166  
FXUS62 KCHS 140758  
AFDCHS  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE CHARLESTON SC  
358 AM EDT WED APR 14 2021  
   
SYNOPSIS
 
 
DRY HIGH PRESSURE WILL PREVAIL INTO TONIGHT. A COLD FRONT WILL  
ADVANCE THROUGH THE REGION THURSDAY THEN WILL STALL OFF THE  
SOUTHEAST COAST FRIDAY THROUGH EARLY NEXT WEEK. A SERIES OF LOW  
PRESSURES WILL TRACK ALONG THIS STATIONARY FRONT AND WILL  
PRODUCE PERIODS OF INCLEMENT WEATHER THIS WEEKEND INTO EARLY  
NEXT WEEK. DRIER HIGH PRESSURE WILL BUILD OVER THE REGION  
DURING THE MIDDLE OF NEXT WEEK.  
 

 
   
NEAR TERM /THROUGH TONIGHT/
 
 
SHORTWAVE UPPER RIDGING AND STRONG LOW-LEVEL WARM ADVECTION,  
COMBINED WITH PLENTY OF SUNSHINE, WILL RESULT IN A WARM DAY  
TODAY. BY FAR THE COOLEST AREAS WILL BE ALONG THE BEACHES DUE TO  
A CONSISTENT ONSHORE FLOW OFF THE COOLER ATLANTIC. WE FOLLOWED  
LOCAL CLIMO AND LOW-LEVEL THICKNESS PROGS PRETTY CLOSELY FOR  
INLAND HIGHS, WHICH RESULTS IN 84-87F. A LOW-LEVEL JET WILL  
DEVELOP THIS AFTERNOON AS THE 925 MB RIDGE SHIFTS SOUTHEAST IN  
RESPONSE TO A DIGGING SHORTWAVE FROM THE WEST. WE SHOULD MIX TO  
5,000-7,000 FEET DURING THE AFTERNOON WHICH WILL PRODUCE BREEZY  
CONDITIONS.  
 
A SERIES OF UPPER SHORTWAVES WILL MOVE THROUGH THE AREA TONIGHT,  
THEN A COLD FRONT WILL APPROACH TOWARD DAYBREAK THURSDAY.  
ALTHOUGH LOW-LEVEL MOISTURE ADVECTION WILL BE QUITE LIMITED  
TONIGHT, THERE SHOULD BE ENOUGH FORCING TO PRODUCE AT LEAST  
SCATTERED SHOWERS FROM LATE THIS EVENING THROUGH THE OVERNIGHT  
HOURS. PERSISTENT 5-8 KT SW WINDS WILL RESULT IN A MILD NIGHT  
WITH LOWS IN THE LOW/MID 60S.  
 

 
   
SHORT TERM /THURSDAY THROUGH SATURDAY/
 
 
A COLD FRONT WILL STAFF OFF THE SOUTHEAST COAST, AND WAVES OF LOW  
PRESSURE WILL DEVELOP AND TRACK EAST WITHIN THE ASSOCIATED  
BAROCLINIC ZONE. AS A RESULT, THIS PERIOD WILL FEATURE COOLER  
TEMPERATURES, MOSTLY CLOUDY CONDITIONS AND PERIODS OF SHOWERS. THE  
PROSPECTS FOR MEASURABLE RAINFALL APPEAR GREATEST ACROSS SOUTHERN  
COUNTIES OF THE FORECAST AREA. FARTHER NORTH, INCLUDING THE  
CHARLESTON TRI-COUNTY REGION AND FAR INLAND COUNTIES, THE POTENTIAL  
FOR MEASURABLE RAINFALL REMAINS UNCERTAIN AND WILL DEPEND ON THE  
TRACK, STRENGTH AND MESOSCALE ENVIRONMENT/THUNDERSTORM COVERAGE OF  
EACH WAVE OF LOW PRESSURE THAT WILL PASS TO OUR SOUTH.  
 
THURSDAY: THE COLD FRONT WILL ADVANCE INTO THE REGION, AND A WEAK  
SHORTWAVE TROUGH ALOFT WILL TRACK EAST ACROSS THE SOUTHEAST. WEAK  
FORCING FOR ASCENT AND TRANSPORT OF PWAT VALUES AROUND 1.5 INCH WILL  
SUPPORT SHOWERS. GUIDANCE HAS TRENDED WETTER AS COMPARED WITH RECENT  
DAYS, AND AT LEAST LIKELY POPS ARE IN ORDER SOUTH OF INTERSTATE 16  
FROM MID MORNING TO MID/LATE AFTERNOON. THE NORTHWARD EXTENT OF  
DEEPER MOISTURE/PRECIPITATION REMAINS UNCERTAIN, SO POPS DECREASE  
FARTHER NORTH, AS LOW AS 25-30 PERCENT FAR INLAND/NORTH. HOWEVER, IF  
THE SHORTWAVE TROUGH AMPLIFIES EVEN SLIGHTLY, MORE WIDESPREAD  
SHOWERS COULD SPREAD DEEPER INTO THE FORECAST AREA. INSTABILITY  
COULD SUPPORT ISOLATED THUNDERSTORMS ACROSS SOUTHERN COUNTIES, BUT  
NO SEVERE WEATHER IS EXPECTED. OTHERWISE, HIGH TEMPERATURES WILL  
AVERAGE CLOSE TO NORMAL, IN THE MIDDLE 70S AT MOST LOCATIONS.  
 
THURSDAY NIGHT INTO FRIDAY NIGHT: AS THE COLD FRONT AND ASSOCIATED  
SHORTWAVE TROUGH ALOFT PUSH OFF THE SOUTHEAST COAST, AND THE COLD  
FRONT SHOULD STALL. WEAK HIGH PRESSURE WILL PRESS INTO THE REGION  
AND SHOULD PROVIDE A PERIOD OF RAIN-FREE CONDITIONS, ESPECIALLY  
LATER THURSDAY NIGHT INTO EARLY AFTERNOON FRIDAY. THEN, THE NEXT  
WAVE OF LOW PRESSURE WILL ADVANCE EAST ALONG THE STATIONARY FRONT  
AND COULD SPREAD A FEW SHOWERS INTO FAR SOUTHERN COUNTIES BY  
LATER FRIDAY, WITH AT LEAST ISOLATED/SCATTERED SHOWERS ADVANCING  
INTO THE FORECAST AREA FRIDAY NIGHT. OTHERWISE, COOLER CONDITIONS  
WILL PREVAIL, WITH THURSDAY NIGHT AND FRIDAY NIGHT LOWS MAINLY IN  
THE 50S AND FRIDAY HIGHS IN THE LOWER 70S.  
 
SATURDAY: THE NEXT WAVE OF LOW PRESSURE AND ASSOCIATED DEEP LAYERED  
MOISTURE WILL SPREAD ADDITIONAL SHOWERS INTO THE FORECAST AREA. POPS  
ARE GRADUATED FROM 30-40 PERCENT FAR NORTH/INLAND TO CATEGORICAL  
SOUTH OF I-16, AND GIVEN GUIDANCE TRENDS HIGHER POPS COULD  
EVENTUALLY BE REQUIRED ACROSS A WIDER SWATH OF THE REGION. SATURDAY  
SHOULD ALSO BE THE COOLEST DAY OF THIS PERIOD, WITH TEMPERATURES  
STRUGGLING TO CLIMB ABOUT THE UPPER 60S AT MANY LOCATIONS.  
 

 
   
LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/
 
 
UNSETTLED CONDITIONS/AT LEAST ISOLATED/SCATTERED SHOWERS WILL  
PERSIST INTO TUESDAY AS ADDITIONAL WAVES OF LOW PRESSURE TRACK NEAR  
THE SOUTHEAST COAST. DETAILS REGARDING TIMING, COVERAGE AND  
INTENSITY OF PRECIPITATION EVENTS REMAIN UNCERTAIN, AND FORECASTS  
REMAIN GENERIC. THEN, HIGH PRESSURE SHOULD FINALLY EXPEND INTO  
THE REGION WITH DRIER CONDITIONS BY THE MIDDLE OF NEXT WEEK.  
HIGHS IN THE 70S AND LOWS IN THE 50S SHOULD REMAIN COMMON.  
HOWEVER, GREATER COVERAGE OF SHOWERS COULD RESULT IN COOLER  
DAYTIME TEMPERATURES SUNDAY, MONDAY OR TUESDAY.  
 

 
   
AVIATION /07Z WEDNESDAY THROUGH SUNDAY/
 
 
VFR. GUSTY WINDS EXPECTED THIS AFTERNOON.  
 
EXTENDED AVIATION OUTLOOK: PERIODS OF FLIGHT RESTRICTIONS,  
ESPECIALLY IN LOWER CEILINGS, COULD OCCUR AT ANY TIME THURSDAY  
INTO EARLY NEXT WEEK.  
 

 
   
MARINE
 
 
MODERATE SOUTHERLY FLOW THIS MORNING WILL INCREASE THROUGHOUT  
THE AFTERNOON HOURS AS A POTENT LOW-LEVEL JET DEVELOPS OVER THE  
MARINE AREA. THE CURRENT FORECAST FOR THE CHARLESTON NEARSHORE  
WATERS AND CHARLESTON HARBOR HAVE SUSTAINED WINDS INCREASING TO  
15-20 KT DURING THE MID AFTERNOON WITH SOME HIGHER GUSTS. WE MAY  
VERY WELL NEED SMALL CRAFT ADVISORIES FOR BOTH OF THESE ZONES AT  
SOME POINT THIS AFTERNOON INTO THE EVENING DUE TO 25 KT GUSTS.  
AT THIS JUNCTURE WE HELD OFF ON ISSUING ADVISORIES AS WE'RE  
THINKING THE GUSTS MAY STAY JUST BELOW THAT THRESHOLD. FAIRLY  
POTENT WINDS WILL CONTINUE THROUGH TONIGHT ACROSS THE MARINE  
AREA AS A COLD FRONT APPROACHES THE AREA.  
 
THURSDAY THROUGH MONDAY: AHEAD OF A COLD FRONT, SOUTHWEST WINDS  
15- 20 KNOTS AND AND SEAS 3-5 FEET ARE EXPECTED THURSDAY, AND A  
FEW GUSTS TO 25 KNOTS WILL BE POSSIBLE. SMALL CRAFT ADVISORIES  
COULD EVENTUALLY BE REQUIRED IN SOME AREAS. WINDS WILL SHIFT TO  
THE WEST/NORTHWEST 10-15 KNOTS WITH GUSTS TO 20 KNOTS THURSDAY  
EVENING, THEN WILL VEER TO THE NORTH/NORTHEAST AT SIMILAR SPEEDS  
LATER THURSDAY NIGHT IN TO FRIDAY MORNING. SEAS WILL AVERAGE  
2-4 FEET. THEN, CHANGEABLE WIND DIRECTION SHOULD REMAIN AT OR  
BELOW 15 KNOTS MOST OF THE TIME THIS WEEKEND INTO EARLY NEXT  
WEEK. SEAS WILL AVERAGE 1-3 FEET THROUGH THIS PERIOD. OF NOTE,  
THUNDERSTORMS COULD IMPACT GEORGIA WATERS ANY TIME THIS WEEKEND  
INTO EARLY NEXT WEEK.  
 

 
   
FIRE WEATHER
 
 
RH IS EXPECTED TO DROP TO 27-30% FOR A FEW HOURS THIS AFTERNOON  
ACROSS FAR INLAND SC/GA ZONES. MEANWHILE, AN APPROACHING LOW-  
LEVEL JET AND WARM SURFACE TEMPERATURES WILL RESULT IN DEEP  
MIXING AND SOME GUSTY WINDS. ALTHOUGH WE BUMPED UP OUR WINDS A  
BIT FOR THIS AFTERNOON, WE ARE STILL JUST SHY OF FIRE DANGER  
STATEMENT CRITERIA AND THE DURATION/AREA OF POSSIBLE CRITERIA  
SEEMS A BIT TOO LOW TO JUSTIFY A STATEMENT AT THIS TIME.  
 

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

 
 

 
 
NEAR TERM...JRL  
SHORT TERM...SPR  
LONG TERM...SPR  
AVIATION...JRL/SPR  
MARINE...JRL/SPR  
FIRE WEATHER...  
 
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