654  
FXUS62 KCHS 221548  
AFDCHS  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE CHARLESTON SC  
1148 AM EDT TUE MAY 22 2018  
   
SYNOPSIS
 
 
THE REGION WILL REMAIN IN A WARM AND MUGGY AIR MASS BETWEEN  
ATLANTIC HIGH PRESSURE TO THE EAST AND LOW PRESSURE TO THE WEST  
INTO EARLY NEXT WEEK.  
 

 
   
NEAR TERM /UNTIL 6 PM THIS EVENING/
 
 
THE CONVECTIVE PATTERN IS EVOLVING AS EXPECTED WITH THE GREATEST  
CONCENTRATION OF SHOWERS/TSTMS OCCURRING OVER SOUTHEAST GEORGIA  
INTO FAR SOUTHERN SOUTH CAROLINA. NEAR TERM POPS WERE ADJUSTED  
UPWARDS TO 80-90% ALONG THE GEORGIA COAST, INCLUDING THE  
SAVANNAH METRO AREA, FOR THE NEXT FEW HOURS BASED ON SHORT TERM  
RADAR AND MODEL TRENDS. POPS WERE ALSO LOWERED SLIGHTLY FOR THE  
CHARLESTON METRO AREA AS THE SEA BREEZE IS ALREADY MOVING  
INLAND WEST THE HIGHWAY 17 CORRIDOR, WHICH SHOULD HELP DIMINISH  
THE RISK FOR MEASURABLE RAINFALL. MINOR ADJUSTMENTS WERE MADE TO  
HOURLY TEMPERATURES PER LATEST OBSERVATIONS. THERE SHOULD BE  
ENOUGH SUN AND BREAKS BETWEEN THE CONVECTIVE CLUSTERS FOR  
TEMPERATURES TO MAKE THE CURRENT HIGH TEMPERATURE FORECAST SO NO  
CHANGES WERE MADE THERE AT THIS TIME.  
 
A FAIRLY ACTIVE, WET DAY IS EXPECTED FOR MUCH OF THE DAY AS THE  
REGION WILL REMAIN PINNED BETWEEN BROAD MID-LEVEL TROUGHINESS  
EXTENDING ACROSS THE DEEP SOUTH INTO FLORIDA AND SUBTROPICAL  
HIGH PRESSURE CENTERED WELL OFFSHORE. MOISTURE BEING ADVECTED  
NORTHWARD OUT OF THE WESTERN CARIBBEAN WILL REMAIN IN PLACE  
TODAY WITH PWATS SURGING AS HIGH AS 1.90 INCHES AT TIMES.  
FORECAST AND OBSERVED SOUNDINGS SHOW FAIRLY LOW CONVECTIVE  
TEMPERATURES SO WITH DEEP, TROPICAL MOISTURE IN PLACE AIDED  
BY SOME WEAK DIFLUENCE ALOFT ASSOCIATED WITH AN H25 SHEAR AXIS,  
EXPECT SCATTERED TO NUMEROUS SHOWERS AND SOME TSTMS TO IMPACT  
MUCH OF SOUTHEAST SOUTH CAROLINA AND SOUTHEAST GEORGIA THROUGH  
SUNSET. IT APPEARS THAT THE DEEPEST BAND OF MOISTURE WILL SETUP  
ACROSS SOUTHEAST GEORGIA SO THIS SHOULD BE WHERE THE GREATEST  
RAIN COVERAGE SHOULD OCCUR, ESPECIALLY THE AFTERNOON SEA BREEZE  
BEGINS ITS INLAND TREK. SUBTROPICAL RIDGING LOOKS TO HOLD THE  
STRONGEST OVER THE CHARLESTON METRO AREA UP INTO EASTERN  
BERKELEY AND UPPER CHARLESTON COUNTIES SO RAIN CHANCES WILL BE  
CONSIDERABLY LESS THERE, WHICH MATCHES THE LATEST TRENDS NOTED  
IN THE VARIOUS CAMS. LOCALLY HEAVY RAINFALL ALONG WITH MINOR  
FLOODING OF LOW LYING AND POOR DRAINAGE AREAS WILL BE THE  
PRIMARY HAZARDS TODAY.  
 
FOR THE MORNING UPDATE, WILL INCREASE POPS TO 70% ACROSS MUCH  
OF INTERIOR SOUTHEAST GEORGIA AND EXPAND LIKELY POPS UP TO 60%  
EASTWARD INTO THE WALTERBORO AND BEAUFORT AREAS. POPS WILL THEN  
DROP OFF QUICKLY INTO THE 20-30% RANGE OVER EASTERN BERKELEY AND  
UPPER CHARLESTON COUNTIES. ALSO LOWERED HIGHS 1-2 DEGS ACROSS  
SOUTHEAST GEORGIA WHERE EXTENSIVE CLOUD COVER AND SHOWER  
ACTIVITY SHOULD LIMIT TEMPERATURES.  
 

 
   
SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY/
 
 
TONIGHT: DIURNAL SHOWERS AND ISOLATED THUNDERSTORMS ARE FORECAST TO  
GRADUALLY DISSIPATE THROUGH THE EVENING AND OVERNIGHT HOURS. I WILL  
FORECAST SCHC POPS FOR MOST AREAS, SLIGHTLY GREATER OVER THE MARINE  
AREAS. USING A BLEND OF MOS, I WILL FORECAST LOW TEMPS FROM LOW 70S  
ACROSS THE BEACHES TO THE UPPER 60S INLAND.  
 
WEDNESDAY THROUGH FRIDAY: THE AREA WILL REMAIN BETWEEN ATLANTIC  
HIGH PRESSURE TO THE EAST AND LOW PRESSURE TO THE WEST. A COLD  
FRONT WILL APPROACH FROM THE NORTH WEDNESDAY NIGHT BEFORE  
STALLING OUT JUST NORTH OF THE AREA. THIS PATTERN WILL MAINTAIN  
THE TROPICAL AIR MASS IN PLACE AND LEAD TO HIGHER THAN NORMAL  
RAIN CHANCES, ESPECIALLY EACH AFTERNOON AND EVENING. IN GENERAL  
WE THINK THE HIGHEST CHANCES WILL BE INLAND NEAR THE BETTER  
MOISTURE, INSTABILITY AND FORCING. SOME SPOTS COULD PICK UP OVER  
AN INCH THROUGH THE PERIOD. NO SIGNIFICANT FLOODING OR SEVERE  
WEATHER IS ANTICIPATED AT THIS TIME. TEMPERATURES WILL GENERALLY  
BE NEAR TO ABOVE NORMAL, ESPECIALLY LOWS.  
 

 
   
LONG TERM /FRIDAY NIGHT THROUGH MONDAY/
 
 
NOT MUCH PATTERN CHANGE LATE THIS WEEK INTO EARLY NEXT WEEK WITH  
HIGH PRESSURE REMAINING TO THE EAST AND AND LOW PRESSURE TO THE  
WEST. WILL BE WATCHING FOR POTENTIAL TROPICAL CYCLONE DEVELOPMENT IN  
THE SOUTH-CENTRAL GULF OF MEXICO. MODELS HAVE BEEN FAIRLY AGREEABLE  
LATELY THAT THE LOW WILL TRACK TOWARD THE NORTH-CENTRAL GULF COAST  
REGION THIS WEEKEND. THIS PATTERN WILL CONTINUE TO MAINTAIN A  
TROPICAL AIR MASS ACROSS SOUTHEAST SC/GA AND LEAD TO HIGHER THAN  
NORMAL RAIN CHANCES. TEMPERATURES SHOULD STAY NEAR TO ABOVE  
NORMAL.  
 

 
   
AVIATION /16Z TUESDAY THROUGH SATURDAY/
 
 
KCHS: VFR. SHOWERS/TSTMS SHOULD REMAIN WEST OF THE TERMINAL.  
 
KSAV: SHOWERS/TSTMS SHOULD BE AT/AROUND THE TERMINAL AT THE  
BEGINNING OF THE 18Z TAF PERIOD. ACTIVITY SHOULD MOVE QUICKLY  
WEST AND NORTHWEST OF THE TERMINAL BY 19-20Z. OTHERWISE, VFR.  
 
EXTENDED AVIATION OUTLOOK: A PERSISTENT TROPICAL AIR MASS WILL LEAD  
TO HIGHER THAN NORMAL RAIN CHANCES THROUGH THE WEEKEND, MAINLY EACH  
AFTERNOON. THUNDER CHANCES WILL BE LOW HOWEVER GIVEN THE LIMITED  
INSTABILITY. SOME RESTRICTIONS WILL ALSO BE POSSIBLE FROM MORNING  
LOW CLOUDS AND/OR FOG AS WELL.  
 

 
   
MARINE
 
 
LARGE HIGH PRESSURE CENTERED OVER BERMUDA WILL REMAIN OVER THE  
REGION THROUGH TONIGHT. SOUTHEAST WINDS WILL CONTINUE THROUGH TODAY  
AND TONIGHT, SPEEDS REMAINING BETWEEN 10-13 KTS. WAVE HEIGHTS ARE  
FORECAST TO RANGE FROM 2-3 FT WITHIN 20 NM TO 4-5 FT BEYOND 20 NM.  
 
WEDNESDAY THROUGH SUNDAY: THE AREA WILL REMAIN BETWEEN LOW PRESSURE  
TO THE WEST AND HIGH PRESSURE TO THE EAST. A TROPICAL CYCLONE MAY  
DEVELOP IN THE CENTRAL GULF OF MEXICO LATER THIS WEEK BUT MODELS ARE  
IN GOOD AGREEMENT IT WILL REMAIN FAR ENOUGH AWAY TO NOT HAVE REALLY  
SIGNIFICANT IMPACTS LOCALLY. HOWEVER, DO EXPECT AN INCREASE IN WINDS  
AND SEAS LATER THIS WEEK AND WE COULD SEE ADVISORY CONDITIONS THIS  
WEEKEND.  
 

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

 
 

 
 
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