Area Forecast Discussion
Issued by NWS Charleston, SC

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000 FXUS62 KCHS 210834 AFDCHS AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHARLESTON SC 434 AM EDT MON APR 21 2014 .SYNOPSIS...
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HIGH PRESSURE WILL BUILD OVER THE REGION THROUGH TONIGHT. A WEAKENING COLD FRONT WILL MOVE ACROSS THE AREA EARLY TUESDAY NIGHT. HIGH PRESSURE WILL THEN PREVAIL INTO THE WEEKEND.
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&& .NEAR TERM /THROUGH TONIGHT/...
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PRE-DAWN...LINGERING CLOUDS DECREASING IN COVERAGE ALONG AND E OF I-95 CORRIDOR IN SOUTH CAROLINA WHILE SKIES CLEARED MUCH EARLIER ACROSS MUCH OF SE GEORGIA. INLAND GEORGIA AREAS NORTH TO AROUND HAMPTON AND ALLENDALE SOUTH CAROLINA HAVE SEEN STRONG RADIATIONAL COOLING WITH LIGHT SURFACE WINDS. THIS HAS ALLOWED A FEW READINGS TO DIP INTO THE UPPER 40S..ELSEWHERE TEMPS IN THE 50S EARLY THIS MORNING. MODELS CONTINUE TO THIN THE RIBBON OF MOISTURE BELOW THE SUBSIDENCE INVERSION ABOVE 850 MB WITH TIME...A FEW AREAS OF STRATOCU WILL PROBABLY STILL BE LINGERING NEAR DAYBREAK BUT THE CLEARING TREND LOOKS ON TRACK. AN UPPER TROUGH AND SERIES OF SHORT WAVES OVER THE PLAINS STATES WAS STEADILY SHIFTING A SHORT WAVE RIDGE EASTWARD TOWARD GEORGIA AND THE CAROLINAS THIS MORNING. THIS PATTERN WILL CONTINUE TO BOOT THE LOW PRES OFF THE CAROLINA COAST FURTHER OFFSHORE INTO THE WESTERN ATLC. THE ARRIVAL OF THE UPPER RIDGE AND DEEP LAYERED DRY AIR WILL SPELL SUNSHINE AND MILDER TEMPS FOR THE FORECAST AREA. ALONG THE EASTERN HALF OF THE FORECAST AREA...WE SHOULD BE ABLE TO SHAKE MOST OF THE LINGERING STRATOCU BY MID MORNING AT THE LATEST PER NAM AND LOCAL WRF FORECAST SOUNDINGS. LOW LEVEL THICKNESS PROGS AND 00Z GUIDANCE SUGGEST OUR FORECAST TEMP PROFILES INCLUDING HIGHS MID/UPPER 70S ARE ON TRACK. COASTAL AREAS WILL NOTICE A DEFINITE DECREASE IN WIND SPEEDS THIS AFTERNOON AS THE GRADIENT GOES FLAT WITH A WEAK SEA BREEZE LIKELY ALONG BEACHES AND BARRIER ISLANDS LATER THIS AFTERNOON. TONIGHT...MOSTLY CLEAR SKIES WITH A FEW HIGH CLOUDS. RADIATIONAL COOLING POTENTIAL LOOKS GOOD INLAND WITH RURAL AREAS POSSIBLY DIPPING INTO THE UPPER 40S WITH LOWER TO MID 50S LOW TEMPS ANTICIPATED ALONG COASTAL AREAS.
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&& .SHORT TERM /TUESDAY THROUGH THURSDAY/...
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TUESDAY...A MID AND UPPER LEVEL SHORTWAVE TROUGH WILL MOVE ACROSS THE AREA TUESDAY AFTERNOON...FOLLOWED BY THE PASSAGE OF A WEAK COLD FRONT FROM THE NORTHWEST BY EARLY TUESDAY NIGHT. FORCING ASSOCIATED WITH THESE FEATURES SHOULD RESULT IN A SLIGHT CHANCE TO CHANCE OF SHOWERS THROUGHOUT THE AREA TUESDAY AFTERNOON INTO EARLY TUESDAY NIGHT...WITH GREATEST CHANCES EXPECTED TUESDAY EVENING INTO EARLY TUESDAY NIGHT AS THE COLD FRONT SHIFTS OVER THE AREA. PRECIP WILL LIKELY END WITH FROPA EARLY TUESDAY NIGHT. SBCAPES BETWEEN 500-1000 J/KG AND LIFTED INDEX VALUES BETWEEN -2 TO -4 C COULD SUPPORT A FEW THUNDERSTORMS AHEAD OR ALONG THE FRONT...BUT THE SEVERE WEATHER THREAT WILL REMAIN QUITE LOW GIVEN WEAK DOWNSLOPING WIND FIELDS OVER THE REGION. THE DOWNSLOPING WIND COMPONENT ALONG WITH COMPRESSIONAL HEATING AHEAD OF THE FRONT SHOULD RESULT IN AFTERNOON TEMPS IN THE LOWER 80S AWAY FROM THE COAST. OVERNIGHT TEMPS WILL COOL OFF QUICKLY POST FROPA...REACHING THE MID 50S INLAND TO LOW 60S ALONG THE COAST. WEDNESDAY AND THURSDAY...HIGH PRESSURE WILL BUILD FROM THE NORTH/NORTHWEST BEHIND A COLD FRONT SHIFTING WELL INTO THE WESTERN ATLANTIC ON WEDNESDAY...BEFORE GRADUALLY SLIDING OFF THE MID ATLANTIC COAST ON THURSDAY. THE PATTERN WILL RESULT IN QUIET/DRY CONDITIONS INTO MIDWEEK...WITH SLIGHTLY COOLER TEMPS ON WEDNESDAY MODIFYING ON THURSDAY AS A NORTHERLY FLOW BECOMES SOUTHERLY IN RESPONSE TO THE POSITION OF THE HIGH PRESSURE CENTER SHIFTING OFFSHORE. IN GENERAL...OVERALL HIGH TEMPS WILL RANGE IN THE MID/UPPER 70S ON WEDNESDAY...WITH A FEW 80S IN SOUTHEAST GEORGIA AWAY FROM THE COAST. BY THURSDAY...THE SOUTHERLY FLOW WILL FAVOR AFTERNOON HIGH TEMPS IN THE LOW 80S FOR MOST LOCATIONS AWAY FROM THE COAST.
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&& .LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/...
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THE AREA WILL REMAIN ALONG THE WESTERN EDGE OF HIGH PRESSURE CENTERED OVER THE WESTERN ATLANTIC INTO THE WEEKEND. SOUTHERLY FLOW OVER THE AREA SHOULD FAVOR PERIODS OF SHOWERS AND/OR THUNDERSTORMS EACH AFTERNOON AS SFC TEMPS PEAK INTO THE LOW TO MID 80S AWAY FROM THE COAST...ESPECIALLY WITH ENHANCED TROUGHING FROM THE NORTH SATURDAY. THERE ARE SOME INDICATIONS OF ANOTHER COLD FRONT APPROACHING THE SOUTHEAST EARLY NEXT WEEK...BUT CONFIDENCE REMAINS LOW IN THE TIMING AND POSITION OF THE FRONT INTO EARLY NEXT WEEK. AT THIS TIME...HAVE MAINTAINED OVERALL HIGH TEMPS IN THE LOWER 80S SUNDAY AND MONDAY...WITH A SLIGHT CHANCE OR SHOWERS AND/OR THUNDERSTORMS MONDAY AS MOISTURE DEEPENS OVER THE SOUTHEAST.
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&& .AVIATION /08Z MONDAY THROUGH FRIDAY/...
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VFR CONDITIONS TODAY AND TONIGHT WITH OCCASIONAL WIND GUSTS 15-18 KT FROM THE N POSSIBLE DURING THE MID TO LATE MORNING HOURS. EXTENDED AVIATION OUTLOOK...VFR CONDITIONS EXPECTED TUESDAY. THERE IS A SMALL CHANCE OF SOME IFR/MVFR CONDITIONS WITH THUNDERSTORMS TUESDAY EVENING INTO EARLY TUESDAY NIGHT. VFR CIGS/VSBYS WILL THEN PREVAIL WEDNESDAY THROUGH LATE WEEK.
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&& .MARINE...
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WE WERE ABLE TO LOWER THE SMALL CRAFT ADVISORY IN THE CHARLESTON HARBOR EARLIER AND EXPECT NEAR SHORE WATERS SOUTH OF CHARLESTON COUNTY TO COME DOWN PRIOR TO DAYBREAK GIVEN LATEST WIND/SEA TRENDS. WE MAINTAINED THE ADVISORY FOR CHARLESTON COUNTY NEAR SHORE WATERS UNTIL LATER THIS MORNING GIVEN THE PROXIMITY TO A TIGHTER OFFSHORE GRADIENT ALLOWING SEA HEIGHTS TO DIMINISH SLOWER ALONG THE CENTRAL SOUTH CAROLINA COAST. AT 2 AM...SEAS AT BUOY 41004 WERE DOWN TO 9 FT AND SLOWLY FALLING. OTHERWISE...WINDS AND SEAS WILL DIMINISH THROUGH TONIGHT AS HIGH PRESSURE BUILDS FROM THE WEST. BY LATER TONIGHT...A LIGHT OFFSHORE FLOW SHOULD DAMPEN NEAR SHORE SEAS TO LESS THAN 3 FT WITH SEAS OVER THE GEORGIA WATERS CLOSER TO THE GULF COAST FALLING BELOW ADVISORY CRITERIA BY THIS EVENING WITH 3 TO 5 FT SEAS OVERNIGHT. TUESDAY THROUGH SATURDAY...WINDS/SEAS WILL LIKELY REMAIN BELOW SMALL CRAFT ADVISORY THRESHOLDS THROUGH EARLY THIS WEEKEND. IN GENERAL...A SOUTHWEST FLOW WILL STRENGTHEN TUESDAY AND TUESDAY EVENING AHEAD OF AN APPROACHING COLD FRONT...WITH SPEEDS PEAKING AROUND 15 KT. SEAS WILL PEAK BETWEEN 2-4 FT...HIGHEST IN OFFSHORE GEORGIA WATERS. THE FRONT WILL THEN MOVE OFFSHORE TUESDAY NIGHT...LEADING TO IMPROVING CONDITIONS AS HIGH PRESSURE BUILDS FROM THE NORTH/NORTHWEST AND DOMINATES THE WATERS THROUGH LATE WEEK.
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&& .CHS WATCHES/WARNINGS/ADVISORIES...
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GA...NONE. SC...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT EARLY THIS MORNING FOR AMZ352-354. SMALL CRAFT ADVISORY UNTIL MIDNIGHT EDT TONIGHT FOR AMZ374. SMALL CRAFT ADVISORY UNTIL 11 AM EDT THIS MORNING FOR AMZ350.
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&& $$ SYNOPSIS... NEAR TERM... SHORT TERM...DPB LONG TERM...DPB AVIATION... MARINE...DPB

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