Area Forecast Discussion
Issued by NWS Charleston, SC

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000 FXUS62 KCHS 070346 AFDCHS AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHARLESTON SC 1046 PM EST SAT FEB 6 2016 .SYNOPSIS... LOW PRESSURE WILL TRACK NORTH AND DEEPEN OFF THE SOUTHEAST COAST TONIGHT THROUGH SUNDAY....THEN WILL MOVE AWAY TOWARD THE NORTHEAST SUNDAY NIGHT. A COLD FRONT WILL CROSS THE AREA MONDAY. THEN...A DEEP TROUGH WILL REMAIN IN PLACE THROUGH THE MIDDLE OF NEXT WEEK...BRINGING UNSEASONABLY COOL CONDITIONS TO THE AREA. HIGH PRESSURE WILL BUILD OVER THE REGION LATE WEEK INTO NEXT WEEKEND. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... TONIGHT...A CLOSED MID AND UPPER LEVEL LOW OVER NORTHERN ALABAMA AS OF LATE-EVENING WILL SHIFT TOWARD THE FLORIDA PANHANDLE AND INTENSIFY TONIGHT AS ITS ASSOCIATED TROUGH TAKES ON A SLIGHT NEGATIVE TILT. AS THIS OCCURS...STRONG CYCLOGENESIS WILL TAKE PLACE OFF THE SOUTHEAST COAST AND SURFACE LOW PRESSURE WILL RAPIDLY INTENSIFY AS IT LIFTS NORTH-NORTHEAST FROM THE ATLANTIC COAST OF FLORIDA TO A POSITION OFF THE GEORGIA COAST BY DAYBREAK SUNDAY. THE TRACK AND INTENSITY OF THIS LOW...WHICH IS STILL SOMEWHAT UNCERTAIN...WILL HAVE BIG IMPLICATIONS ON THE FORECAST. DEEP MOISTURE AND STRONG FORCING FOR ASCENT DUE TO THE APPROACH OF THE UPPER LEVEL TROUGH HAS ALLOWED RAIN TO EXPAND RAPIDLY THIS EVENING...ESPECIALLY ALONG AND EAST OF THE I-95 CORRIDOR. EXPECT THE RAIN TO INCREASE NOT ONLY IN COVERAGE BUT ALSO IN INTENSITY OVERNIGHT AS STRONG UPPER LEVEL DIFLUENCE DEVELOPS AND LOW LEVEL FORCING STRENGTHENS DUE TO THE DEVELOPMENT OF A 35-50 KT LOW LEVEL JET WITH THE APPROACH OF THE COASTAL LOW. THE RAIN SHOULD BEGIN TO MIX WITH WET SNOW MAINLY WEST OF I-95 TOWARD DAYBREAK. ALTHOUGH SOME BANDING COULD SET UP BEFORE THE MOISTURE STRIPS OUT...STILL NOT ENOUGH CONFIDENCE TO ISSUE ANY WINTER WEATHER ADVISORIES. RAINFALL AMOUNTS TONIGHT WILL RANGE FROM ABOUT 1/10 INCH FAR INTERIOR SOUTHEAST GEORGIA TO AROUND 3/4 INCH IN THE CHARLESTON TRI-COUNTY AREA. THIS MUCH RAIN WILL NOT BE ENOUGH TO PRODUCE WIDESPREAD FLOODING...BUT LOCALIZED NUISANCE FLOODING IS CERTAINLY POSSIBLE GIVEN THE ALREADY SATURATED GROUNDS. THE AFOREMENTIONED LOW LEVEL JET WILL PRODUCE BREEZY CONDITIONS OVERNIGHT...WITH GUSTS REACHING 25-35 MPH AT TIMES NEAR THE IMMEDIATE COAST...ESPECIALLY IN CHARLESTON COUNTY. LAKE WINDS...A LAKE WIND ADVISORY IS IN EFFECT LATE TONIGHT DUE TO WINDS RESULTING FROM THE TIGHT PRESSURE GRADIENT AROUND THE ATLANTIC CYCLONE AND COLD ADVECTION ATOP THE WARMER WATERS OF LAKE MOULTRIE. && .SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY/... SUNDAY BEGINS WITH MAINLY RAIN...AND MORNING POPS AREA GRADUATED FROM CATEGORICAL ALONG/EAST OF INTERSTATE 95 TO SLIGHT CHANCE/CHANCE INLAND. WHILE COLD ADVECTION/DYNAMIC COOLING COULD SUPPORT RAIN MIXING WITH WET SNOWFLAKES JUST ABOUT ANYWHERE IN THE MORNING...THE COMMA CLOUD/ASSOCIATED DEEP LAYERED MOISTURE WILL ADVANCE TOWARD THE NORTHEAST AND WILL RESIDE LONGEST ACROSS SOUTH CAROLINA COUNTIES...ESPECIALLY ALONG AND NORTH OF THE EDISTO RIVER. HERE...FOCUSED FORCING FOR ASCENT COULD TRANSLATE TO RAIN MIXING WITH WET SNOW...AND THERE IS A LOW PROBABILITY THAT RAIN COULD CHANGE OVER TO WET SNOW IN SOME AREAS. IF PRECIPITATION BECOMES SIGNIFICANTLY CONVECTIVE...LOCALIZED HEAVIER BURSTS OF WET SNOW COULD DEPOSIT A QUICK COUPLE OF INCHES ACCUMULATION WHICH COULD TEMPORARILY PRODUCE SLICK ROADS WITHIN THE CHARLESTON QUAD-COUNTY REGION SUNDAY MORNING. HOWEVER...EVEN IF/WHERE SNOW TEMPORARILY ACCUMULATES...SNOW WILL MELT QUICKLY WHEN SNOW ENDS AND/OR CHANGES BACK TO RAIN. ALSO OF NOTE...12Z GUIDANCE HAS TRENDED SLIGHTLY WARMER WITHIN THE 1000-850 MB LAYER...AND THERE IS A DECENT CHANCE FOR MOST/ALL PRECIPITATION TO REMAIN LIQUID. GIVEN THE LOW PROBABILITY FOR HIGHLY LOCALIZED ACCUMULATING SNOW AND ONGOING UNCERTAINTY REGARDING PRECIPITATION TYPE...WINTER WEATHER HEADLINES ARE NOT WARRANTED. OTHERWISE...POPS WILL STEADILY DIMINISH AS DEEP LAYERED MOISTURE RETREATS TOWARD THE NORTHEAST SUNDAY AFTERNOON...AND POPS FALL TO LESS THAN 15 PERCENT SUNDAY NIGHT. ALSO OF NOTE...WINDS PRODUCED BY THE DEEPENING ATLANTIC LOW COULD PRODUCE WIND GUSTS AS HIGH AS 40 MPH ESPECIALLY NEAR THE CHARLESTON COUNTY COAST. AFTER COLLABORATION WITH WFO ILM...ISSUED A WIND ADVISORY FOR CHARLESTON COUNTY SUNDAY. MONDAY...TEMPERATURES COULD BRIEFLY PUSH INTO THE 55-60F RANGE BEFORE A STRONG COLD FRONT CROSSES THE REGION DURING THE AFTERNOON/EVENING. PER AREA CONSENSUS...MONDAY AFTERNOON FEATURES SLIGHT CHANCE POPS...ALTHOUGH DRY MODEL SOUNDINGS SUGGEST MOST LOCATIONS WILL REMAIN RAIN-FREE. AS COLD ADVECTION SURGES INTO THE REGION BENEATH AN UPPER TROUGH MONDAY NIGHT...CANNOT RULE OUT AN ISOLATED SNOW FLURRY OR TWO. OTHERWISE...EXPECT CHILLY LOWS IN THE 30S/WIND CHILLS IN THE 20S MONDAY NIGHT...FOLLOWED BY DRY...BRISK AND COLD CONDITIONS WITH HIGHS ONLY IN THE 40S TUESDAY. && .LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/... THE FORECAST AREA WILL REMAIN SOLIDLY UNDER THE INFLUENCE OF THE COLD TROUGH ALOFT THROUGH MID TO LATE WEEK. HIGH PRESSURE WILL GRADUALLY BUILD IN FROM THE WEST AND THE OVERALL FORECAST CONTINUES TO LOOK COOL AND DRY. IN FACT...TEMPERATURES WILL BE WELL BELOW NORMAL WEDNESDAY AND THURSDAY BEFORE MODIFYING TO NEAR NORMAL BY THE END OF THE WEEK AND THE START OF THE WEEKEND. && .AVIATION /04Z SUNDAY THROUGH THURSDAY/... CONDITIONS WILL DETERIORATE AT THE TERMINALS TONIGHT INTO SUNDAY MORNING AS LOW PRESSURE RAPIDLY INTENSIFIES OFF THE SOUTHEAST COAST. KCHS...RAIN WILL OVERSPREAD THE TERMINAL THIS EVENING AND BECOME MODERATE AT TIMES OVERNIGHT THROUGH EARLY SUNDAY AFTERNOON. THERE IS EVEN A LOW POTENTIAL FOR SOME WET SNOW TO MIX IN AT TIMES SUNDAY MORNING...BUT THE PROBABILITY IS TOO LOW TO INCLUDE IN THE TAF AT THIS TIME. THE RAIN SHOULD TAPER OFF BY LATE AFTERNOON AS THE LOW STARTS TO PULL AWAY TO THE NORTHEAST. AS FOR CEILINGS...EXPECT THEM TO LOWER TO MVFR LEVELS AND APPROACH IFR LEVELS AT TIMES OVERNIGHT. HOWEVER...IFR CEILINGS ARE MORE LIKELY TO PREVAIL IN THE 13-20Z TIME FRAME. GUSTY WINDS WILL ALSO BE AN ISSUE AT THE TERMINAL...WITH GUSTS UPWARDS OF 25-30 KT POSSIBLE AT TIMES OVERNIGHT THROUGH THE DAY SUNDAY. KSAV...RAIN WILL OVERSPREAD THE TERMINAL THIS EVENING AND BECOME MODERATE AT TIMES OVERNIGHT. AS THE RAIN TAPERS OFF SUNDAY MORNING AS THE LOW STARTS TO PULL AWAY TO THE NORTHEAST...THERE IS EVEN A LOW POTENTIAL FOR SOME WET SNOW TO MIX IN AT TIMES...BUT THE PROBABILITY IS TOO LOW TO INCLUDE IN THE TAF AT THIS TIME. AS FOR CEILINGS...EXPECT THEM TO PREVAIL AT MVFR LEVELS THROUGH MOST OF THE FORECAST PERIOD...BUT POSSIBLY APPROACH IFR LEVELS AT TIMES OVERNIGHT. GUSTY WINDS WILL ALSO BE AN ISSUE AT THE TERMINAL...WITH GUSTS UPWARDS OF AROUND 25 KT POSSIBLE AT TIMES OVERNIGHT THROUGH THE DAY SUNDAY. EXTENDED AVIATION OUTLOOK...VFR. && .MARINE... TONIGHT...STRENGTHENING LOW PRESSURE OFFSHORE WILL LEAD TO DETERIORATING MARINE CONDITIONS. NORTHERLY WINDS WILL CONTINUE TO STRENGTHEN OVERNIGHT...AND GALE WARNINGS ARE NOW IN EFFECT FOR ALL OF THE COASTAL WATERS FOR GUSTS APPROACHING 35-40 KT. A SMALL CRAFT ADVISORY REMAINS IN EFFECT FOR CHARLESTON HARBOR. SEAS SHOULD BUILD UPWARDS OF 5-8 FT ACROSS THE NEAR SHORE WATERS AND 7-11 FT ACROSS THE OUTER GEORGIA WATERS BY DAYBREAK. SUNDAY THROUGH THURSDAY...HAZARDOUS MARINE CONDITIONS WILL PREVAIL THROUGH SUNDAY AS OFFSHORE/PASSING LOW PRESSURE DEEPENS RAPIDLY AND GALES BECOME COMMON. A STORM WATCH HAS BEEN ISSUED FOR THE CHARLESTON COUNTY NEAR SHORE MARINE ZONE AS WINDS TOWARD 20 NM OFFSHORE COULD GUST TO STORM FORCE AT TIMES LATE SUNDAY MORNING AND SUNDAY AFTERNOON AS THE LOW MAKES ITS CLOSEST APPROACH AND THE GRADIENT TIGHTENS SIGNIFICANTLY. EVEN AS LOW PRESSURE PULLS AWAY SUNDAY NIGHT INTO MONDAY...ELEVATED WINDS AND SEAS WILL MAINTAIN SCA CONDITIONS MOST AREAS. THEN...IN THE WAKE OF A STRONG COLD FRONT...ANOTHER PERIOD OF GALES IS LIKELY MONDAY NIGHT INTO TUESDAY...ESPECIALLY NEAR 20 NM AND BEYOND. ELEVATED WINDS/SEAS SHOULD PERSIST INTO WEDNESDAY...THEN CONDITIONS SHOULD BEGIN TO IMPROVE AS HIGH PRESSURE EXPANDS INTO THE REGION BEGINNING THURSDAY. && .TIDES/COASTAL FLOODING... ASTRONOMICAL HIGH TIDES WILL SOON BE UPON US AND DEPARTURES ARE ALREADY RUNNING AS MUCH AS 1 FOOT ABOVE PREDICTED ALONG THE ENTIRE STRETCH OF THE COAST. THIS SUGGESTS AT LEAST A LOW END CHANCE OF SHALLOW COASTAL FLOODING WITH THE MORNING HIGH TIDES ALONG PARTS OF THE SC COAST FOR THE BEGINNING OF NEXT WEEK. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...NONE. SC...LAKE WIND ADVISORY FROM 4 AM TO 7 PM EST SUNDAY FOR SCZ045. WIND ADVISORY FROM 10 AM TO 7 PM EST SUNDAY FOR SCZ050. MARINE...GALE WARNING UNTIL 7 PM EST SUNDAY FOR AMZ352-354. STORM WATCH FROM 10 AM EST SUNDAY THROUGH SUNDAY EVENING FOR AMZ350. GALE WARNING UNTIL 10 AM EST SUNDAY FOR AMZ350. GALE WARNING UNTIL 10 PM EST SUNDAY FOR AMZ374. GALE WATCH FROM 10 AM EST SUNDAY THROUGH SUNDAY EVENING FOR AMZ330. SMALL CRAFT ADVISORY UNTIL 10 AM EST SUNDAY FOR AMZ330. && $$ NEAR TERM...JAQ SHORT TERM...SPR LONG TERM...BSH AVIATION...JAQ/SPR MARINE...JAQ/SPR TIDES/COASTAL FLOODING...SPR

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