599  
FXUS62 KCHS 241139  
AFDCHS  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE CHARLESTON SC  
739 AM EDT THU MAY 24 2018  
   
SYNOPSIS
 
 
HIGH PRESSURE WILL REMAIN TO THE EAST THROUGH FRIDAY WHILE A  
TROUGH OF LOW PRESSURE LINGERS TO THE WEST. DEVELOPING LOW  
PRESSURE OVER THE GULF OF MEXICO WILL SLOWLY MOVE NORTH TOWARD  
THE CENTRAL GULF COAST THIS WEEKEND, POSSIBLY LINGERING THROUGH  
EARLY NEXT WEEK. THIS PATTERN WILL MAINTAIN HIGHER THAN NORMAL  
RAIN CHANCES ACROSS THE AREA.  
 

 
   
NEAR TERM /THROUGH TONIGHT/
 
 
TODAY: DEEP MOISTURE AND THE MID LEVEL EDDY ACROSS EAST CENTRAL  
GA WILL BE THE STIMULUS FOR ANOTHER ROUND OF DIURNALLY ENHANCED  
CONVECTIVE RAINS ACROSS MUCH OF OUR AREA ALONG AND TO THE WEST  
OF I-95. A SECONDARY MCV WHICH HAD BEEN RESPONSIBLE FOR  
OVERNIGHT CONVECTION TO THE WEST WILL LIKELY BECOME ABSORBED  
WITH THE MID LEVEL VORT MAX THIS AFTERNOON AND THIS FEATURE WILL  
LIKELY BE A SIGNIFICANT FACTOR IN THE PATTERN OF CONVECTIVE  
RAINS LATER TODAY. MID LEVELS ARE WARM AND NOT VERY UNSTABLE  
WITH THE DEEP MOISTURE ENVIRONMENT RESPONSIBLE FOR WEAK  
DOWNDRAFT CAPES. IN FACT, THE UPDRAFT POTENTIAL APPEARS WEAKER  
TODAY, ESPECIALLY WITH MORE CLOUDS TO START OFF THE DAY IN OUR  
WESTERN ZONES. WE HAVE POPS RANGING FROM 65-75 PERCENT ADJACENT  
TO EAST CENTRAL GA WITH LIKELY POPS EXTENDING NORTHWARD TO  
BORDER THE SOUTHERN SC MIDLANDS. LOCATIONS WEST OF A LINE FROM  
LUDOWICI AND SPRINGFIELD GA TO AROUND ALLENDALE SC STAND THE  
BETTER CHANCES OF SEEING BOTH SOME LOCALLY HEAVY DOWNPOURS AND  
SOME THUNDER THIS AFTERNOON. THERE COULD BE SOME LOCALIZED 2-3  
INCH PLUS RAINS SOMEWHERE OVER EASTERN GA BUT THE MESOSCALE  
LOOKS TOO COMPLEX FOR PLACING HIGHEST QPF PRIOR TO CONVECTION  
ONSET. STORM MOTIONS APPEAR QUITE SLOW AND HEAVIEST RAINS WELL  
INLAND WILL LIKELY BE THE RESULT OF MULTICELL MERGERS. VERY  
LOCALIZED EXCESSIVE RAINS CANNOT BE RULED OUT IN OUR FAR WESTERN  
GA ZONES.  
 
IN THE CHARLESTON AREA TODAY, WE LOWERED POPS TO TREND WITH EVEN  
MORE STABLE MID LEVELS AND SOME DISTANCE FROM THE DEEPER  
MOISTURE. MANY OF 00Z MODELS SUGGEST A DRY DAY IS POSSIBLE TO  
THE EAST OF HIGHWAY 17 WITH LOWEST POPS ON THE BEACHES. THE SEA  
BREEZE WILL PROBABLY GENERATE AT LEAST ISOLATED CONVECTIVE  
RAINS. A BACKDOOR FRONT LURKS JUST NORTH WITH CONVECTION MOST  
LIKELY TO DEVELOP FROM THE SOUTHERN PEE DEE INTO THE CENTRAL SC  
MIDLANDS.  
 
HIGHS WILL RANGE FROM THE MID TO UPPER 80S ACROSS THEN ENTIRE  
AREA TODAY WITH FAIRLY LIGHT ONSHORE FLOW.  
 
TONIGHT: NOT MUCH CHANGE TO THE PATTERN. DEEPER MOISTURE LINGERS  
OVER THE REGION WITH EVENING CONVECTION INLAND DWINDLING AND  
A SLIGHT CHANCE FOR SHOWERS MANY AREAS FOR THE OVERNIGHT WITH  
LACK OF ANY INSTABILITY AND ONLY WEAK SPEED CONVERGENCE IN  
THE BOUNDARY LAYER. THERE MAY BE AREAS OF INLAND STRATUS WITH  
SOME LOCALIZED PATCHY FOG NOT OUT OF THE QUESTION. WE DO NOT  
HAVE ANY MENTIONS OF FOG IN THE FORECAST SINCE CLOUDS LOOK TO  
PREVAIL MANY AREAS.  
 

 
   
SHORT TERM /FRIDAY THROUGH SUNDAY/
 
 
ATLANTIC HIGH PRESSURE WILL PREVAIL THROUGH THE END OF THE WEEK.  
MEANWHILE LOW PRESSURE IS EXPECTED TO SLOWLY ORGANIZE OVER THE GULF  
OF MEXICO AND MOVE NORTH TOWARD THE GULF COAST. THE TRACK AND  
STRENGTH OF THIS LOW IS A BIT UNCERTAIN BUT MODELS GENERALLY AGREE  
THE LOW WILL MAKE LANDFALL ANYWHERE FROM AROUND NEW ORLEANS, LA TO  
APALACHICOLA, FL. EITHER WAY A TROPICAL AIR MASS WILL REMAIN IN  
PLACE WITH RAIN CHANCES GENERALLY STAYING ABOVE NORMAL, MOSTLY  
DURING THE AFTERNOON AND EVENING EACH DAY. IN GENERAL WE THINK THE  
HIGHEST CHANCES WILL BE INLAND NEAR THE BETTER MOISTURE, INSTABILITY  
AND FORCING, ESPECIALLY SUNDAY. HOWEVER THERE IS SOME UNCERTAINTY  
FOR SATURDAY AS THERE MAY BE A BREAK IN THE RAIN. SOME SPOTS WILL  
LIKELY PICK UP OVER AN INCH THROUGH THE PERIOD. NO SIGNIFICANT  
FLOODING OR SEVERE WEATHER IS ANTICIPATED AT THIS TIME. TEMPERATURES  
WILL GENERALLY BE ABOVE NORMAL EXCEPT FOR SUNDAY WHEN IT WILL  
LIKELY BE BELOW NORMAL GIVEN THE ABUNDANT RAIN COVERAGE.  
 

 
   
LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/
 
 
NOT MUCH PATTERN CHANGE THROUGH THE PERIOD WITH DEEP LOW PRESSURE  
PERSISTING TO THE WEST AND ATLANTIC HIGH PRESSURE TO THE EAST. THIS  
WILL MAINTAIN A TROPICAL AIR MASS ACROSS THE AREA AND LEAD TO HIGHER  
THAN NORMAL RAIN CHANCES, WITH NOT MUCH MORE PREFERENCE FOR HIGHER  
RAIN CHANCES DURING THE DAY THAN AT NIGHT. TEMPERATURES SHOULD  
STAY NEAR TO ABOVE NORMAL.  
 

 
   
AVIATION /12Z THURSDAY THROUGH MONDAY/
 
 
KCHS: MAINLY VFR. ISOLATED SHOWERS POSSIBLE THIS MORNING WITH  
SEA BREEZE CONVECTION MORE LIKELY INLAND BY THIS AFTERNOON.  
 
KSAV: WE HAVE INTRODUCED A TEMPO SHRA TO TREND TOWARD MORE  
CONFIDENCE IN SCATTERED CONVECTIVE RAINS CLOSER TO DEEPEST  
MOISTURE ANCHORED OVER THE EASTERN HALF OF GA. A FEW TSTMS  
MAY DEVELOP AROUND THE AREA LATER TODAY. TONIGHT, SHOWER CHANCES  
TO SMALL FOR TAF MENTIONS AT THIS TIME WITH LOW CLOUDS POSSIBLE  
INLAND FROM THE TERMINAL LATE (ESPECIALLY IF SOME BREAKS IN THE  
CLOUDS OCCUR).  
 
EXTENDED AVIATION OUTLOOK: A PERSISTENT TROPICAL AIR MASS WILL LEAD  
TO HIGHER THAN NORMAL RAIN CHANCES INTO EARLY NEXT WEEK, 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
 
 
A LIGHT SOUTHERLY FLOW EARLY ON TODAY WILL BECOME MORE ONSHORE  
WITH A VERY WEAK COASTAL TROUGH DEVELOPING TONIGHT ALONG THE SC  
COAST. WINDS WILL BE ON THE WEAK SIDE, LESS THAN 15 KT AND  
BELOW 10 KT MUCH OF THE TIME. SEAS 2 TO 3 FT THROUGH EARLY  
FRIDAY.  
 
FRIDAY THROUGH TUESDAY: THE AREA IS EXPECTED TO REMAIN ON THE  
WESTERN EDGES OF ATLANTIC HIGH PRESSURE AS A LOW PRESSURE SYSTEM IS  
EXPECTED TO DEVELOP OVER THE GULF OF MEXICO AND TRACK NORTH TOWARD  
THE GULF COAST. DEPENDING ON THE STRENGTH AND TRACK OF THE LOW WILL  
DETERMINE HOW MUCH OF A WIND/SEA INCREASE THERE WILL BE LOCALLY SO  
MARINERS SHOULD PAY CLOSE ATTENTION TO THE FORECAST FOR THIS WEEKEND  
INTO EARLY NEXT WEEK AS SMALL CRAFT ADVISORIES WILL BE POSSIBLE FOR  
SOME OR ALL OF THE MARINE AREA.  
 

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

 
 

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