493  
FXUS62 KCHS 190209  
AFDCHS  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE CHARLESTON SC  
1009 PM EDT MON MAR 18 2019  
   
SYNOPSIS
 
 
A DRY COLD FRONT WILL MOVE THROUGH TONIGHT, FOLLOWED BY HIGH  
PRESSURE. A TROUGH WILL DEVELOP OFFSHORE WEDNESDAY THEN MOVE  
NORTHEAST AWAY FROM THE AREA. HIGH PRESSURE WILL THEN PREVAIL  
THROUGH EARLY NEXT WEEK.  
 

 
   
NEAR TERM /UNTIL 6 AM TUESDAY MORNING/
 
 
THE DRY COLD FRONT WILL PUSH INTO THE OCEAN BY MIDNIGHT NORTH  
AND BEFORE 1 OR 2 AM SOUTH, ALLOWING FOR STRONGER HIGH PRESSURE  
TO BUILD OUT OF THE ALLEGHENY PLATEAU REGION OF OHIO AND WEST  
VIRGINIA. A STEADY SUPPLY OF COLDER AIR WILL FILTER IN THROUGH  
THE NIGHT, ALLOWING FOR THE H85 0C ISOTHERM TO PENETRATE TO NEAR  
THE NORTHERN TIER OF THE CWFA BY DAYBREAK. THE COLD ADVECTION  
WILL BE OFFSET SOMEWHAT BY VARYING AMOUNTS AND THICKNESS OF  
CIRRIFORM CLOUDS DUE TO THE UPPER JET THAT MOVES THROUGH THE  
AREA. BECAUSE OF THESE CLOUDS WE CONTINUE TO SLOW OUR DECLINE IN  
HOURLY TEMPS FROM PREVIOUS FORECASTS, AND HAVE ALSO KEPT MORE  
CLOUD COVER THAN EARLIER.  
 
THERE IS TOO MUCH MIXING FOR ANY FROST, ALTHOUGH LOWS WILL GET  
DOWN TO THE UPPER 30S AND LOWER 40S MOST COMMUNITIES INLAND FROM  
US-17 AND THE MID AND UPPER 40S ON THE BARRIER ISLANDS AND IN  
DOWNTOWN CHARLESTON AND DOWNTOWN SAVANNAH.  
 
LAKE WINDS: AS COLDER AIR MOVES ACROSS LAKE MOULTRIE THROUGH  
THE NIGHT, AND STEADY ISALLOBARIC PRESSURE RISES SET IN, BETTER  
MIXING WILL DEVELOP. WE HAVE N-NE WINDS AT A SOLID 15-20 KT, OR  
JUST SHY OF ISSUING A LAKE WIND ADVISORY.  
 

 
   
SHORT TERM /6 AM TUESDAY MORNING THROUGH THURSDAY/
 
 
COOL AND DRY HIGH PRESSURE WILL PERSIST NORTH OF THE AREA  
TUESDAY INTO WEDNESDAY, KEEPING HIGHS IN THE LOW TO MID 60S AND  
LOWS IN THE UPPER 30S TO LOWER 40S. MOSTLY CLEAR SKIES ARE  
EXPECTED ASIDE FROM POSSIBLE STRATOCU ON WEDNESDAY AS A WEAK  
COASTAL TROUGH DEVELOPS OFF THE SC COAST.  
 
A CONSIDERABLE WARM-UP IS IN STORE FOR THURSDAY AS THE COLD AIR  
ADVECTION DIMINISHES AND A MODERATE DOWNSLOPE FLOW SETS UP. HIGH  
TEMPS WILL CLIMB INTO THE LOWER 70S.  
 

 
   
LONG TERM /THURSDAY NIGHT THROUGH MONDAY/
 
 
A RATHER QUIET WEATHER PATTERN IS EXPECTED. STRONG CONTINENTAL HIGH  
PRESSURE WILL PREVAIL ACROSS THE REGION THROUGH THE WEEKEND. MODELS  
THEN HINT AT A SYSTEM APPROACHING FROM THE WEST LATE SUNDAY.  
 

 
   
AVIATION /02Z TUESDAY THROUGH SATURDAY/
 
 
VFR THROUGH 00Z WEDNESDAY. N-NE WINDS WILL INCREASE BEHIND A  
COLD FRONT OVERNIGHT AND CONTINUE GUSTY AT TIMES THROUGH MUCH OF  
TUESDAY S STRONG HIGH PRESSURE BUILDS INTO THE AREA.  
 
EXTENDED AVIATION: VFR.  
 

 
   
MARINE
 
 
THE SURFACE PRESSURE GRADIENT WILL TIGHTEN TONIGHT AS HIGH  
PRESSURE BUILDS INTO THE AREA BEHIND A COLD FRONT THAT MOVES  
INTO THE WATERS AROUND MIDNIGHT NORTH AND BEFORE 2 AM SOUTH.  
THIS WILL LEAD TO ELEVATED N AND NE WINDS AS HIGH AS 20-25 KT  
WITH STRONGER GUSTS IN THE ATLANTIC OVERNIGHT. SMALL CRAFT  
ADVISORIES REMAIN IN EFFECT FOR ALL WATERS WITH THE EXCEPTION  
OF THE CHARLESTON HARBOR. WIND GUSTS IN THE HARBOR WILL GET  
CLOSE TO ADVISORY CRITERIA AFTER 06Z, BUT THE FREQUENCY LOOKS  
LIMITED ENOUGH NOT TO RAISE AN ADVISORY. WE WILL CONTINUE TO  
EVALUATE WITH FUTURE FORECAST ISSUANCES. SEAS WILL BUILD TO 4-6  
FEET BY DAYBREAK FOR THE NEARSHORE WATERS, 5-7 FT IN THE OFFSHORE  
ZONE.  
 
A RATHER PERSISTENT STRONG NORTHEAST GRADIENT IS EXPECTED  
TUESDAY INTO WEDNESDAY AS HIGH PRESSURE REMAINS NORTH OF THE  
WATERS. SMALL CRAFT ADVISORIES EXPECTED TO CONTINUE INTO AT  
LEAST WEDNESDAY FOR ALL WATERS OUTSIDE CHARLESTON HARBOR.  
LINGERING 6 FT OR GREATER SEAS WILL KEEP THE CHARLESTON  
NEARSHORE WATERS IN ADVISORY TERRITORY THROUGH WEDNESDAY EVENING  
AND THE OFFSHORE GA WATERS THROUGH THURSDAY AFTERNOON.  
 
A PERIOD OF MODERATE OFFSHORE WINDS IS THEN EXPECTED THURSDAY  
INTO FRIDAY AS HIGH PRESSURE BUILDS FROM THE WEST. AT THIS POINT  
IT APPEARS WINDS/SEAS WILL REMAIN BELOW ADVISORY LEVELS EXCEPT  
FOR THE AFOREMENTIONED SCA FOR THE OFFSHORE GA WATERS.  
 

 
   
TIDES/COASTAL FLOODING
 
 
THE COMBINATION OF THE PERIGEE AND FULL MOON MIDWEEK ALONG WITH  
MODERATE TO STRONG NORTHEAST WINDS THROUGH WEDNESDAY WILL  
RESULT IN ELEVATED TIDES. COASTAL FLOOD ADVISORIES FOR MINOR OR  
MAYBE MODERATE FLOODING ARE LIKELY WITH EACH HIGH TIDE TUESDAY,  
WEDNESDAY, AND MAYBE THURSDAY IF THE ANOMALIES LINGER.  
 

 
   
CHS WATCHES/WARNINGS/ADVISORIES
 
 
GA...NONE.  
SC...NONE.  
MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EDT WEDNESDAY FOR AMZ352-354.  
SMALL CRAFT ADVISORY UNTIL 9 PM EDT THURSDAY FOR AMZ374.  
SMALL CRAFT ADVISORY UNTIL MIDNIGHT EDT WEDNESDAY NIGHT FOR  
AMZ350.  
 

 
 

 
NEAR TERM...  
SHORT TERM...JRL  
LONG TERM...  
AVIATION...  
MARINE...  
TIDES/COASTAL FLOODING...  
 
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