Area Forecast Discussion
Issued by NWS Charleston, SC

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000 FXUS62 KCHS 221315 AFDCHS AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHARLESTON SC 915 AM EDT WED OCT 22 2014 .SYNOPSIS... HIGH PRESSURE WILL BUILD INTO GEORGIA AND SOUTH CAROLINA TODAY AND THEN DOMINATE INTO NEXT WEEK. && .NEAR TERM /THROUGH TONIGHT/...
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TODAY...MUCH COOLER AND DRYER AIR WILL PUSH INTO THE REGION BEHIND A COLD FRONT OFF THE SOUTHEAST COAST. THE PATTERN FAVORS HIGH TEMPS SOME 8-10 DEGREES COOLER THAN THE PREVIOUS DAY AS A NORTH/NORTHWEST FLOW PERSISTS BETWEEN HIGH PRESSURE CENTERED OVER THE MIDWEST AND A BROAD LOW PRESSURE SYSTEM JUST OFF THE MID-ATLANTIC AND NORTHEAST COAST. DESPITE A FULL DAY OF SUN...HIGH TEMPS SHOULD ONLY PEAK IN THE LOW 70S...WARMEST OVER SOUTHEAST GEORGIA. TONIGHT...INLAND AREAS SHOULD DECOUPLE QUICKLY AFTER SUNSET THIS EVENING BUT LIGHT NORTHERLY SURFACE WINDS COULD KEEP GOING INTO THE NIGHT RIGHT ALONG THE COAST...INCLUDING BEACHES AND BARRIER ISLANDS. THIS WILL ALLOW FOR STRONG RADIATIONAL COOLING WEST OF U.S. 17 WITH SOME NORMALLY COLDER RURAL/INLAND AREAS NEARING 40 DEGREES BY DAWN ON THURSDAY. LOW MOST AREAS IN THE LOW TO MID 40S AWAY FROM THE OCEAN.
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&& .SHORT TERM /THURSDAY THROUGH SATURDAY/... THURSDAY...A DEEP LAYER RIDGE...CENTERED FROM THE GREAT LAKES SOUTHWARD TO THE GULF COAST...WILL BE THE DOMINANT FEATURE. AT THE SURFACE...LIGHT NORTH-NORTHWEST WINDS.THERE COULD BE A WEAK SEA BREEZE RIGHT AT THE COAST BY LATE AFTERNOON. THE COOLEST TEMPERATURES OF THIS PERIOD WITH HIGHS ONLY IN THE LOWER 70S AND LOWS IN THE LOWER TO MID 40S INLAND TO THE LOWER 50S AT THE COAST. FRIDAY...GLOBAL MODELS ALREADY HAVE SOME DIFFERENCES WITH THE EVOLUTION OF THE NEXT UPPER TROUGH THAT MOVES DOWN IN THE UPPER LEVEL NORTHWEST FLOW. THE ECMWF SEEMS TO BE THE OUTLIER WITH PRODUCING A MUCH STRONGER SHORT WAVE THAT APPROACHES THE REGION BY LATE DAY...WITH THE NAM AND THE GFS MUCH WEAKER/BROAD AND FURTHER NORTH. HAVE GONE WITH THE WEAKER SOLUTIONS AND KEPT OUT ANY MENTION OF PRECIP. AGAIN...LOW LEVEL FLOW WILL BE LIGHT NORTHWEST...WITH A LATE DAY SEA BREEZE POSSIBLE NEAR THE COAST. NOTE: SEA BREEZES ARE GETTING MORE DIFFICULT GIVEN TEMPERATURE DIFFERENCES BETWEEN THE LAND AND WATER ARE BECOMING LESS...EVEN WITH HIGHS IN THE MID 70S. FRIDAY NIGHT...LIGHT NORTHERLY LOW LEVEL FLOW WITH A SURFACE RIDGE NORTHWEST OF THE AREA OVER THE TN RIVER VALLEY. EXPECT TEMPS TO RADIATE DOWN TO THE MID 40S INLAND AND LOWER 50S COAST. SATURDAY...CONTINUED BROAD NORTHWEST UPPER LEVEL FLOW WITH A SURFACE RIDGE CENTERED WEST-NORTHWEST OF THE AREA. UPPER LEVEL HEIGHTS/TEMPS MODERATE SOME. THUS...EXPECT SLIGHTLY WARMER MAX TEMPS IN THE MID TO UPPER 70S WITH SUNNY SKIES. && .LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/... GLOBAL MODELS IN GOOD AGREEMENT THROUGH MONDAY THEN START TO DIVERGE. A SPRAWLING DEEP LAYER RIDGE BUILDS IN FROM THE WEST SUNDAY AND THEN MOVES JUST OFF SHORE BY LATER MONDAY AS AN ANOTHER UPPER TROUGH TAKES SHAPE OVER THE CENTRAL U.S. THIS NEXT TROUGH IS WHERE THE MODELS DIVERGE. THE ECMWF IS SLOWER AND MORE FULL LATITUDE IN ITS EXTENT BY TUESDAY...WHILE THE GFS IS WEAKER AND FASTER...HOLDING THE BULK OF THE ENERGY WELL NORTH OVER THE GREAT LAKES. ODDLY... MODELS COME BACK TO CLOSER AGREEMENT BY WEDNESDAY AS BOTH SHOW A BROAD TROUGH/NEARLY ZONAL FLOW OVER THE CENTRAL AND EASTERN U.S. AND A DEEP LAYER RIDGE DEPARTING OVER THE ATLANTIC. THROUGH THIS PERIOD...GLOBAL MODELS KEEP THE MAIN TROPICAL MOISTURE ASSOCIATED WITH TD9...CURRENTLY OVER THE BAY OF CAMPECHE...WELL SOUTH OF THE AREA. EXPECT ABOVE NORMAL TEMPERATURES THROUGH THIS PERIOD AS A DEEP LAYER RIDGE LARGELY DOMINATES. MONDAY THROUGH WEDNESDAY...LOW LEVEL FLOW VEERS TO SOUTHEAST...WHICH WILL HELP TO ADVECT BETTER LOW LEVEL MOISTURE INTO THE AREA. THUS...HAVE CONTINUED TREND OF SLIGHT CHANCE POPS FOR SHOWERS OVER MAINLY THE COASTAL AND ATLANTIC WATERS. && .AVIATION /13Z WEDNESDAY THROUGH SUNDAY/... VFR. NORTH WINDS MAY BE A BIT GUSTY INTO EARLY AFTERNOON BEFORE DIMINISHING AFTER MID AFTERNOON. EXTENDED AVIATION OUTLOOK...VFR CONDITIONS EXPECTED TO PREVAIL THROUGH THE REST OF THE WEEK AND INTO THE WEEKEND FOR BOTH KCHS AND KSAV. && .MARINE...
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TODAY...A DRY COLD FRONT WILL CONTINUE TO SHIFT EAST OVER THE WESTERN ATLANTIC...RESULTING IN A FAIR AMOUNT OF COLD AIR ADVECTION OVER THE COASTAL WATERS LATE THIS MORNING AS HIGH PRESSURE BUILDS FROM THE NORTHWEST. AS A RESULT...WINDS/SEAS WILL BE ENHANCED THROUGH LATE MORNING WITH NORTH/NORTHWEST WINDS RANGING BETWEEN 15-20 KTS AND SEAS BETWEEN 3-5 FT...HIGHEST IN OFFSHORE GEORGIA WATERS. THERE IS A CHANCE WE COULD SEE A PERIOD OF OCCASIONAL 25 KT WIND GUSTS OVER NORTHERN SC WATERS AND OFFSHORE WATERS THROUGH LATE MORNING...BUT SMALL CRAFT ADVISORIES ARE NOT ANTICIPATED. WINDS AND SEAS WILL STEADILY IMPROVE THIS AFTERNOON AND TONIGHT WHILE THE PRESSURE GRADIENT SLIGHTLY RELAXES OVER THE WATERS. THURSDAY THROUGH MONDAY...HIGH PRESSURE WILL REMAIN NORTHWEST OF THE REGION THROUGH SUNDAY THEN SHIFT TO NORTH AND EAST OF THE AREA BY LATER MONDAY. NO HIGHLIGHTS ARE EXPECTED THROUGH EARLY NEXT WEEK WITH WINDS 15 KT OR LESS AND SEAS 4 FT OR LESS.
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&& .CHS WATCHES/WARNINGS/ADVISORIES... GA...NONE. SC...NONE. MARINE...NONE. && $$ NEAR TERM...DPB SHORT TERM...RFM LONG TERM...RFM AVIATION...DPB MARINE...DPB/RFM

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