419  
FXUS62 KCHS 192304  
AFDCHS  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE CHARLESTON SC  
704 PM EDT MON APR 19 2021  
   
SYNOPSIS
 
 
WEAK HIGH PRESSURE WILL REMAIN OVER THE REGION EARLY THIS WEEK.  
THEN, A COLD FRONT WILL SWEEP ACROSS THE REGION ON WEDNESDAY.  
HIGH PRESSURE WILL THEN RETURN FOR LATE WEEK. LOW PRESSURE WILL  
IMPACT THE AREA OVER THE WEEKEND.  
 

 
   
NEAR TERM /UNTIL 6 AM TUESDAY MORNING/
 
 
THERE HAS BEEN A LITTLE RECOVERY IN DEW POINTS, WHICH IS  
COINCIDING WITH WINDS DIMINISHING. THESE CHANGES HAVE BEEN  
INCORPORATED INTO THE GRIDS, BUT THE FORECAST IS ESSENTIALLY  
UNCHANGED FROM EARLIER.  
 
PREVIOUS DISCUSSION...  
AS OF 330 PM: THE CENTER OF DRY HIGH PRESSURE WILL PUSH OVER THE  
REGION TONIGHT. SFC WINDS SHOULD VEER FROM NW LATE THIS AFTERNOON TO  
NE AROUND MIDNIGHT, THE SE BY DAYBREAK TUESDAY. A WEAK LOW IS  
FORECAST TO TRACK OVER THE FL PENINSULA LATE TONIGHT, RESULTING IN  
SCATTERED HIGH CLOUDS TO ARRIVE FROM THE SOUTH. THE COMBINATION  
OF DRY BOUNDARY LAYER CONDITIONS, LIGHT WINDS, AND LATE ARRIVAL  
OF HIGH CLOUDS SHOULD YIELD NEAR NORMAL LOWS TONIGHT. MIN  
TEMPERATURES ARE FORECAST TO RANGE FROM THE LOW 50S INLAND TO  
NEAR 60 ALONG THE COAST.  
 

 
   
SHORT TERM /6 AM TUESDAY MORNING THROUGH THURSDAY/
 
 
AS HIGH PRESSURE MOVES AWAY FROM THE AREA AND INTO THE ATLANTIC ON  
TUESDAY, LOW PRESSURE WILL MOVE OFF THE COAST OF FLORIDA IN AN  
EASTWARD DIRECTION ACROSS THE ATLANTIC. WHILE THERE WILL BE  
INCREASED ISENTROPIC LIFT AND PWATS WILL BE AROUND AN INCH, ANY  
SHOWER ACTIVITY WILL LIKELY REMAIN JUST ALONG THE COAST AND ACROSS  
THE COASTAL WATERS. MOST INLAND AREAS SHOULD REMAIN RAIN-FREE. HIGH  
TEMPERATURES WILL BE IN THE 70S. THEREAFTER, A SURFACE LOW WILL MAKE  
ITS WAY ACROSS THE OHIO RIVER VALLEY OVERNIGHT TUESDAY. LOW  
TEMPERATURES WILL BE IN THE MID TO UPPER 50S INLAND AND LOW 60S JUST  
ALONG THE COAST. THEN ON WEDNESDAY, A DRY COLD FRONT ASSOCIATED WITH  
THE LOW WILL THEN MOVE THROUGH THE AREA AND AS THE PRESSURE GRADIENT  
TIGHTENS, WINDS WILL BECOME GUSTY. THOUGH, THE DAY SHOULD BE MOSTLY  
SUNNY WITH HIGH TEMPERATURES IN THE UPPER 70S TO LOW 80S. LOWS WILL  
BE IN LOW TO UPPER 40S INLAND WITH LOW 50S JUST ALONG THE COAST DUE  
TO COLD AIR ADVECTION. FOR THURSDAY, HIGH PRESSURE WILL GENERALLY  
PREVAIL AND IT WILL BE A NICE, SUNNY DAY. HIGH TEMPERATURES WILL BE  
IN THE MID 60S TO LOW 70S INLAND AND LOW 60S JUST ALONG THE COAST.  
 
LAKE WINDS: WINDS AHEAD AND BEHIND A COLD FRONT WILL BECOME QUITE  
GUSTY DUE TO A TIGHTENING PRESSURE GRADIENT. A LAKE WIND ADVISORY  
COULD BE NEEDED FOR LAKE MOULTRIE.  
 

 
   
LONG TERM /THURSDAY NIGHT THROUGH MONDAY/
 
 
OVERNIGHT THURSDAY, HIGH PRESSURE WILL PREVAIL AND LOW TEMPERATURES  
WILL BE IN THE MID 40S TO LOW 50S INLAND AND MID 50S JUST ALONG THE  
COAST. THEN ON FRIDAY, ANOTHER DRY DAY AND MOSTLY SUNNY SKIES IS  
EXPECTED. THOUGH, AS A DEEP-LAYERED TROUGH MOVES CLOSER TO THE AREA  
FROM THE WEST, CLOUD COVER WILL SLIGHTLY INCREASE. HIGH TEMPERATURES  
WILL BE IN THE 70S WITH LOWS IN THE MID TO UPPER 50S INLAND AND LOW  
TO MID 60S JUST ALONG THE COAST.  
 
WHILE THERE IS STILL UNCERTAINTY WITHIN THE MODELS FOR TIMING AND  
LOCATION OF THE APPROACHING LOW PRESSURE, RAIN CHANCES WILL INCREASE  
ON SATURDAY INTO SUNDAY MORNING. THE BEST CHANCE OF RAIN LOOKS TO BE  
DURING SATURDAY AFTERNOON INTO THE OVERNIGHT. BY DAYBREAK, THE LOW  
PRESSURE SHOULD BE COMFORTABLY TO THE NORTHEAST AND THE COLD FRONT  
SHOULD BE OFFSHORE. THOUGH, A SECONDARY COLD FRONT COULD THEN MOVE  
THROUGH THE REGION. THE MAJORITY OF SUNDAY AND ALL OF MONDAY SHOULD  
BE RAIN-FREE AS HIGH PRESSURE QUICKLY BUILDS INTO THE AREA. HIGH  
TEMPERATURES WILL BE IN THE MID TO UPPER 70S TO LOW 80S EACH DAY.  
LOW TEMPERATURES WILL BE IN THE 50S INLAND AND LOW 60S JUST ALONG  
THE COAST.  
 

 
   
AVIATION /00Z TUESDAY THROUGH SATURDAY/
 
 
VFR THROUGH 00Z WEDNESDAY. SE WINDS WILL BECOME A LITTLE GUSTY  
IN WAKE OF THE SEA BREEZE TUESDAY AFTERNOON.  
 
EXTENDED AVIATION OUTLOOK: MAINLY VFR. GUSTY WINDS LIKELY ON  
WEDNESDAY, THEN AGAIN ON SATURDAY. FLIGHT RESTRICTIONS WILL ALSO BE  
POSSIBLE ON SATURDAY DUE TO SHOWERS/THUNDERSTORMS.  
 

 
   
MARINE
 
 
HIGH PRESSURE WILL BUILD OVER THE REGION TONIGHT. AS PRESSURES RISE  
FROM THE NE, A BIT OF WIND SURGE WILL PUSH FROM THE NE TO SW  
ACROSS THE COASTAL WATERS TONIGHT. N AND NW WINDS WILL VEER  
AROUND TO THE ENE, AND STRENGTHEN TO 10 TO 15 KTS WITH GUSTS TO  
20 KTS AFTER MIDNIGHT OVER THE MARINE ZONES OUTSIDE THE CHS  
HARBOR. SEAS WILL INCREASE SLIGHTLY FROM 1-2 FT THIS EVENING TO  
2 FT ACROSS MOST AREAS BY DAYBREAK.  
 
TRANQUIL MARINE CONDITIONS EXPECTED TO LAST THROUGH EARLY WEDNESDAY.  
THEN, AHEAD OF AN APPROACHING COLD FRONT, WINDS WILL INCREASE BY  
WEDNESDAY AFTERNOON TO 15-20 KNOTS AND SMALL CRAFT ADVISORIES COULD  
BE NEEDED FOR WINDS AND SEAS THROUGH THURSDAY MORNING. HIGH PRESSURE  
WILL THEN BUILD INTO THE AREA AND TRANQUIL MARINE CONDITIONS SHOULD  
RETURN THROUGH LATE FRIDAY. ANOTHER ROUND OF SMALL CRAFT ADVISORIES  
COULD BE NEEDED OVER THE WEEKEND DUE TO ANOTHER APPROACHING COLD  
FRONT.  
 

 
   
FIRE WEATHER
 
 
A COMBINATION OF GUSTY WINDS, LOW RELATIVE HUMIDITY, AND DRY FUELS  
COULD PRODUCE HAZARDOUS FIRE CONDITIONS WEDNESDAY AFTERNOON/EARLY  
EVENING. NEAR CRITICAL RELATIVE HUMIDITY VALUES WILL PERSIST  
THURSDAY AND FRIDAY AFTERNOONS, ALTHOUGH WINDS WILL REMAIN LESS THAN  
15 MPH.  
 

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

 
 

 
 
NEAR TERM...  
SHORT TERM...RAD  
LONG TERM...RAD  
AVIATION...  
MARINE...  
FIRE WEATHER...  
 
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