758  
FXUS62 KCHS 232346  
AFDCHS  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE CHARLESTON SC  
632 PM EST SAT FEB 23 2019  
   
SYNOPSIS
 
 
A WARM FRONT WILL LIFT NORTH THROUGH THE FORECAST AREA TONIGHT.  
THEN ON SUNDAY, A COLD FRONT WILL SWEEP THROUGH FROM THE WEST  
AND MOVE OFFSHORE IN THE EVENING. HIGH PRESSURE IS EXPECTED TO  
PREVAIL INTO THE MIDDLE OF NEXT WEEK AND AN AREA OF LOW  
PRESSURE COULD PASS OFF THE COAST LATE IN THE WEEK.  
 

 
   
NEAR TERM /UNTIL 6 AM SUNDAY MORNING/
 
 
A COMPLEX SURFACE PATTERN IS IN PLACE THIS EVENING AS INSITU  
COLD AIR DAMMING HOLDS ACROSS MUCH OF NORTH CAROLINA, SOUTH  
CAROLINA AND INTO GEORGIA. 23/23Z SURFACE ANALYSIS PLACED  
A STATIONARY WEDGE FRONT EXTENDING FROM JUST OFFSHORE OF THE  
CHARLESTON COUNTY COAST TO NEAR HILTON HEAD, THEN ARCING BACK  
INLAND ALONG THE I-16 CORRIDOR INTO CENTRAL GEORGIA. NORTH OF  
THE WEDGE FRONT, FOG/STRATUS WITH AREAS OF DRIZZLE ARE COMMON,  
WHILE SOUTH OF THE FRONT, MUCH WARMER CONDITIONS ARE FOUND WITH  
LITTLE IN THE WAY OF FOG/DRIZZLE, EXCEPT ALONG THE IMMEDIATE  
GEORGIA AND FAR SOUTHERN SOUTH CAROLINA COAST WHERE SEA FOG IS  
PRESENT. FARTHER SOUTH, A SHARPENING WARM FRONT EXTENDED FROM  
ROUGHLY JACKSONVILLE, FLORIDA, TO ALMA, GA, THEN EXTENDING  
NORTHWEST THROUGH CENTRAL INTO WEST-CENTRAL GEORGIA NEAR  
COLUMBUS, GA. THE INLAND AND NORTHWARD PROGRESSION OF THESE  
FEATURES WILL MAKE FOR A RATHER DIFFICULT OVERNIGHT FORECAST  
WITH A NUMBER OF FORECAST CHALLENGES TO ADDRESS.  
 
RAIN: KCLX/KVAX RADARS SHOW ISOLATED SHOWERS DEVELOPING JUST  
SOUTH OF THE ALTAMAHA RIVER. THIS ACTIVITY APPEARS TO CORRELATED  
TO A SMALL AREA OF ENHANCED ISENTROPIC ASSENT ALONG THE 305K  
ISOSURFACE FORMING JUST NORTH OF THE SYNOPTIC WARM FRONT. THE  
23/22Z RAP INITIALIZED THIS ACTIVITY RATHER WELL AND ACTUALLY  
SHOWS A SLIGHT AREAL EXPANSION OVER THE NEXT SEVERAL HOURS AS THE  
REGION OF ISENTROPIC LIFT PROPAGATES NORTHEAST INTO PARTS OF  
SOUTHEAST GEORGIA AND EVENTUALLY SOUTH COASTAL SOUTH CAROLINA  
THROUGH 24/06Z. WILL LIKELY KEEP POPS IN THE ISOLATED CATEGORY  
FOR NOW, BUT SOME AREAS COULD DEFINITELY SEE A FEW HUNDREDTHS  
OF AN INCH OVER THE NEXT FEW HOURS, INCLUDING THE SAVANNAH METRO  
AREA. ONCE THIS REGION OF LIFT EXITS OFF THE MIDDLE SOUTH  
CAROLINA COAST AFTER 1-2 AM, EXPECT A MOSTLY DRY NIGHT.  
 
TEMPERATURES: A LARGE THERMAL GRADIENT IS IN PLACE THIS EVENING  
WITH THE WEDGE FRONT BISECTING THE REGION. NIGHTTIME LOWS (6PM-  
7AM) WILL LIKELY OCCUR THIS EVENING FOR MANY LOCATIONS WITH  
TEMPERATURES EXPECTED TO SLOWLY RISE OVERNIGHT AS THE WEDGE  
FRONT IS EVENTUALLY OVERTAKEN FROM THE SOUTH BY THE SYNOPTIC  
WARM FRONT. BY DAYBREAK, TEMPERATURES ARE EXPECTED TO BE IN THE  
MID-UPPER 60S WITH BREEZY CONDITIONS. ADJUSTED NIGHTTIME LOWS  
SLIGHTLY BASED ON CURRENT OBSERVATIONS AND SHORT TERM TRENDS.  
UPDATED TEMPERATURES SHOW LOWS FROM THE LOWER 50S ACROSS FAR  
INTERIOR SOUTHEAST SOUTH CAROLINA TO THE MID 60S ALONG THE  
ALTAMAHA.  
 
FOG: COASTAL WEBCAMS, PILOT BOAT REPORTS AND A FEW SHIP  
OBSERVATIONS SHOW WIDESPREAD DENSE FOG HAS DEVELOPED ACROSS THE  
NEARSHORE WATERS OF SOUTHEAST SOUTH CAROLINA AND FAR SOUTHERN  
SOUTH CAROLINA. THIS FOG IS EXPECTED TO MOVE STEADILY  
INLAND AND NORTH THROUGH THE EVENING HOURS, IMPACTING COASTAL  
GEORGIA INTO THE BEAUFORT-HILTON HEAD AREAS EARLY, THEN  
SPREADING WELL INLAND AND INTO THE CHARLESTON METRO AREA  
OVERNIGHT. DENSE FOG IS LIKELY TO OCCUR WITH NARRE-TL  
PROBABILITIES FOR DENSE FOG RUNNING WELL ABOVE 80% IN MANY  
AREAS. DENSE FOG ADVISORIES ARE LIKELY TO BE ISSUED. THE FOG IS  
EXPECTED TO STEADILY LIFT FROM SOUTH-NORTH DURING THE EARLY  
MORNING HOURS SUNDAY AS THE WARM FRONT LIFTS NORTH AND LOW-LEVEL  
WINDS INCREASE. EXPECT THE DENSE FOG TO MOSTLY CLEAR SOUTHEAST  
GEORGIA BY 4-5AM AND THE CHARLESTON TRI-COUNTY AREA BY 6-7AM.  
 

 
   
SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY/
 
 
SUNDAY AND SUNDAY NIGHT: A FAST MOVING COLD FRONT WILL APPROACH THE  
ARE FROM THE WEST IN THE MORNING AND THEN PUSH OFFSHORE BY THE LATE  
AFTERNOON. GOOD FRONTAL FORCING WILL RESULT IN A BAND OF SHOWERS  
THAT SHOULD MAINTAIN ACROSS THE FORECAST AREA. THE BEST RAIN CHANCES  
WILL BE DURING THE LATE MORNING TO EARLY AFTERNOON WITH ABRUPT  
DRYING TAKING PLACE BEHIND THE FRONT. THERE ARE SOME INDICATIONS OF  
VERY WEAK INSTABILITY ALONG AND AHEAD OF THE FRONT, BUT NOT ENOUGH  
TO INTRODUCE THUNDER TO THE FORECAST. TEMPERATURES WILL WARM QUICKLY  
IN THE MORNING WITH UPPER 70S AND EVEN SOME LOW 80S POSSIBLE  
DEPENDING ON HOW INSOLATION WORKS OUT. SOUTHWESTERLY WINDS WILL  
BECOME GUSTY IN THE MORNING IN THE WARM MIXING AHEAD OF THE FRONT,  
WITH GUSTS INTO THE 25-30 MPH RANGE EXPECTED. THEN BEHIND THE FRONT  
WINDS WILL TURN WESTERLY AND REMAIN GUSTY AS COOLER AIR STARTS TO  
FILTER IN. THROUGH THE OVERNIGHT, SKIES WILL CLEAR BEHIND THE FRONT  
AND WINDS WILL GRADUALLY RELAX. LOWS ARE FORECAST TO RANGE FROM  
AROUND 40 INLAND TO THE MID AND UPPER 40S ALONG THE COAST.  
 
LAKE WINDS: WIND. AROUND LAKE MOULTRIE WILL BECOME GUSTY ON SUNDAY  
OUT OF THE SOUTHWEST. GUSTS TO 25 KNOTS WILL BE POSSIBLE ON THE  
LAKESHORE, ESPECIALLY ON THE SOUTH AND WESTERN SIDES OF THE LAKE.  
THEN BEHIND A COLD FRONT IN THE AFTERNOON WINDS WILL TURN MORE  
WESTERLY AND NORTHWESTERLY THROUGH THE OVERNIGHT. GUSTS TO 25 KNOTS  
WILL STILL BE POSSIBLE AND A LAKE WIND ADVISORY COULD BE NEEDED.  
 
MONDAY THROUGH TUESDAY: HIGH PRESSURE WILL PREVAIL THROUGH THE EARLY  
PART OF THE WEEK WITH QUIET CONDITIONS. HIGHS ON MONDAY ARE FORECAST  
TO RANGE FROM THE MID TO UPPER 60S, THEN INTO THE UPPER 60S AND LOW  
70S ON TUESDAY. MONDAY NIGHT WILL BRING GOOD RADIATIONAL COOLING  
CONDITIONS AND LOWS WILL FALL INTO THE UPPER 30S INLAND, AND MID TO  
UPPER 40S ALONG THE COAST.  
 

 
   
LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/
 
 
ZONAL FLOW IN THE MID AND UPPER LEVELS WILL PREVAIL UNTIL LATE IN  
THE WEEK, WHEN A SHORT WAVE TROUGH IS CURRENTLY FORECAST TO  
APPROACH THE REGION. AT THE SURFACE THERE REMAIN MODEL DIFFERENCES,  
AND AS SUCH OUR CONFIDENCE WEDNESDAY THROUGH FRIDAY IS LOW. DUE THE  
UNCERTAINTY WE HAVE LEANED CONSIDERABLY TOWARD THE PREVIOUS FORECAST  
WHICH SHOWS NO MORE THAN CHANCE POP'S THROUGH THE PERIOD, WHILE  
TEMPS WILL AVERAGE ABOVE NORMAL AS THE CALENDAR CHANGES FROM  
FEBRUARY TO MARCH.  
 

 
   
AVIATION /00Z SUNDAY THROUGH THURSDAY/
 
 
WIDESPREAD FOG/STRATUS IS EXPECTED TO IMPACT BOTH KCHS AND KSAV  
OVERNIGHT. THE FOG COULD REACH KSAV VERY EARLY, THEN SPREAD INTO  
THE KCHS TERMINAL IN THE 03-06Z TIMEFRAME. VSBYS/CIGS BELOW  
AIRFIELD MINIMUMS ARE LIKELY, ESPECIALLY AT KSAV WHERE  
WIDESPREAD DENSE FOG IS LIKELY. CONDITIONS WILL IMPROVE FROM  
SOUTH-NORTH EARLY SUNDAY AS A WARM FRONT LIFTS NORTH, CLEARING  
KSAV BY 09-10Z AND KCHS 11-13Z. A PERIOD OF VFR WILL OCCUR JUST  
BEFORE A COLD FRONT PUSHES THROUGH THE TERMINAL AROUND 17Z. THE  
FRONT WILL BE ACCOMPANIED BY AN AREA OF RAIN. INTRODUCED 5SM IN  
-RA FOR NOW. WEST/NORTHWEST WINDS WILL PREVAIL AFTER FROPA.  
GUSTY WINDS WILL IMPACT THE TERMINAL FROM 12-13Z ON.  
 
EXTENDED AVIATION OUTLOOK: THE NEXT CHANCE OF ANY SUB-VFR WEATHER  
WILL NOT BE UNTIL THE MIDDLE OF NEXT WEEK. ALSO, GUSTY SW AND W  
WINDS WILL OCCUR AT TIMES SUNDAY, PEAKING AROUND 20-25 KT AT  
BOTH TERMINALS.  
 

 
   
MARINE
 
 
TONIGHT: ISSUED A MARINE DENSE FOG ADVISORY FOR THE GEORGIA AND  
BEAUFORT NEARSHORE LEGS THROUGH NOON SUNDAY. WIDESPREAD DENSE  
SEA FOG HAS DEVELOPED AND WILL MOVE SLOWLY NORTH THROUGH THE  
NIGHT, LIKELY IMPACTING CHARLESTON HARBOR AND THE CHARLESTON  
NEARSHORE WATERS. THE ADVISORY MAY NEED TO BE EXPANDED LATER  
THIS EVENING. OTHERWISE, WINDS WILL TURN SOUTHERLY THROUGH THE  
NIGHT WITH SPEEDS GENERALLY HOLDING LESS THAN 10 KT. SEAS WILL  
AVERAGE 2-4 FT.  
 
SUNDAY THROUGH THURSDAY: SOUTHWESTERLY WINDS WILL STRENGTHEN AND  
SHOULD HELP TO DISPERSE LINGERING MORNING SEA FOG BY THE LATE  
MORNING HOURS. WINDS WILL BECOME STRONG ENOUGH THAT SMALL CRAFT  
ADVISORIES WILL LIKELY BE NEEDED, ESPECIALLY FOR CHARLESTON HARBOR,  
THE CHARLESTON COUNTY WATERS, AND THE OUTER GEORGIA WATERS. THEN  
OVERNIGHT BEHIND THE FRONT, WINDS WILL BECOME NORTHWESTERLY AND  
REMAIN ELEVATED CLOSE TO ADVISORY LEVELS. CONDITIONS WILL THEN  
BECOME MUCH CALMER STARTING MONDAY AS HIGH PRESSURE BUILDS IN, WELL  
BELOW ADVISORY THRESHOLDS THROUGH THE LATTER PART OF THE WEEK.  
 

 
   
CLIMATE
 
 
RECORD HIGHS FOR FEBRUARY 24...  
KCHS: 81/2017 AND PREVIOUS  
KCXM: 81/1930 KSAV: 86/2012  
 
RECORD HIGH MINS FOR FEBRUARY 24...  
KCHS: 60/1992 AND PREVIOUS  
KCXM: 63/2018  
KSAV: 64/1980  
 

 
   
CHS WATCHES/WARNINGS/ADVISORIES
 
 
GA...NONE.  
SC...NONE.  
MARINE...DENSE FOG ADVISORY UNTIL NOON EST SUNDAY FOR AMZ352-354.  
 

 
 

 
 
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