822  
FXUS62 KCHS 300744  
AFDCHS  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE CHARLESTON SC  
344 AM EDT TUE MAY 30 2017  
   
SYNOPSIS
 
 
WEAK HIGH PRESSURE WILL PERSIST OVER THE WESTERN ATLANTIC WHILE  
A SURFACE TROUGH RESIDES INLAND THROUGH THE WEEKEND. A COLD  
FRONT MAY IMPACT THE AREA EARLY NEXT WEEK.  
 

 
   
NEAR TERM /THROUGH TONIGHT/
 
 
TODAY: THE PATTERN ALOFT WILL SOLIDLY FEATURE SOUTHWESTERLY  
FLOW AS THE REGION SITS BETWEEN THE ANTICYCLONE OVER THE  
ATLANTIC AND A LARGE UPPER LOW SITUATED NORTH OF THE GREAT  
LAKES. AT THE SURFACE, THE PATTERN IS RATHER DIFFUSE AND  
NEBULOUS WITH WEAK HIGH PRESSURE TO THE SOUTHWEST AND  
SUBTROPICAL HIGH PRESSURE OVER THE ATLANTIC. WESTERLY FLOW WILL  
PREVAIL IN THE LOW LEVELS FOR MUCH OF THE DAY, WITH A TURN TO  
THE SOUTHWEST IN THE LATE AFTERNOON WITH THE INLAND ADVANCEMENT  
OF THE SEA BREEZE ALONG THE COAST. IT IS QUITE STRIKING TO SEE  
THE MODEL AGREEMENT FOR TODAY. VIRTUALLY EVERY MODEL AVAILABLE  
FAVORS THE GEORGIA COAST FOR CONVECTIVE DEVELOPMENT IN THE MID  
TO LATE AFTERNOON HOURS. IT'S HARD TO IGNORE THIS CONSENSUS, AND  
IT IS FURTHER SUPPORTED BY MODEL SOUNDINGS WHICH SHOW A SOLID  
CAP HOLDING OUTSIDE OF LOCATIONS IN AND AROUND THE SOUTHEAST  
GEORGIA COAST. AS SUCH, 30-40 PERCENT CHANCES ARE IN PLACE IN  
THIS AREA, MAINLY FROM AROUND 4 PM AND LATER. A SLIGHT CHANCE IS  
IN PLACE ELSEWHERE AS THE CAP MAY BE ABLE TO BREAK VERY LATE,  
BUT COVERAGE SHOULD BE LIMITED TO ISOLATED. ALONG THE GEORGIA  
COAST THERE WILL EVEN BE A MODEST RISK OF A COUPLE STRONG TO  
SEVERE STORMS. SOUNDINGS FROM SAV TO SSI FEATURE CAPE VALUES  
AROUND 2000 J/KG WITH DCAPE AROUND 1000 J/KG. MID-LEVEL LAPSE  
RATES ARE 6-6.5 C AT WORST, BUT GIVEN THAT THE ENVIRONMENT IS  
UNTAPPED FOR THE LAST FEW DAYS, IT IS CERTAINLY PLAUSIBLE WITH  
BOUNDARY INTERACTIONS THAT A COUPLE STRONG/SEVERE STORMS WILL BE  
POSSIBLE. WILL FOCUS THE MENTION IN THE HAZARDOUS WEATHER  
OUTLOOK TO THIS AREA. TEMPERATURES WILL BE COOLER THAN DAYS PAST  
THANKS TO MORE LINGERING CLOUDINESS. THE FORECAST ADVERTISES  
HIGHS AROUND 90 JUST ABOUT EVERYWHERE.  
 
TONIGHT: WE WILL HAVE TO WAIT AND SEE HOW THE DAYTIME  
CONVECTION EVOLVES, BUT IT LOOKS LIKE MOST OF THE OVERNIGHT  
ACTIVITY WILL BE OFFSHORE. HOWEVER, ISOLATED SHOWERS AND STORMS  
WILL BE POSSIBLE ALONG THE COAST THROUGH THE NIGHT DEPENDING ON  
RESIDUAL BOUNDARIES AND THE PERSISTENT WARM/MOIST AIRMASS. LOWS  
WILL ONLY FALL INTO THE LOW 70S FOR MOST AREAS.  
 

 
   
SHORT TERM /WEDNESDAY THROUGH FRIDAY/
 
 
SOMEWHAT DRIER AIR WILL PUSH INTO THE AREA WEDNESDAY INTO  
THURSDAY AS A WEAK FRONT STALLS ALONG THE GA COAST. WEAK  
SHORTWAVE ENERGY MAY AFFECT THE AREA LATER ON WEDNESDAY THOUGH  
THE DECREASING SURFACE DEWPOINTS WILL LIMIT SURFACE-BASED  
INSTABILITY. A MODERATE CAP WILL TEND TO LIMIT CONVECTIVE  
DEVELOPMENT BUT WE MAINTAINED ISOLATED POPS DURING THE  
AFTERNOON.  
 
DRIER LOW-LEVELS AND THE ONSET OF SOME NVA MAY REDUCE  
CONVECTIVE COVERAGE ON THURSDAY, THOUGH WE HELD ONTO A LOW-END  
SLIGHT CHANCE POPS.  
 
THE STALLED FRONT POTENTIALLY STARTS LIFTING NORTH ON FRIDAY,  
BRINGING SURFACE DEWPOINTS BACK CLOSE TO 70 BY AFTERNOON. NVA  
COULD AFFECT SC DURING THE AFTERNOON BUT FARTHER INLAND ACROSS  
SOUTHEAST GA WE SHOW SCATTERED SHOWERS AND TSTMS MAINLY IN THE  
AFTERNOON.  
 

 
   
LONG TERM /FRIDAY NIGHT THROUGH MONDAY/
 
 
A MORE PRONOUNCED UPPER TROUGH PATTERN OVER THE WEEKEND WILL  
BRING INCREASED MOISTURE AND BETTER FORCING FOR CONVECTION. IT'S  
POSSIBLE A COLD FRONT WILL MOVE INTO THE AREA MONDAY OR  
TUESDAY. WE CONTINUE TO SHOW HIGHER POPS DURING THE LONG TERM  
PERIOD.  
 

 
   
AVIATION /08Z TUESDAY THROUGH SATURDAY/
 
 
VFR CONDITIONS ARE LIKELY TO PERSIST AT BOTH KCHS AND KSAV  
THROUGH 06Z WEDNESDAY. THE MAIN THING OF NOTE IS THAT THERE IS  
EXCELLENT MODEL AGREEMENT THAT THUNDERSTORM DEVELOPMENT IS  
FAVORED ALONG THE GEORGIA COAST LATE THIS AFTERNOON. THIS MEANS  
THAT CONVECTIVE ACTIVITY WILL LIKELY BE ONGOING AT LEAST IN THE  
VICINITY OF KSAV BY THE MID/LATE AFTERNOON. HAVE ADDED VCTS TO  
THE FORECAST STARTING AT 22Z AND LET IT PREVAIL THROUGH 00Z.  
 
EXTENDED AVIATION OUTLOOK: MAINLY VFR. BRIEF FLIGHT  
RESTRICTIONS POSSIBLE IN ISOLATED AFTERNOON/EVENING SHOWERS AND  
TSTMS.  
 

 
   
MARINE
 
 
TODAY THROUGH TONIGHT: WESTERLY FLOW WILL PREVAIL FOR MUCH OF  
THE DAY BEFORE TURNING SOUTHWESTERLY LATE AS THE DIURNAL SEA  
BREEZE SETS UP. THEN OVERNIGHT, SOUTHWEST FLOW WILL GENERALLY  
PREVAIL. WINDS WILL GENERALLY TOP OUT IN THE 10-15 KNOT RANGE.  
EVEN IN THE CHARLESTON HARBOR WINDS WILL LIKELY FALL SHORT OF  
THE 15-20 KNOT RANGE THAT HAS BEEN SO PREVALENT THE LAST FEW  
DAYS. SEAS WILL BE AROUND 2 FEET.  
 
FAIRLY WEAK WINDS AND SMALL SEAS ARE EXPECTED TO PERSIST OVER  
THE ATLANTIC WATERS AND CHARLESTON HARBOR WEDNESDAY THROUGH  
FRIDAY AS WEAK HIGH PRESSURE PERSISTS OVER THE WESTERN ATLANTIC.  
AS THE HIGH STRENGTHENS OVER THE WEEKEND, SLIGHTLY STRONGER  
WIND FIELDS WILL RESULT. THE SEA BREEZE LOOKS QUITE WEAK THROUGH  
FRIDAY, THEN SLIGHTLY STRONGER DURING THE AFTERNOONS ON  
SATURDAY AND SUNDAY.  
 

 
   
EQUIPMENT
 
 
AFTERNOON TEMPERATURE READINGS FROM KSAV STILL APPEAR TO BE  
ERRONEOUSLY RUNNING A COUPLE OF DEGREES WARMER THAN SURROUNDING  
SITES. AS SUCH, HIGH TEMPERATURE OBSERVATIONS FROM THE SITE ARE  
CONSIDERED UNRELIABLE. TECHNICIANS WILL INVESTIGATE THE ISSUE  
TODAY.  
 

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

 
 

 
 
NEAR TERM...BSH  
SHORT TERM...JRL  
LONG TERM...JRL  
AVIATION...BSH/JRL  
MARINE...BSH/JRL  
EQUIPMENT...BSH  
 
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