005  
FXUS62 KCHS 241519  
AFDCHS  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE CHARLESTON SC  
1019 AM EST MON FEB 24 2020  
   
SYNOPSIS
 
 
A DEVELOPING WARM FRONT WILL LIFT NORTH OF THE REGION TONIGHT,  
FOLLOWED BY A PAIR OF COLD FRONTS DURING THE MIDDLE OF THE  
WEEK. HIGH PRESSURE RETURNS THURSDAY AND FRIDAY, WITH A WEAK  
COLD FRONT EXPECTED SATURDAY.  
 

 
   
NEAR TERM /THROUGH TONIGHT/
 
 
AS OF 1015 AM: KCLX INDICATED SEVERAL PATCHES OF 10-20 DBZ  
RETURNS ACROSS THE FORECAST AREA. THESE LIGHT RETURNS WERE  
LIKELY ASSOCIATED SCATTERED AREAS OF SPRINKLES. I WILL UPDATE  
THE FORECAST TO ADD A MENTION OF SPRINKLES AND INCREASED CLOUD  
COVER TO THE FORECAST LATE THIS MORNING. FOR THIS AFTERNOON,  
LIGHT SHOWERS WILL INCREASE IN COVERAGE FROM THE WEST. THE  
SHOWERS MAY PRODUCE AROUND A TENTH OF AN INCH OF RAINFALL BY  
LATE THIS AFTERNOON.  
 
PREVIOUS DISCUSSION:  
TODAY: MID LEVEL FLOW WILL SLOWLY BACK TODAY, WELL AHEAD OF A  
STORM SYSTEM EJECTING OUT OF CENTRAL PLAINS. A WARM FRONT IS  
FORECAST TO TAKE SHAPE LATER THIS MORNING ACROSS SOUTH GA AND  
GRADUALLY LIFT TOWARD THE SAVANNAH RIVER LATE IN THE DAY. MODELS  
INDICATE FAIRLY DEEP MOISTURE IN THE 850 MB TO 500 MB LAYERS  
WILL SPREAD WEST TO EAST TO THE NORTH OF I-16 TODAY AND CHANCES  
FOR LIGHTER RAINS WILL GENERALLY INCREASE FROM SOUTH TO NORTH  
AND FROM EAST TO WEST LATER TODAY. WE HAVE POPS RANGING FROM  
20/30 TO THE SOUTH OF I-16 TO LIKELY RIGHT ALONG OUR FAR NW  
CORRIDOR WITH LESSER CHANCES FOR SOME LIGHT MEASURABLE RAINS  
ALONG COASTAL SC PRIOR TO SUNSET. CLOUDS AND ANY PRECIP WILL  
TEMPER HOW WARM IT COULD GET TODAY IF OUR REGION WERE TO SEE  
MORE IN THE WAY OF SUNSHINE (WHICH IS UNLIKELY). WE MAINTAINED  
HIGHS IN THE MID 60S NORTH TO THE WARMEST READINGS POSSIBLY IN  
THE LOWER 70S INLAND AND SOUTH OF SAVANNAH.  
 
TONIGHT: THE WARM AIR ADVECTION PATTERN WILL CONTINUE TO  
STRENGTHEN AS THE WARM FRONT LIFTS NORTH OF THE REGION AFTER  
MIDNIGHT. MODELS REMAIN CONSISTENT ON STRONG MOISTURE TRANSPORT  
AND BUILDING UPPER DIFLUENCE AS RAINS INCREASE IN COVERAGE AND  
INTENSITY. STEERING FLOW LOOKS PROGRESSIVE ENOUGH TO KEEP MOST  
OF THE CONVECTIVE ELEMENTS PROGRESSIVE OVERNIGHT AND WE KEPT  
QPF AMOUNTS MOSTLY 1/2 INCH OR SO, ALTHOUGH HEAVIER BANDS OF  
SHOWERS COULD STILL RESULT IN SOME 1 INCH BANDS INLAND FROM  
I-95. SOUTHWEST WINDS WILL INCREASE ALONG COASTAL ZONES  
OVERNIGHT AS TEMPS WARM FROM THE MID TO UPPER 50S DURING THE  
EVENING HOURS TO THE LOWER TO MID 60S MANY AREAS AFTER  
MIDNIGHT.  
 

 
   
SHORT TERM /TUESDAY THROUGH THURSDAY/
 
 
TUESDAY: AN AMPLIFYING AND LARGE SCALE MID AND UPPER TROUGH WILL  
COVER MUCH OF THE CENTRAL AND EASTERN CONUS, AS A STRONG RIDGE ALOFT  
EXISTS OVER THE CARIBBEAN. AT THE SURFACE, AN OCCLUDED LOW WILL LIFT  
SLOWLY INTO THE OHIO VALLEY, WITH A TRAILING COLD FRONT TO SLOWLY  
APPROACH THE LOCAL AREA. BUT THE FRONT STALLS OUT AS IT BECOMES MORE  
PARALLEL WITH THE FLOW ALOFT. WIDESPREAD CONVECTIVE RAINS WILL BE  
ONGOING AT DAYBREAK IN ASSOCIATION WITH A POTENT SOUTHERN STREAM  
UPPER LEVEL JET. BUT FORCING DIMINISHES DURING THE AFTERNOON, SO  
RAIN CHANCES DROP FROM 90-100% IN THE MORNING DOWN TO 50-70% IN THE  
AFTERNOON. POOR LAPSE RATES AND CONSIDERABLE CLOUD COVER WILL BE  
PRESENT, BUT A SWATH OF MLCAPE AS GREAT AS 300-500 J/KG IS FORECAST  
TO DEVELOP AHEAD OF THE COLD FRONT DURING THE AFTERNOON. THIS MAY BE  
ENOUGH FOR ISOLATED T-STORMS, MAINLY NEAR AND WEST OF I-95. DESPITE  
THE EXTENSIVE CLOUD COVER, WARM ADVECTION WILL PREVAIL, AS 850 MB  
TEMPS REACH 11-13C. THIS WILL ALLOW FOR MAX TEMPS TO CLIMB TO 70F OR  
GREATER INLAND FROM US-17. THE RISK OF T-STORMS ENDS BY SUNSET, BUT  
SCATTERED TO WIDESPREAD SHOWERS WILL CONTINUE THROUGH THE NIGHT  
WITHIN A DEEP FEED OF SUB-TROPICAL MOISTURE AND FORCING FROM THE  
UPPER JET AND VARIOUS MID LEVEL IMPULSES. TEMPS WILL BE ABOUT 15-20F  
ABOVE CLIMO. ADDITIONAL QPF FOR TUESDAY AND TUESDAY NIGHT WILL  
AVERAGE 1/4 TO 1/3 INCHES. THESE RAINS, PLUS THOSE OF TODAY AND  
TONIGHT, WILL MAINTAIN THE FLOODING OF ALL MAJOR RIVERS IN OUR  
FORECAST AREA.  
 
WEDNESDAY: A DEEP TROUGH ALOFT WILL SWEEP EAST TOWARD THE  
APPALACHIANS, SENDING A SECONDARY COLD FRONT THROUGH THE LOCAL AREA  
LATE DAY OR EARLY AT NIGHT. THE MAIN DEEP LAYERED MOISTURE AXIS WILL  
SHIFT OFFSHORE AS THIS OCCURS, ALLOWING FOR DECREASING RAIN CHANCES  
THROUGHOUT THE DAY. THERE ISN'T ANY COLD ADVECTION UNTIL WEDNESDAY  
NIGHT, SO MAX TEMPS WILL AGAIN BE WELL ABOVE NORMAL, BEFORE DROPPING  
SOME 30F BY THURSDAY MORNING AS THE SYNOPTIC FLOW VEERS TO THE WEST-  
NORTHWEST. THIS INFLUX OF COLDER AIR, PLUS STEADY AND LARGE  
ISALLOBARIC PRESSURE RISES COULD PRODUCE A LAKE WIND ADVISORY ACROSS  
LAKE MOULTRIE WEDNESDAY NIGHT INTO THURSDAY.  
 
THURSDAY: AN ENORMOUS MID AND UPPER TROUGH COVERS A LARGE PART OF  
THE CONUS, INCLUDING THE LOCAL VICINITY, AS COLDER HIGH PRESSURE AT  
THE SURFACE BUILDS IN FROM THE WEST. THE 850 MB 0C ISOTHERM  
PENETRATES FAR OFFSHORE AND EVEN INTO NORTHERN FLORIDA, LEAVING US  
WITH A MUCH COLDER DAY, DESPITE PLENTY OF INSOLATION.  
 

 
   
LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/
 
 
COLDER WEATHER WILL PREVAIL FOR THE END OF FEBRUARY AND START OF  
MARCH, AS A BROAD AND DEEP TROUGH PERSISTS OVER THE AREA. FOR THE  
MOST PART HIGH PRESSURE WILL DOMINATE AT THE SURFACE AND IN THE  
LOWER LEVELS. WITHIN A DEEP OFFSHORE FLOW, MOISTURE WILL BE  
SIGNIFICANTLY LIMITED, SO THERE IS LITTLE IF ANY CHANCE OF PRECIP  
DURING THIS TIME. THE EXCEPTION MIGHT BE SATURDAY WHEN A DECENT  
SHORT WAVE MOVES THROUGH, AND COULD RESULT IN A FEW SHOWERS. FOR NOW  
WE HAVE CAPPED POP AT LESS THAN 15%, SO NO MENTION IN THE FORECAST.  
ALSO, CONDITIONS FAR INLAND COULD FAVOR A POTENTIAL FOR ONE OR TWO  
LATE NIGHT/EARLY MORNING FREEZES.  
 

 
   
AVIATION /15Z MONDAY THROUGH FRIDAY/
 
 
VFR CONDITIONS ANTICIPATED TODAY WITH THE BULK OF THE CLOUD-LAYER  
MOISTURE ABOVE 3 KFT. TONIGHT, A WARM FRONT WILL MOVE THROUGH  
AND EVENTUALLY NORTH OF THE TERMINALS. INCREASING CHANCES FOR  
LOWER CIGS BY LATE EVENING WITH RAIN CHANCES ALSO WILL BE ON THE  
RISE FOR THE OVERNIGHT. SURFACE WINDS WILL GENERALLY BE LIGHT  
TODAY, THEN INCREASE FROM SOUTHERLY DIRECTIONS LATE TONIGHT AS  
TEMPS RISE ALONG THE COASTAL CORRIDOR.  
 
EXTENDED AVIATION OUTLOOK: A PAIR OF COLD FRONTS WILL BRING FLIGHT  
RESTRICTIONS TUESDAY THROUGH EARLY WEDNESDAY. VFR WITH BREEZY  
CONDITIONS ARE EXPECTED BEHIND THE SECOND COLD FRONT INTO  
THURSDAY.  
 

 
   
MARINE
 
 
TODAY: RELATIVELY TRANQUIL CONDITIONS MUCH OF TODAY AS THE PRESSURE  
PATTERN REMAINS WEAK AHEAD OF A DEVELOPING WARM FRONT ACROSS SOUTH  
GA. THERE WILL BE LINGERING 2-3 FT SWELLS OFFSHORE BUT WINDS WILL  
REMAIN VERY LIGHT EARLY ON AND LESS THAN 15 KT PRIOR TO DUSK.  
AS THE WARM FRONT LIFTS NORTH TONIGHT, SOUTH FLOW WILL INCREASE  
AND SEAS WILL GRADUALLY BUILD AFTER MIDNIGHT. THERE IS POTENTIAL  
FOR BOTH GUSTS TO 25 KT AND 6 FT SEAS DEVELOPING ACROSS OUTER  
GA WATERS CLOSER TO THE GULF STREAM BUT GIVEN TRICKY MIXING  
PROFILES, WE OPTED TO WAIT ON THE SCA ISSUANCE, STILL LIKELY TO  
BE ISSUED LATER TODAY FOR AMZ374.  
 
TUESDAY THROUGH SATURDAY: CHANGEABLE CONDITIONS ACROSS THE MARITIME  
COMMUNITY DURING THE MID AND LATE WEEK PERIOD. HIGH PRESSURE TO THE  
EAST AND SOUTHEAST ON TUESDAY WILL GIVE WAY TO A PAIR OF COLD FRONTS  
THAT MOVE THROUGH LATE WEDNESDAY OR WEDNESDAY NIGHT. THIS IS  
FOLLOWED BY HIGH PRESSURE BUILDING FROM THE WEST ON THURSDAY AND  
FRIDAY. CONDITIONS IN ADVANCE OF THE COLD FRONT FAVOR SMALL CRAFT  
ADVISORIES OVER AT LEAST AMZ350 AND AMZ374. BEHIND THE FRONTS THERE  
WILL BE THE NEED FOR ADDITIONAL ADVISORIES AT TIMES OVER ALL WATERS,  
INCLUDING CHARLESTON HARBOR. THERE IS EVEN A LOW END CHANCE FOR  
MARGINAL GALES WEDNESDAY NIGHT INTO EARLY THURSDAY OVER THE OUTER  
GEORGIA WATERS, WHERE THE GREATEST MIXING OF THE COLD AIR WILL  
OCCUR.  
 
BOTH THE NAM AND SREF DEPICT SOME POTENTIAL FOR SEA FOG TUESDAY  
NIGHT INTO WEDNESDAY, BUT CONDITIONS DON'T APPEAR FAVORABLE FOR SUCH  
AN OCCURRENCE. IF ANY REDUCTION IN VISIBILITY WERE TO OCCUR IT WOULD  
BE DUE TO LOW STRATUS. SO WE HAVE NO MENTION IN THE GRIDS OR COASTAL  
WATERS FORECAST.  
 

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

 
 

 
NEAR TERM...NED  
SHORT TERM...33  
LONG TERM...33  
AVIATION...  
MARINE...  
 
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