003  
FXUS62 KCHS 200840  
AFDCHS  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE CHARLESTON SC  
340 AM EST WED NOV 20 2024  
   
SYNOPSIS
 
 
A STRONG COLD FRONT WILL MOVE THROUGH THE AREA THIS EVENING.  
CANADIAN HIGH PRESSURE WILL BUILD ACROSS THE AREA THURSDAY AND  
WILL REMAIN THE PRIMARY FEATURE THROUGH EARLY NEXT WEEK.  
 

 
   
NEAR TERM /THROUGH TONIGHT/
 
 
TODAY: ALOFT, SHORTWAVE ENERGY WILL SHIFT OFF THE COAST THIS  
MORNING FOLLOWED BY STRENGTHENING ZONAL FLOW ON THE SOUTHEAST  
PERIPHERY OF AN IMPRESSIVE LOW ACROSS THE NORTH-CENTRAL CONUS.  
AT THE SURFACE, THE FORECAST AREA WILL SOLIDLY BE WITHIN THE  
WARM SECTOR AHEAD OF THE MAIN COLD FRONT WHICH WILL PUSH EAST OF  
THE MISSISSIPPI THIS MORNING AND MOVE INTO GEORGIA AND THE  
WESTERN CAROLINAS LATER THIS AFTERNOON. ONGOING EARLY MORNING  
SCATTERED SHOWER ACTIVITY IS BEING FORCED IN AN AREA WITH  
PRECIPITABLE WATER VALUES IN THE 1.5-1.75" RANGE, COINCIDENT  
WITH ISENTROPIC ASCENT IN ADVANCE OF A PRE-FRONTAL TROUGH.  
SHOWER COVERAGE IS EXPECTED TO REMAIN SCATTERED AS IT TRACKS  
EASTWARD THROUGH MID TO LATE MORNING. RAINFALL AMOUNTS SHOULD BE  
ON THE LIGHT SIDE, THOUGH A FEW LOCATIONS COULD PICK UP A TENTH  
OF AN INCH OR SO. RAIN CHANCES ARE EXPECTED TO DIMINISH GREATLY  
FROM WEST TO EAST AROUND MIDDAY AND INTO THE EARLY AFTERNOON,  
SUCH THAT MOST OF THE AREA SHOULD BE RAIN-FREE. THE LAST GASP OF  
SHOWERS WILL LIKELY COME IN THE MID TO LATE AFTERNOON AHEAD OF  
THE PRIMARY FRONT, BUT VERY LITTLE (IF ANY) COVERAGE IS  
EXPECTED. LOW STRATUS IS EXPECTED TO SPREAD ACROSS THE AREA AND  
PERSIST THROUGH THE DAY, RESULTING IN OVERCAST OR MOSTLY CLOUDY  
CONDITIONS. IT WILL BE A WARM DAY, WITH HIGHS IN THE LOW TO MID  
70S.  
 
TONIGHT: THE COLD FRONT IS PROGGED TO ENTER THE FORECAST AREA  
THIS EVENING AND THEN MOVE OFFSHORE BY ROUGHLY MIDNIGHT. MUCH  
DRIER AND COLDER AIR WILL FILTER IN AND THE FORECAST FOR THE  
OVERNIGHT IS DRY. THE MAIN STORY WILL BE STRENGTHENING WINDS IN  
THE COLD ADVECTION. NORTHWEST WINDS WILL FREQUENTLY GUST INTO  
THE 15-20 MPH RANGE IN THE EARLY MORNING HOURS, WITH GUSTS UP TO  
AROUND 25 MPH ALONG THE IMMEDIATE COAST. LOWS ARE FORECAST TO  
BE IN THE LOW TO MID 40S INLAND TONIGHT, WITH MID TO UPPER 40S  
ALONG THE COAST.  
 
LAKE WINDS: A STRONG COLD FRONT WILL SWEEP ACROSS LAKE MOULTRIE  
THIS EVENING, RESULTING IN DEEPENING MIXING PROFILES OVER THE  
LAKE AS COLDER AIR MOVES OVER THE RELATIVELY WARMER LAKE WATERS.  
FREQUENT GUSTS INTO THE 25-30 KNOT RANGE ARE EXPECTED, AND A  
LAKE WIND ADVISORY HAS BEEN ISSUED BEGINNING AT 10PM.  
 

 
   
SHORT TERM /THURSDAY THROUGH SATURDAY/
 
 
MID LEVEL LOW INITIALLY OVER THE GREAT LAKES WILL ROTATE TO THE  
MID-ATLANTIC AND NORTHEAST THURSDAY INTO FRIDAY, WITH THE  
LARGER SCALE TROUGH EXTENDING DOWN THE ENTIRE EAST COAST.  
SURFACE LOW WILL CONTINUE TO MEANDER OVER THE NORTHEASTERN PART  
OF THE COUNTRY WHILE HIGH PRESSURE BEGINS TO BUILD. A TIGHT  
PRESSURE GRADIENT BETWEEN THESE TWO FEATURES WILL SUPPORT GUSTY  
WEST WINDS BOTH DAYS. DESPITE FULL SUNSHINE, COLD AIR MASS WILL  
LIMIT HIGHS TO THE UPPER 50S/LOW 60S ON THURSDAY, THEN MID/UPPER  
50S (~10 DEGREES BELOW NORMAL) FOR FRIDAY. LOWS WILL ALSO BE  
CHILLY, ESPECIALLY FRIDAY NIGHT WHEN TEMPERATURES DIP WELL INTO  
THE 30S INLAND OF THE IMMEDIATE COAST. WHILE THESE TEMPS WOULD  
BE SUPPORTIVE FOR SOME FROST DEVELOPMENT FRIDAY NIGHT/SATURDAY  
MORNING, CURRENT FORECAST KEEPS WINDS A BIT TOO HIGH FOR A  
WIDESPREAD THREAT. WILL BE SOMETHING TO WATCH.  
 
MAIN TROUGH AXIS WILL HAVE EXITED OFF THE COAST BY SATURDAY  
WITH THE PATTERN BEGINNING TO FLATTEN. SURFACE HIGH PRESSURE  
INITIALLY OVER THE MISSISSIPPI RIVER VALLEY WILL TRANSITION TO  
OVER THE SOUTHEAST. COOL AND DRY CONDITIONS WILL PERSIST. HIGHS  
WILL AGAIN BE BELOW CLIMO AROUND 60/LOW 60S.  
 
LAKE WINDS: GUSTY WEST WINDS ARE EXPECTED TO PERSIST OVER LAKE  
MOULTRIE ON THURSDAY, MAINTAINING THE ONGOING LAKE WIND  
ADVISORY. CONDITIONS BECOME MORE MARGINAL FOR THURSDAY NIGHT AND  
FRIDAY, BUT IT'S POSSIBLE THE CURRENT END TIME OF THE ADVISORY  
(00Z FRIDAY) MAY NEED TO BE EXTENDED.  
 

 
   
LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/
 
 
SURFACE HIGH PRESSURE WILL MAINTAIN INFLUENCE OVER THE LOCAL  
WEATHER SUNDAY THROUGH TUESDAY. NOT MUCH GOING ON UPSTAIRS WITH  
RELATIVELY ZONAL FLOW. RAIN-FREE FORECAST IN PLACE WITH WARMING  
TEMPERATURES THROUGH THE PERIOD. MAIN FORECAST CONCERN REMAINS  
THE POTENTIAL FOR FROST LATE SATURDAY NIGHT/EARLY SUNDAY MORNING  
AS IDEAL RADIATIONAL COOLING CONDITIONS ALLOW TEMPERATURES TO  
FALL TO THE MID/UPPER 30S INLAND OF THE COAST. FROST IS  
POSSIBLE, MAINLY OVER FAR INTERIOR LOCATIONS.  
 

 
   
AVIATION /09Z WEDNESDAY THROUGH SUNDAY/
 
 
THE PERIOD BEGINS WITH SOME LIGHT RAIN AND VFR CONDITIONS IN  
PLACE AT KCHS, KJZI, AND KSAV. THERE WILL BE ADDITIONAL SHOWERS  
THROUGH SUNRISE, AND PERHAPS THROUGH ABOUT MID MORNING, BUT NO  
SIGNIFICANT VISIBILITY REDUCTIONS ARE EXPECTED. INSTEAD, THE  
MAIN FORECAST CHALLENGE CONCERNS THE ARRIVAL OF LOW STRATUS AT  
THE TAF SITES AND HOW LONG IT WILL STICK AROUND THROUGH THE DAY.  
THERE IS GOOD MODEL GUIDANCE AGREEMENT THAT THE CEILINGS WILL  
BE IN THE IFR RANGE, BEGINNING AT KSAV FIRST AROUND 10-11Z AND  
THEN REACHING KCHS AND KJZI AROUND 12-13Z. IFR CONDITIONS COULD  
THEN LINGER THROUGH MUCH OF THE DAY, AND THE TAF'S ADVERTISE  
IMPROVEMENT TO MVFR AROUND 19-20Z. SKIES WILL CLEAR OUT AFTER  
00Z AND WINDS WILL TURN NORTHWESTERLY AND BECOME GUSTY (UP TO 20  
KNOTS AT TIMES) BEGINNING AROUND 02-03Z.  
 
EXTENDED AVIATION OUTLOOK: VFR. GUSTY WEST WINDS ARE EXPECTED  
THURSDAY AND FRIDAY.  
 

 
   
MARINE
 
 
TODAY AND TONIGHT: THE FLOW ACROSS THE LOCAL WATERS TODAY WILL  
MOSTLY BE SOUTHWESTERLY AND UP TO AROUND 15 KNOTS. THE BIG  
CHANGE WILL COME THIS EVENING AND OVERNIGHT AS A COLD FRONT  
SWEEPS THROUGH AND BRINGS A STRONG SURGE OF NORTHWEST FLOW.  
WINDS ARE EXPECTED TO RAMP UP BEGINNING LATE THIS EVENING AND  
PEAK THROUGH THE EARLY MORNING HOURS. ACROSS THE NEARSHORE  
WATERS AND CHARLESTON HARBOR, FREQUENT GUSTS UP TO AROUND 30  
KNOTS ARE EXPECTED, WITH A FEW INTO THE LOW 30 KNOT RANGE  
POSSIBLE. SMALL CRAFT ADVISORIES HAVE BEEN ISSUED FOR THESE  
AREAS. FOR THE OUTER GEORGIA WATERS, THERE IS SUFFICIENT  
POTENTIAL FOR A PERIOD OF GALE FORCE WIND GUSTS TO GO WITH A  
GALE WATCH. SEAS WILL RAMP UP IN RESPONSE TO THE WINDS,  
INCREASING TO 3-5 FEET FOR THE NEARSHORE WATERS AND 5-7 FEET FOR  
THE OUTER WATERS.  
 
THURSDAY THROUGH MONDAY: GUSTY WEST WINDS WILL PERSIST OVER THE  
COASTAL WATERS THURSDAY THROUGH FRIDAY NIGHT, MAINTAINING THE  
ONGOING SMALL CRAFT ADVISORIES. FOR THE CHARLESTON HARBOR, GUSTS  
TO 25 KNOTS ARE EXPECTED THURSDAY INTO THURSDAY NIGHT, THEN IT  
LOOKS A BIT MORE MARGINAL FOR FRIDAY. IMPROVEMENT IS EXPECTED  
SATURDAY WITH WINDS AND SEAS REMAINING BELOW ADVISORY LEVELS  
THROUGH MONDAY.  
 

 
   
CHS WATCHES/WARNINGS/ADVISORIES
 
 
GA...NONE.  
SC...LAKE WIND ADVISORY FROM 10 PM THIS EVENING TO 7 PM EST  
THURSDAY FOR SCZ045.  
MARINE...SMALL CRAFT ADVISORY FROM 10 PM THIS EVENING TO 7 AM EST  
FRIDAY FOR AMZ330.  
SMALL CRAFT ADVISORY FROM 10 PM THIS EVENING TO 7 AM EST  
SATURDAY FOR AMZ350-352-354.  
GALE WATCH FROM THIS EVENING THROUGH THURSDAY MORNING FOR  
AMZ374.  
 

 
 

 
 
NEAR TERM...BSH  
SHORT TERM...ETM  
LONG TERM...ETM  
AVIATION...BSH/ETM  
MARINE...BSH/ETM  
 
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