Area Forecast Discussion
Issued by NWS Charleston, SC

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000 FXUS62 KCHS 230445 AFDCHS AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHARLESTON SC 1245 AM EDT WED APR 23 2014 .SYNOPSIS...
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A COLD FRONT WILL CROSS THE AREA LATER THIS MORNING. HIGH PRESSURE WILL BUILD INTO THE REGION ON WEDNESDAY AND THEN PREVAIL THROUGH THE END OF THE WEEK. A COLD FRONT MAY DRIFT IN FROM THE NORTH THIS WEEKEND BEFORE WARMER CONDITIONS RETURN EARLY NEXT WEEK AHEAD OF A STRONGER COLD FRONT TO THE WEST.
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&& .NEAR TERM /UNTIL 6 AM THIS MORNING/...
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SHORTWAVE ENERGY HAS PUSHED OFF THE COAST AND ATTENDANT DNVA/SUBSIDENCE WILL LIKELY PRECLUDE ANY REDEVELOPMENT OF SHOWER ACTIVITY AHEAD OF AN APPROACHING COLD FRONT. SKIES WILL GRADUALLY CLEAR OVER THE NEXT FEW HOURS WITH SOME LOW STRATUS LIKELY TO REFORM AS THE HIGHER CLOUD CANOPIES PUSH OFFSHORE. A LIGHTER WIND FIELD COUPLED WITH WET GROUND AND CLEARING SKIES WILL SUPPORT AREAS OF FOG ACROSS INTERIOR PORTIONS OF SOUTHEAST GEORGIA THROUGH SUNRISE. IT IS UNCLEAR WHETHER WIDESPREAD DENSE FOG WILL DEVELOP...BUT SOME FOG IS LIKELY. WILL BE WATCHING THIS AREA CAREFULLY FOR A POSSIBLE DENSE FOG ADVISORY. OTHERWISE...NUDGED LOWS THIS MORNING UP A DEGREE OR SO BASED ON CURRENT TRENDS.
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&& .SHORT TERM /6 AM THIS MORNING THROUGH FRIDAY/... WEDNESDAY AND WEDNESDAY NIGHT...WE WILL START THE DAY IN NORTHWEST FLOW ALOFT AHEAD OF THE DEEP RIDGE BUILDING IN FROM THE WEST. AT THE SURFACE...HIGH PRESSURE CENTERED OVER THE GREAT LAKES WILL BUILD IN ACROSS THE FORECAST AREA THROUGH THE OVERNIGHT. VERY DRY AIR IN THE MID/UPPER LEVELS COMBINED WITH THE LACK OF FORCING AND STRONG SUBSIDENCE INVERSION WILL KEEP THE FORECAST DRY. TEMPERATURES WILL BE COOLER THAN TUESDAY BEHIND THE FRONT...THOUGH THEY WILL STILL TOP OUT AROUND NORMAL. LOOK FOR HIGHS IN THE UPPER 70S TO AROUND 80. OVERNIGHT LOWS ARE EXPECTED TO FALL INTO THE LOW TO MID 50S IN MOST AREAS. THURSDAY THROUGH FRIDAY...THE INFLUENCE OF THE UPPER RIDGE WILL REACH ITS MAX INFLUENCE ON THURSDAY AS THE AXIS OF THE FEATURE MOVES ACROSS THE EASTERN CONUS. THEN BY FRIDAY...A MORE ZONAL FLOW WILL MOVE IN ALOFT IN RESPONSE TO A CLOSED LOW PROGRESSING INTO THE GREAT LAKES REGION. SURFACE HIGH PRESSURE WILL SLIDE EAST OF THE FORECAST AREA THURSDAY AFTERNOON AND WILL REMAIN OFFSHORE THROUGH FRIDAY. A FAST MOVING COLD FRONT WILL APPROACH FROM THE NORTH AND WEST FRIDAY AFTERNOON...AND MAY HELP TO SPARK A FEW SHOWERS AND THUNDERSTORMS. THURSDAY WILL BE DRY AS THE SUBSIDENCE INVERSION REMAINS IN PLACE PER MODEL SOUNDINGS. BUT BY FRIDAY...THE INVERSION WEAKENS ENOUGH TO ALLOW FOR 500-1000 J/KG WITHIN A BROAD CONVERGENCE ZONE BETWEEN THE APPROACHING COLD FRONT AND THE AFTERNOON SEA BREEZE. POPS HAVE BEEN KEPT IN THE SLIGHT CHANCE RANGE. TEMPERATURES FOR THURSDAY WILL BE ONCE AGAIN RIGHT AROUND NORMAL FOR LATE APRIL...HELD DOWN A BIT BY THE ONSHORE FLOW. FRIDAY WILL THEN SEE VALUES IN THE 80S THANKS TO THE SOUTHWEST FLOW ASSOCIATED WITH THE COLD FRONT. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... CONDITIONS SHOULD REMAIN FAIRLY DRY THIS WEEKEND ALONG THE WESTERN EDGE OF ATLANTIC HIGH PRESSURE AT THE SFC AND A ZONAL FLOW ALOFT. HOWEVER...A WEAK COLD FRONT COULD APPROACH FROM THE NORTH LATE SATURDAY INTO EARLY SUNDAY...LEADING TO THE POSSIBILITY OF A SHOWER AND/OR THUNDERSTORM. AT THIS TIME...THE FRONT LOOKS TO STALL NORTH OF THE AREA...THUS HAVE MAINTAINED A RAIN-FREE FORECAST. OVERALL HIGH TEMPS WILL BE WARMER THAN PREVIOUS DAYS...IN THE LOW/MID 80S EACH DAY. CHANCES OF PRECIP WILL THEN INCREASE MONDAY INTO TUESDAY AS SOUTHERLY FLOW PERSISTS BETWEEN ATLANTIC HIGH PRESSURE AND A LOW PRESSURE SYSTEM TRACKING EAST OVER THE CENTRAL UNITED STATES. A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS HAVE BEEN INCLUDED IN THE LATEST FORECAST AS INSTABILITY INCREASES WITH OVERALL HIGH TEMPS IN THE MID 80S AWAY FROM THE COAST. GREATEST CHANCES OF PRECIP SHOULD OCCUR ON TUESDAY AS A COLD FRONT ASSOCIATED WITH THE LOW PRESSURE SYSTEM APPROACHES THE SOUTHEAST DURING MIDWEEK. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
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KSAV...LOW STRATUS AND FOG ARE DEVELOPING ACROSS CENTRAL GEORGIA AS CLOUDS CLEAR. WINDS WILL BE A BIT LIGHTER OVER SOUTHEAST GEORGIA SO THERE IS A LIKELIHOOD THAT SOME FOG AND STRATUS WILL IMPACT THE KSAV TERMINAL WITH THE INITIAL TRAFFIC PUSH THIS MORNING. IT IS UNCLEAR ATTM HOW LOW CONDITIONS WILL GET WITH SHORT TERM GUIDANCE ESSENTIALLY USELESS AT THIS JUNCTURE. WILL CALL FOR PREVAILING MVFR VSBYS 08-12Z WITH TEMPO IFR VSBYS/CIGS FROM 10-12Z...HOWEVER IT IS VERY POSSIBLE THAT PREVAILING LIFR CONDITIONS WILL OCCUR. WILL AMEND AS NECESSARY. ONCE THE FOG AND STRATUS BURN OFF...EXPECT VFR CONDITIONS. KCHS...VFR FOR THE PERIOD. SOME LIGHT GROUND FOG COULD DEVELOP THROUGH SUNRISE...BUT WINDS SHOULD KEEP ANY IMPACTS LOW. EXTENDED AVIATION OUTLOOK...NO CONCERNS.
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&& .MARINE... LATE TUESDAY EVENING...OUTFLOW FROM SHOWERS/THUNDERSTORMS AND AN ASSOCIATED SURFACE TROUGH HAD DISRUPTED THE PRESSURE PATTERN ACROSS SOUTH CAROLINA NEARSHORE WATERS...AND THIS REGIME WILL CONTINUE TO PRESS SOUTH/EAST THROUGH GEORGIA WATERS. IN GENERAL...OFFSHORE WINDS 15 KT OR LESS WILL PREVAIL OVERNIGHT. A COLD FRONT WILL CROSS THE WATERS LATE TONIGHT/EARLY WEDNESDAY MORNING AND WINDS WILL VEER THROUGH THE NW TOWARD THE N. SEAS WILL REMAIN 2-3 FT ACROSS THE NEARSHORE WATERS AND 3-5 FT ACROSS THE OUTER GA WATERS. WEDNESDAY THROUGH SUNDAY...GENERALLY QUIET CONDITIONS ARE EXPECTED TO PREVAIL THROUGH THE WEEKEND WITH NO SMALL CRAFT ADVISORY CONDITIONS EXPECTED. HIGH PRESSURE WILL BUILD INTO THE AREA WEDNESDAY AND THEN SLIDE BY TO THE EAST THURSDAY. WEDNESDAY WILL START OFF WITH NORTHERLY FLOW WHICH WILL VEER AROUND TO MORE SOUTHERLY BY THURSDAY AFTERNOON. ANOTHER FAST MOVING COLD FRONT WILL MOVE THROUGH OVER THE WEEKEND WITH MORE HIGH PRESSURE BY SUNDAY. WINDS WILL BE 15 KT OR LESS...WITH SEAS 2-4 FT WEDNESDAY THEN 1-3 FT THEREAFTER. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...NONE. SC...NONE. MARINE...NONE. && $$ ST

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