622  
FXUS62 KCHS 251128  
AFDCHS  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE CHARLESTON SC  
728 AM EDT TUE JUL 25 2017  
   
SYNOPSIS
 
 
BROAD LOW PRESSURE WILL REMAIN ACROSS THE CAROLINAS AND GEORGIA  
TODAY. A WEAK COLD FRONT WILL THEN STALL NORTH OF THE AREA  
WEDNESDAY BEFORE WEAK LOW PRESSURE LINGERS OVER THE AREA  
THROUGH LATE WEEK. ANOTHER COLD FRONT WILL APPROACH THE REGION  
THIS WEEKEND BEFORE STALLING OVER OR NEAR THE AREA EARLY NEXT  
WEEK.  
 

 
   
NEAR TERM /THROUGH TONIGHT/
 
 
TODAY: DEEP MOISTURE, A WEAK MID LEVEL DISTURBANCE DRIFTING EAST  
THROUGH GEORGIA, AND INCREASING UPPER DIFLUENCE WILL SPELL AN ACTIVE  
CONVECTIVE DAY ACROSS THE FORECAST AREA. THIS WILL BE ESPECIALLY  
TRUE ALONG THE SAVANNAH RIVER AND ACROSS SOUTHEAST GA, WHERE THE  
EAST-WEST AXIS OF HIGHER PWATS IS FORECAST TO PERSIST. COVERAGE IS  
EXPECTED TO INCREASE TO SCATTERED TO NUMEROUS ALONG AND SOUTH OF  
I-16 DURING MID TO LATE AFTERNOON AS SHOWERS AND STORMS PROLIFERATE  
FREELY IN THE PLUME OF DEEP MOISTURE ON MESOSCALE BOUNDARIES COLLISIONS.  
OUR HIGHEST POPS IN THE 70 PERCENT RANGE FOR THE AFTERNOON, EXTEND  
FROM MUCH OF SOUTHEAST GA INTO JASPER AND BEAUFORT COUNTIES WILL  
A RIBBON OF LIKELY POPS EXTENDED NORTHEAST ALONG THE SC SEA BREEZE  
COVERAGE.  
 
THE MAIN RISK FOR HAZARDOUS WEATHER TODAY APPEARS TO BE A LOWER-  
END THREAT FOR LOCALIZED FLOODING AND VERY HEAVY RAINFALL POTENTIAL  
IN THE STRONGEST CONVECTION. STORM MOTIONS LOOK WEAK LATER TODAY  
AND MULTI-CELL CONVECTION SHOULD BE DRIVEN ON BOUNDARY INTERACTIONS.  
THE NSSL WRF FAVORS THE I-95 CORRIDOR EITHER SIDE OF SAVANNAH TODAY  
AND THIS SEEMS TO CORRELATE WITH THE GLOBAL MODEL QPF OUTPUT AS  
WELL. HIGH TEMPS WILL BE IN THE UPPER 80S TO NEAR 90, CONVECTIVE  
TEMPS ARE MAINLY IN THE UPPER 80S. CONVECTIVE PROCESSES WILL RESULT  
IN MOSTLY CLOUDY TO CLOUDY SKIES MANY AREAS BY LATER THIS AFTERNOON.  
 
TONIGHT: THE FORECAST REMAINS ON THE TRICKY SIDE. A WEAK MID  
LEVEL LOW WILL MOVING INTO THE WESTERN HALF OF THE FORECAST  
AREA OVERNIGHT AND MOISTURE WILL REMAIN VERY DEEP. SURFACE WINDS  
COULD SHIFT ONSHORE ALONG THE UPPER SC COAST LATE, RESULTING IN  
BETTER MOISTURE CONVERGENCE AND COASTAL SHOWERS AND STORMS LATE.  
INLAND AREAS MAY ALSO SEE ISOLATED TO SCATTERED CONVECTIVE RAINS  
LINGERING THROUGH THE NIGHT AND WE MAINTAINED CHANCE POPS TO  
COVER. TEMPS WILL PROBABLY REMAIN IN THE MID/UPPER 70S THROUGH  
THE NIGHT.  
 

 
   
SHORT TERM /WEDNESDAY THROUGH FRIDAY/
 
 
WEDNESDAY: A WEAK COLD FRONT WILL LIKELY STALL NORTH OF THE REGION  
EARLY WHILE A MID/UPPER LVL TROUGH OF LOW PRESSURE SHIFTS FURTHER  
OFF THE NORTHEAST COAST. HOWEVER, BROAD LOW PRESSURE WILL LIKELY  
PERSIST ALONG AND SOUTH OF THE FRONT WITHIN MODERATELY UNSTABLE AND  
MOIST CONDITIONS. WEAK FORCING ASSOCIATED WITH THE BROAD AREA OF LOW  
PRESSURE AND DEEP MOISTURE CHARACTERIZED BY PWATS NEAR 2.25 INCHES  
SUPPORT NUMEROUS SHOWERS AND THUNDERSTORMS DURING LATE MORNING INTO  
EVENING HOURS OVER MUCH OF THE AREA. PRECIP ACTIVITY AND MOSTLY  
CLOUDY SKIES WILL LIKELY LIMIT HIGH TEMPS TO THE MID/UPPER 80S. A  
FEW SHOWERS AND/OR THUNDERSTORMS COULD LINGER INTO THE OVERNIGHT  
PERIOD. OVERNIGHT LOWS WILL RANGE IN THE LOW/MID 70S.  
 
THURSDAY: WHAT'S LEFT OF A SFC TROUGH/BROAD AREA OF LOW PRESSURE  
WILL SLOWLY DRIFT OFFSHORE DURING THE DAY. HOWEVER, LINGERING  
MOISTURE AND THE POSITION OF THE MID-LVL LOW SHOULD SUPPORT CHANCES  
OF SHOWERS AND THUNDERSTORMS OVER MUCH OF THE AREA. THE BULK OF  
PRECIP ACTIVITY SHOULD TREND TOWARD THE COAST OF SOUTHEAST GEORGIA  
LATER IN THE DAY. NEAR THE GEORGIA COAST, NUMEROUS SHOWERS AND  
THUNDERSTORMS WILL BE POSSIBLE THROUGH THE AFTERNOON WHILE THE MID-  
LVL LOW SLOWLY MEANDERS OFF THE SOUTHEAST COAST. CLOUD COVER WILL  
LIMIT MAX TEMPS TO AROUND 90 DEGREES. SHOWER AND THUNDERSTORMS ARE  
EXPECTED TO TAPER OFF DURING THE OVERNIGHT PERIOD. LOW TEMPS SHOULD  
RANGE IN THE MID 70S.  
 
FRIDAY: CONDITIONS SHOULD BE SLIGHTLY DRIER TO START OFF THE WEEKEND  
WHILE THE AREA SEES A TRANSITION FROM LOW PRESSURE SHIFTING FURTHER  
OFFSHORE AND STRONGER LOW PRESSURE DEVELOPING INLAND. HOWEVER, A  
SOUTHWEST FLOW SHOULD BEGIN TO ADVECT GREATER LEVELS OF MOISTURE TO  
THE AREA, WARRANTING CHANCES OF AFTERNOON SHOWERS AND THUNDERSTORMS  
WELL AHEAD OF A COLD FRONT APPROACHING THE REGION LATE. TEMPS WILL  
LIKELY BE WARMER, PEAKING IN THE LOWER 90S.  
 

 
   
LONG TERM /FRIDAY NIGHT THROUGH MONDAY/
 
 
DEEP MOISTURE WILL ADVECT TO THE SOUTHEAST UNITED STATES AHEAD OF A  
COLD FRONT THAT IS EXPECTED TO MOVE INTO THE AREA SATURDAY. PWATS  
BETWEEN 2.25 TO 2.5 INCHES AND FORCING ASSOCIATED WITH THE FRONT  
SUPPORT NUMEROUS SHOWERS AND THUNDERSTORMS SATURDAY INTO SUNDAY  
WHILE THE FRONT SLOWLY PROGRESSES SOUTH AND EVENTUALLY STALLS OVER  
OR NEAR SOUTHERN AREAS OF SOUTHEAST GEORGIA. A FEW THUNDERSTORMS  
COULD BECOME MORE ORGANIZED THAN PREVIOUS DAYS GIVEN GREATER WIND  
FIELDS ALOFT, BUT THE OVERALL THREAT OF STRONGER THUNDERSTORMS COULD  
BE LIMITED DUE TO THE TIMING OF FROPA DURING EARLIER HOURS ON  
SATURDAY. AT LEAST CHANCES OF SHOWERS AND THUNDERSTORMS COULD LINGER  
INTO EARLY NEXT WEEK WHILE MOISTURE CONTINUES TO LIFT OVER OR NEAR  
THE STATIONARY FRONT.  
 
TEMPS WILL GENERALLY BE A FEW DEGREES BELOW NORMAL THIS WEEKEND AND  
EARLY NEXT WEEK GIVEN EXTENSIVE CLOUD COVER AND PRECIP ACTIVITY. IN  
GENERAL, TEMPS SHOULD PEAK IN THE MID/UPPER 80S. OVERNIGHT LOWS WILL  
RANGE IN THE LOW/MID 70S.  
 

 
   
AVIATION /11Z TUESDAY THROUGH SATURDAY/
 
 
KCHS: VFR CONDITIONS LIKELY THIS MORNING, ALTHOUGH SOME IFR CIGS  
LURKED NOT FAR TO THE WEST AT SUNRISE. 06Z NAM SOUNDING SHOWS  
SOME CHANCES OF LOW CIGS THROUGH 15Z, BUT WE ARE OPTING VFR AT  
THIS TIME. WE MAINTAINED VCTS THIS AFTERNOON AND ALSO INTRODUCED  
SOME SHOWER CHANCES LATER TONIGHT WITH AN UPPER LEVEL DISTURBANCE  
IN THE REGION AND DEEP LEVEL MOISTURE AT HIGH LEVELS.  
 
KSAV: DEEP MOISTURE SHOULD RESULT IN A GOOD POTENTIAL FOR THUNDER  
AND SOME HEAVY DOWNPOURS IN THE GENERAL AREA THIS AFTERNOON. PRIOR  
TO THEN, A POTENTIAL FOR SOME LOW CLOUDS AND SLIGHT CHANCES FOR  
BRIEF IFR/MVFR THROUGH MID MORNING. MAINLY VFR TONIGHT BUT CANNOT  
RULE OUT SOME LOW CLOUDS OR EVEN A SHOWER LATE.  
 
EXTENDED AVIATION OUTLOOK: BRIEF FLIGHT RESTRICTIONS ARE POSSIBLE  
WITH SHOWERS AND THUNDERSTORMS, ESPECIALLY WEDNESDAY INTO EARLY  
THURSDAY AS WEAK LOW PRESSURE APPROACHES THE REGION. VFR CONDITIONS  
SHOULD PREVAIL LATE THURSDAY AND FRIDAY, BEFORE FLIGHT RESTRICTIONS  
RETURN WITH SHOWERS AND THUNDERSTORMS ALONG/NEAR ANOTHER COLD FRONT  
SATURDAY.  
 

 
   
MARINE
 
 
SOUTHWEST SYNOPTIC FLOW WILL PERSIST TODAY BUT THE LOW-LEVEL GRADIENT  
WILL BECOME WEAKER WITH TIME. SPEEDS WILL BE MORE IN THE 10-15 KT  
RANGE TODAY WITH SEAS 2-4 FT, HIGHEST WELL OFFSHORE. TONIGHT, THE  
FLOW BECOMES EVEN LIGHTER AND MORE VARIABLE LATE. SHOWERS AND TSTMS  
MAY INCREASE AFTER MIDNIGHT, AS MOISTURE CONVERGENCE AND INSTABILITY  
PEAK OVER THE WARM ATLANTIC WATERS.  
 
WEDNESDAY THROUGH SUNDAY: BROAD LOW PRESSURE WILL GRADUALLY SHIFT  
OVER THE COASTAL WATERS MID WEEK WHILE A COLD FRONT STALLS NORTH OF  
THE REGION. THE WATERS SHOULD THEN REMAIN BETWEEN HIGH PRESSURE WELL  
OFFSHORE AND A STRENGTHENING TROUGH OF LOW PRESSURE INLAND THROUGH  
FRIDAY. A COLD FRONT WILL THEN APPROACH FROM THE NORTH/NORTHWEST  
FRIDAY NIGHT AND SHIFT OVER THE COASTAL WATERS SATURDAY AND SUNDAY  
BEFORE STALLING OVER OR NEAR SOUTHERN GEORGIA WATERS. AT LEAST  
CHANCES OF SHOWERS AND THUNDERSTORMS ARE FORECAST OVER THE WATERS  
THROUGH LATE WEEK, WHILE NUMEROUS SHOWERS AND THUNDERSTORMS ARE  
POSSIBLE WITH COLD FROPA SATURDAY INTO SUNDAY. CONDITIONS ARE  
EXPECTED TO REMAIN BELOW SMALL CRAFT ADVISORY LEVELS THROUGH THE  
PERIOD. HOWEVER, A SOUTHWEST/SOUTH FLOW COULD GUST AROUND 20 KTS  
FRIDAY NIGHT INTO EARLY SATURDAY UNTIL COLD FROPA OCCURS. SEAS WILL  
GRADUALLY BUILD FROM 2-3 FT TO 3-4 FT THIS WEEKEND AHEAD OF THE  
FRONT, THEN SUBSIDE TO 2-3 FT EARLY NEXT WEEK.  
 

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

 
 

 
NEAR TERM...  
SHORT TERM...DPB  
LONG TERM...DPB  
AVIATION...DPB  
MARINE...DPB  
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab SC Page
The Nexlab GA Page Main Text Page