Area Forecast Discussion
Issued by NWS Columbia, SC

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000 FXUS62 KCAE 221852 AFDCAE AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE COLUMBIA SC 152 PM EST MON DEC 22 2014 .SYNOPSIS... A FRONTAL ZONE WILL REMAIN NEAR THE SOUTHEAST COAST THROUGH TUESDAY. A SERIES OF LOW PRESSURE SYSTEMS WILL MOVE NORTHEASTWARD ALONG THE FRONT...KEEPING WEATHER UNSETTLED. A STRONG COLD FRONT APPROACHING FROM THE WEST WILL MOVE THROUGH THE FORECAST AREA WEDNESDAY NIGHT. && .NEAR TERM /THROUGH TONIGHT/... DEEP UPPER TROUGH OVER THE CENTRAL CONUS WILL CONTINUE TO PROMOTE SOUTHWESTERLY FLOW ALOFT. AT THE SURFACE...HIGH PRESSURE CENTERED OVER NEW ENGLAND WILL CONTINUE RIDGING INTO THE FORECAST AREA PROMOTING A STRONG COLD AIR DAMMING SETUP. SURFACE ANALYSIS SHOWS AN AREA OF LOW PRESSURE CENTERED OVER THE NORTH CAROLINA COAST WHICH IS PROMOTING INCREASED MOISTURE INTO THE AREA. MESOSCALE BRIEFING INDICATES THE HIGHEST PRECIPITABLE WATER AND BEST MOISTURE TRANSPORT ACROSS THE EAST. ISENTROPIC LIFT OVER THE WEDGE RIDGE WILL SUPPORT RAIN OR DRIZZLE INTO THE OVERNIGHT PERIOD. REGIONAL RADAR COMPOSITE SHOWS AN AREA OF SHOWERS MOVING NORTHEAST ACROSS THE CENTRAL AND EASTERN PART OF THE FORECAST AREA THIS AFTERNOON WITH MORE WIDESPREAD SHOWERS AND EMBEDDED THUNDERSTORMS FURTHER SOUTH AND EAST ALONG COASTAL SC/GA AND ACROSS THE FLORIDA PANHANDLE. HAVE SEEN SOME LIGHTNING IN THE EASTERN MIDLANDS DUE TO INSTABILITY ALOFT. FOR MOST OF THE FORECAST AREA...THE MAIN PRECIPITATION TYPE WILL BE OCCASIONAL DRIZZLE. MODELS INDICATE 0.15 INCH OF RAIN OR LESS WITH THE HIGHEST AMOUNTS EAST. TEMPERATURES WILL REMAIN STEADY IN THE 40S THROUGH THE AFTERNOON AND WILL MAKE LITTLE CHANGE OVERNIGHT UNDER CLOUD COVER. && .SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... THE CHANCE OF MEASURABLE RAIN SHOULD BE ON THE INCREASE TUESDAY. THE MODELS ARE CONSISTENT INDICATING DEEPER MOISTURE WITH THE H5 HEIGHTS BACKING. THERE WILL BE ISENTROPIC UPGLIDE. LIFT ASSOCIATED WITH THE RIGHT ENTRANCE REGION OF THE H25 JET MAY ALSO AFFECT THE AREA. THE NAM AND GFS MOS HAVE LIKELY OR CATEGORICAL POPS. USED THE COOLER NAM MOS HIGH TEMPERATURES BECAUSE OF THE WEDGE PATTERN. THE NAM SURFACE-BASED LI PATTERN SUGGESTS THE WEDGE WILL HOLD THROUGH TUESDAY NIGHT. THE AREA SHOULD CONTINUE UNDER THE MOIST CONVEYOR BELT WITH ISENTROPIC UPGLIDE AND LIFT ASSOCIATED WITH THE RIGHT ENTRANCE REGION OF THE UPPER JET. THE NAM...GFS...AND ECMWF MOS ARE IN GOOD AGREEMENT WITH CATEGORICAL POPS. THE NAM AND GFS DISPLAY RAINFALL OF ONE-HALF TO ONE INCH. EXPECT LITTLE CHANGE IN TEMPERATURE OVERNIGHT. THE SHOWER CHANCE WILL REMAIN HIGH WEDNESDAY AND WEDNESDAY NIGHT. THE MODELS DISPLAY CONTINUED DEEP MOISTURE. THE NAM SURFACE-BASED LI PATTERN SUGGESTS THE WARM FRONT MAY LIFT INTO THE FORECAST AREA WEDNESDAY AHEAD OF THE STRONG COLD FRONT BUT STILL ONLY LOWERS LI/S TO AROUND 1 IN THE EXTREME SOUTH PART. THE COLDER UPPER-AIR TEMPERATURES APPEAR TO REMAIN TO THE WEST AND WITH WIDESPREAD RAIN THE LACK OF SIGNIFICANT INSTABILITY AS FORECAST BY THE MODELS APPEARS REASONABLE. THE THUNDERSTORM CHANCE APPEARS LOW AT THIS TIME. USED THE GUIDANCE CONSENSUS FOR THE TEMPERATURE FORECAST WEDNESDAY BUT CONFIDENCE IS LOW BECAUSE OF UNCERTAINTY WITH THE PLACEMENT OF THE WARM FRONT. THE MODELS SHOW THE COLD FRONT MOVING THROUGH THE FORECAST AREA WEDNESDAY NIGHT. THE NAM WAS A LITTLE SLOWER WITH THE FRONTAL TIMING COMPARED TO THE GFS AND ECWMF BUT ALL OF THE MODELS INDICATED THE FRONT THROUGH THE AREA WITH DRYING BEFORE ABOUT 400 AM CHRISTMAS MORNING. EXPECT BREEZY CONDITIONS BEHIND THE FRONT. && .LONG TERM /THURSDAY THROUGH MONDAY/... THE MODELS CONTINUE TO SHOW A DRY AIR MASS FOR CHRISTMAS DAY. IF MAY REMAIN BREEZY...BUT THE MODELS INDICATE A DIMINISHING PRESSURE GRADIENT AS THE RIDGE GETS CLOSER TO THE AREA. THE GFS...ECWMF...AND EKD MOS SUPPORTS HIGHS IN THE UPPER 50S TO AROUND 60 BUT BREEZY CONDITIONS SHOULD MAKE IT FEELER COOLER. THE RIDGE SHOULD BE OVER THE AREA THURSDAY NIGHT. STRONG NOCTURNAL COOLING SHOULD OCCUR WITH MOSTLY CLEAR SKIES AND LIGHT WINDS. THE GFS AND ECWMF MOS HAVE LOWS MAINLY IN THE LOWER 30S. THE DRY RIDGE SHOULD CONTINUE TO DOMINATE FRIDAY. MOISTURE MAY INCREASE ASSOCIATED WITH ANOTHER COLD FRONT MOVING INTO THE AREA SATURDAY OR SUNDAY. THE GFS AND ECMWF MOS POPS WERE 20 TO 40 PERCENT WITH THE ECMWF INDICATING THE GREATER SHOWER CHANCE. && .AVIATION /18Z MONDAY THROUGH SATURDAY/... IFR CONDITIONS EXPECTED THROUGH THE 24 HOUR TAF PERIOD. LIGHT RAIN/DRIZZLE STILL CONTINUING AT THE TAF SITES THIS AFTERNOON. REGIONAL RADAR COMPOSITE SHOWS PATCHY LIGHT RAIN MOVING NORTHEAST ACROSS SOUTHEASTERN GEORGIA WHICH WILL REACH THE TAF SITES LATE THIS AFTERNOON. CONDITIONS NOT EXPECTED TO IMPROVE AS NORTHEASTERLY FLOW CONTINUES TO PROMOTE WEDGE CONDITIONS. EXPECT LIGHT RAIN/DRIZZLE TO REDUCE VSBYS INTO THE MVFR RANGE WITH CIGS MAINLY IFR THROUGH THE AFTERNOON...AND IFR CIGS/VSBYS THIS EVENING. MODELS INDICATE LIFR CIGS LATE TONIGHT THROUGH THE END OF THE TAF PERIOD. MAY SEE IMPROVEMENT FROM LIFR TO IFR TOWARD THE END OF THE TAF PERIOD ALTHOUGH MODELS OFTEN SHOW IMPROVEMENT TOO QUICKLY SO HAVE KEPT LIFR CONDITIONS THROUGH 18Z TUESDAY. WINDS THROUGH THE PERIOD WILL BE NORTHEASTERLY AT 7 KNOTS OR LESS FOR MUCH OF THE PERIOD. EXTENDED AVIATION OUTLOOK...WIDESPREAD MVFR TO IFR CONDITIONS EXPECTED TUESDAY THROUGH WEDNESDAY EVENING AS A SERIES OF SYSTEMS CROSS THE REGION. BREEZY CONDITIONS POSSIBLE WEDNESDAY AFTERNOON INTO THURSDAY MORNING. && .CAE WATCHES/WARNINGS/ADVISORIES... SC...NONE. GA...NONE. && $$

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