). LIKEWISE, THE NBM HAS NUMEROUS SHOWERS AND THUNDERSTORMS  
DEVELOPING THIS AFTERNOON AND CONTINUE THROUGH THE EVENING.  
TEMPERATURES ARE WELL INTO THE 90S, SO A HEAT ADVISORY IS IN  
EFFECT FOR ALL OF OUR AREA. THIS DAYTIME HEATING IS GENERATING  
LOTS OF INSTABILITY. MLCAPES ARE UP TO 4,000-5,000 J/KG, WITH  
DCAPE VALUES RANGING FROM 700-1,000 J/KG. THIS ENVIRONMENT  
SUPPORTS THE POTENTIAL FOR A FEW STRONG TO MARGINALLY SEVERE  
STORMS CAPABLE OF PRODUCING DAMAGING WIND GUSTS. VERY SLOW STORM  
MOTION WILL ONCE AGAIN LEAD TO A RISK A LOCALLY HEAVY RAIN.  
FLOOD ADVISORIES ARE POSSIBLE. CONVECTION WILL GRADUALLY  
DISSIPATE LATE IN THE EVENING, LEADING TO MOSTLY DRY CONDITIONS  
BY MIDNIGHT. HOWEVER, WE CAN'T RULE OUT A FEW ISOLATED SHOWERS  
OVERNIGHT. LOWS WILL REMAIN MILD, RANGING FROM THE MID TO UPPER  
70S INLAND TO AROUND 80 DEGREES NEAR THE COAST.  
 
 
   
SHORT TERM /WEDNESDAY THROUGH FRIDAY/  
 
WEDNESDAY: SUBTROPICAL RIDGING WILL BRIEFLY REBUILD/CONSOLIDATE  
OFF THE SOUTHEAST U.S. COAST ON WEDNESDAY AS A WEAK SURFACE  
TROUGH LINGERS ACROSS THE CSRA AND THE SOUTH CAROLINA MIDLANDS.  
HEAT AND HUMIDITY WILL PERSIST WHICH WILL SUPPORT MODERATE  
INSTABILITY AS HIGHS WARM INTO THE MID-UPPER 90S AND DEWPOINTS  
HOLD IN THE 70S. MODIFIED SOUNDINGS DO SHOW SOME DEGREE OF  
SUBSIDENCE NEAR TO JUST UNDER 700 HPA WHICH WILL LIKELY PLAY  
INTO CONVECTION SOMEWHAT, BUT CONDITIONS STILL LOOK TO SUPPORT  
SCATTERED TO POSSIBLY NUMEROUS SHOWERS/TSTMS DEVELOPING MID-LATE  
AFTERNOON. ACTIVITY MAY CONCENTRATE ACROSS THE INTERIOR FIRST  
WHERE BOUNDARIES FROM CONVECTION SPARKING ALONG THE INLAND  
SURFACE TROUGH INTERSECT WITH THE INLAND MOVING SEA BREEZE WITH  
MESOSCALE BOUNDARY INTERACTIONS LIKELY DRIVING HOW CONVECTION  
EVOLVES INTO THE EVENING HOURS. 29/13Z NBM POPS OF 50-70% INLAND  
WITH 30-60% CLOSER TO THE COAST LOOK REASONABLE. WITH RESPECT  
TO THE HEAT, HEAT INDICES ARE ANTICIPATED TO REACH THE 105-108  
RANGE WELL INLAND BEFORE THE ONSET OF CONVECTION WHILE VALUES  
WILL PEAK 108-112 AT THE COAST. A HEAT ADVISORY IS IN PLACE  
11AM-8PM WEDNESDAY FOR AREAS ROUGHLY ALONG/SOUTH OF A METTER-  
CLYO-JACKSONBORO-NORTH CHARLESTON- MCCLELLANVILLE LINE,  
INCLUDING ALL OF THE SAVANNAH METRO AREA AND PARTS OF THE  
CHARLESTON METRO AREA. CONVECTION WILL SLOWLY WIND DOWN THROUGH  
THE EVENING HOURS. OVERNIGHT LOWS WILL DROP INTO THE MID 70S  
WELL INLAND TO THE LOWER 80S AT THE COAST AND BEACHES.  
 
THURSDAY AND FRIDAY: THE SUBTROPICAL RIDGE ALOFT WILL SLOWLY  
WEAKEN WITH TIME AS SERIES OF SHORTWAVES PASSING BY WELL TO THE  
NORTH BEGIN TO CARVE OUT A LONGER WAVE TROUGH ACROSS THE EASTERN  
CONUS. THIS WILL SUPPORT A CONTINUED RISK FOR SCATTERED TO  
NUMEROUS SHOWER/TSTMS EACH AFTERNOON/EVENING. HIGHS WILL WARM  
INTO THE MID-UPPER 90S BOTH AFTERNOONS WITH LOWS FRIDAY MORNING  
DROPPING INTO THE MID 70S INLAND TO THE LOWER 80S AT THE COAST  
AND BEACHES. HEAT INDICES SHOULD PEAK 105-108 INLAND WITH  
108-112 ALONG/EAST OF I-95 BOTH AFTERNOONS PRIOR TO THE ONSET OF  
CONVECTION. ADDITIONAL HEAT ADVISORIES MAY BE NEEDED, BUT THESE  
WILL LARGELY BE DRIVEN BY THE TIMING AND EXTENT OF AFTERNOON  
CONVECTION.  
 
 
   
LONG TERM /FRIDAY NIGHT THROUGH MONDAY/  
 
THE PATTERN WILL BECOME QUITE A BIT MORE ACTIVE OVER THE  
WEEKEND AS A COLD FRONT STALLS OVER THE AREA AS THE LONGWAVE  
TROUGH SHARPENS ACROSS THE EASTERN UNITED STATES. THERE REMAINS  
SOME UNCERTAINTY ON QPF FOR THE WEEKEND (NOT UNEXPECTED GIVEN  
SYNOPTIC MODELS ARE TRYING TO RESOLVE CONVECTIVE ELEMENTS SO FAR  
OUT), BUT CONDITIONS LOOK TO BECOME MUCH MORE UNSETTLED ACROSS  
THE REGION AS THE FRONT STALLS OUT AND INTERACTS WITH A VERY  
MOIST (PWATS >2.25") AND UNSTABLE ENVIRONMENT. THE POTENTIAL IS  
CERTAINLY THERE FOR SEVERAL INCHES OF RAIN TO FALL SATURDAY INTO  
MONDAY WITH LOCALIZED STORM TOTAL AMOUNTS FOR THE 3-DAY PERIOD  
POTENTIALLY EXCEEDING 5 INCHES. THERE WILL BE A RISK FOR FLASH  
FLOODING, MAINLY IN THE BASE FLASH FLOOD CATEGORY (NOTE THE  
CHANGE IN FLASH FLOOD CRITERIA AT WFO CHARLESTON ON 1 AUGUST),  
BUT IS IT UNCLEAR AT THIS TIME IF THE RISK FOR FLASH FLOODING  
WILL BE WIDESPREAD ENOUGH FOR A FLOOD WATCH. THESE ARE DETAILS  
THAT WILL NEED TO BE WORKED OUT OVER THE COMING DAYS. WITH THE  
RAIN AND INCREASED CLOUD COVER COMES CONSIDERABLY "COOLER"  
CONDITIONS. TEMPERATURES WILL FALL TO WELL BELOW NORMAL LEVELS  
FOR THIS TIME OF YEAR, WHICH WILL FEEL MUCH MORE REFRESHING  
AFTER THE MANY DAYS OF EXCESSIVE HEAT THAT THE AREA HAS  
EXPERIENCED.  
 
 
   
AVIATION /18Z TUESDAY THROUGH SUNDAY/  
 
18Z TAFS: CONVECTION IS FORMING ALONG THE SEA BREEZE AND WILL  
VERY SLOWLY MOVE INLAND THIS AFTERNOON. SINCE THE CONVECTION IS  
EITHER OVER OF IN VERY CLOSE PROXIMITY TO THE TAF SITES, BRIEF  
IFR IS POSSIBLE DUE REDUCED VISIBILITIES IN HEAVY RAIN. WE  
ACCOUNTED FOR THIS IN THE TEMPO GROUPS. AMENDMENTS MAY BE  
NEEDED IN THE END TIMING. CONVECTION IS EXPECTED TO GRADUALLY  
DIMINISH DURING THE LATE EVENING, WITH A RETURN TO VFR  
OVERNIGHT. THERE ARE HINTS AT ISOLATED CONVECTION OVERNIGHT, BUT  
NOT TO THE POINT THAT WE HAVE IT MENTIONED IN THE TAFS. ONLY  
TOWARDS THE END OF THE TAF TIME PERIOD, DO WE HAVE VCSH, HINTING  
AT THE POTENTIAL FOR ANOTHER ROUND OF CONVECTION.  
 
EXTENDED AVIATION FORECAST: THE RISK FOR FLIGHT RESTRICTIONS  
DUE TO SHOWERS/TSTMS WILL PERSIST EACH AFTERNOON/EVENING WITH  
CHANCES RAMPING UP OVER THE WEEKEND.  
 
 
   
MARINE  
 
REST OF TODAY AND TONIGHT: S TO SE WINDS WILL VEER TO THE S  
THIS EVENING AS THE SEA BREEZE WEAKENS. OVERNIGHT WINDS WILL  
GENERALLY BE S 5-10 KT. SEAS SHOULD BE 1-2 FT WITHIN 20 NM AND  
2-3 FT FOR THE GA WATERS BEYOND 20 NM.  
 
WEDNESDAY THROUGH SUNDAY: SOUTHERLY WIND REGIME WILL PREVAIL  
THROUGH FRIDAY. WINDS WILL BEGIN TO TURN NORTHEAST OVER THE  
WEEKEND AS A COLD FRONT STALLS OUT NEAR THE AREA. WINDS WILL  
GENERALLY REMAIN 15 KT OR LESS THROUGH THE PERIOD, ALTHOUGH  
WINDS MAY GET AS HIGH AS 15- 20 KT OVER THE WEEKEND ACROSS  
MAINLY THE SOUTH CAROLINA WATERS AS THE GRADIENT PINCHES A BIT  
BEHIND THE COLD FRONT.  
 
 
   
CLIMATE  
 
RECORD HIGH MINIMUM TEMPERATURES:  
 
JULY 29:  
KCHS: 80/2016  
 
JULY 30:  
KCHS: 81/2016  
KCXM: 83/2016  
 
JULY 31:  
KCHS: 80/2022  
KSAV: 80/2010  
 
AUGUST 1:  
KCHS: 81/1999  
KSAV: 79/2020  
 
 
   
CHS WATCHES/WARNINGS/ADVISORIES  
 
GA...HEAT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR GAZ087-088-  
099>101-114>119-137>141.  
HEAT ADVISORY FROM 11 AM TO 8 PM EDT WEDNESDAY FOR GAZ099>101-  
114>119-137>141.  
SC...HEAT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR SCZ040-042>045-  
047>052.  
HEAT ADVISORY FROM 11 AM TO 8 PM EDT WEDNESDAY FOR SCZ047>052.  
MARINE...NONE.  
 
 
 
 
 
NEAR TERM...  
SHORT TERM...  
LONG TERM...  
AVIATION...  
MARINE...  
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