Issued by NWS Columbia, SC
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-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --000 FXUS62 KCAE 221501 AAA AFDCAE AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE COLUMBIA SC 1001 AM EST SUN NOV 22 2009 .SYNOPSIS... A LOW PRESSURE SYSTEM ALONG THE GULF COAST REGION WILL MOVE SLOWLY NORTHEAST ACROSS THE FLORIDA PANHANDLE TODAY THEN REFORM ALONG THE CAROLINA COAST TONIGHT. HIGH PRESSURE WILL WEDGE INTO THE CAROLINAS FROM THE NORTH. THIS PATTERN WILL BRING CLOUDS AND RAIN TO THE AREA THROUGH MONDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...-- Changed Discussion --A DEEP UPPER LOW CONTINUES TO LIFT NORTHEAST ACROSS MISSISSIPPI THIS MORNING WHILE STRONG HIGH PRESSURE AT THE SURFACE STRENGTHENS AS IT RIDGES DOWN THE EAST COAST. MOISTURE FLUX AND WARM ADVECTION ARE MAXIMIZED EAST OF THE UPPER LOW AND RESULTING IN A BAND OF RAIN EXTENDING FROM NORTH GEORGIA SOUTHEASTWARD TOWARDS SAVANNAH. THIS BAND OF RAIN WILL CONTINUE LIFTING NORTH THROUGH THE LATE MORNING AND EARLY AFTERNOON HOURS...SPREADING RAIN ACROSS THE FORECAST AREA. TEMPERATURES WILL STRUGGLE TO RISE MUCH TODAY WITH CONTINUED NORTHEASTERLY FLOW AND PRECIPITATION MOVING OVER THE AREA...WHICH WILL ENHANCE A DEVELOPING COLD AIR DAMMING WEDGE THAT IS DEVELOPING. IT IS DIFFICULT TO FIGURE OUT HOW MUCH MORE PRECIPITATION WILL DEVELOP BEHIND THIS INITIAL BAND AS THERE WILL BE SOME DYNAMICS AVAILABLE AS THE LOW LIFTS OUT BUT A SIGNIFICANT DRY AIR INTRUSION IS WRAPPING UNDERNEATH THE UPPER LOW AND PUSHING ITS WAY INTO CENTRAL GEORGIA AT THIS TIME AND WILL MOVE INTO THE FORECAST AREA BY LATE AFTERNOON. THIS LACK OF MOISTURE IN THE MID AND UPPER LEVELS WILL LIKELY DECREASE THE CHANCE OF SIGNIFICANT RAINFALL ACCUMULATION LATE AFTERNOON AND OVERNIGHT BUT LIGHT SHOWERS WILL LINGER AND DRIZZLE SHOULD DEVELOP OVERNIGHT. CLOUDS WILL REMAIN THROUGH THE DAY AS CEILINGS GRADUALLY LOWER AS THE ATMOSPHERE MOISTENS UP. MADE SOME CHANGES TO THE POP GRIDS TO ACCOUNT FOR SLIGHTLY FASTER TIMING IN THE WARM ADVECTION BUT THE OVERALL CHANGE IN THE FORECAST IS NOT GOING TO BE VERY SIGNIFICANT. WILL UPDATE THE ZONE FORECAST TO REMOVE MORNING WORDING.-- End Changed Discussion --&& .SHORT TERM /6 PM THIS EVENING THROUGH TUESDAY/... WEAKENING SHORT WAVE WILL CROSS GEORGIA INTO THE CAROLINAS TONIGHT. LOW PRESSURE DEVELOPING ON AN INVERTED TROUGH OFF THE SC COAST. KEPT CATEGORICAL POPS THROUGH EARLY TONIGHT THEN DIMINISHING AS ISENTROPIC LIFT SHIFTS NORTH AND WEST. RAINFALL AMOUNTS RANGING FROM ONE HALF INCH TO AROUND ONE INCH. THE SURFACE LOW WILL MOVE AWAY FROM THE COAST MONDAY WITH RAIN CHANCES DECREASING. KEPT CHANCE OF DRIZZLE IN FOR MONDAY NIGHT INTO TUESDAY WITH WEDGE POSSIBLY HOLDING AND HIGH LOW-LEVEL MOISTURE SUGGESTED BY MODEL T-SECTIONS. COOLER THAN MOS GUIDANCE MAXIMUM TEMPERATURE FORECAST DUE TO WEDGE. && .LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/... MEDIUM RANGE MODELS DEPICT A SERIES OF MID/UPPER LEVEL LOWS MOVING ACROSS THE UPPER MIDWEST TO THE EASTERN GREAT LAKES AND SOUTHEASTERN CANADA TUESDAY NIGHT INTO SATURDAY. ALL IN ALL, SLIGHT UPPER RIDGING OVER THE SOUTHEAST PART OF THE COUNTRY TUESDAY IS REPLACED BY A LARGE UPPER TROUGH OVER THE EASTERN UNITED STATES WEDNESDAY THROUGH FRIDAY. UPPER TROUGH FINALLY MOVES OFF THE EAST COAST SATURDAY. SURFACE HIGH PRESSURE CENTERED OVER SOUTHEASTERN CANADA TUESDAY NIGHT RIDGING INTO THE AREA FROM THE NORTH. SURFACE LOW PRESSURE CROSSING THE GREAT LAKES REGION ON THANKSGIVING DAY WILL DRAG A COLD FRONT ACROSS THE AREA. MOISTURE APPEARS LIMITED SINCE THE BEST ISENTROPIC LIFT REMAINS SOUTH AND EAST OF THE FORECAST AREA. ANY CHANCE FOR RAIN (WHICH IS SLIGHT) LOOKS LIKE WEDNESDAY INTO THURSDAY MORNING. COOL HIGH PRESSURE BUILDS IN FOR FRIDAY AND SATURDAY. WILL KEEP THE EXTENDED FORECAST DRY. SEASONABLY MILD MAX TEMPERATURES WEDNESDAY AND THURSDAY COOL A FEW DEGREES BELOW NORMAL FOR FRIDAY AND SATURDAY. NIGHTTIME LOWS IN THE 40S MID-WEEK COOLING TO THE MID AND UPPER 30S BY LATE NEXT WEEK. && .AVIATION /15Z SUNDAY THROUGH THURSDAY/...-- Changed Discussion --HIGH PRESSURE OVER THE MID-ATLANTIC STATES AND NEW ENGLAND WILL MOVE SLOWLY OFFSHORE THROUGH MONDAY. AN AREA OF LOW LOW PRESSURE ALONG THE GULF OF MEXICO WILL WEAKEN AS IT MOVES NORTHEAST TOWARD THE REGION. 88D REGIONAL COMPOSITE SHOWS A LARGE AREA OF LIGHT/MODERATE RAIN STRETCHING FROM ALABAMA ACROSS GEORGIA. THE NORTHERN EDGE WAS ALONG THE CSRA THIS MORNING. AS THE AREA OF LOW PRESSURE GRADUALLY MOVES NE...EXPECT THE SHIELD OF PCPN TO GRADUALLY MOVE INTO THE REGION THROUGH THE MORNING HOURS. CURRENTLY ALL TAF SITES INDICATING VFR CONDITIONS...BUT CONDITIONS WILL GRADUALLY DIMINISH THROUGH THE MORNING HOURS AND EXPECT MVFR CONDITIONS TO DEVELOP BETWEEN 17-18Z. TIME SECTIONS SHOW ABUNDANT LOW LEVEL MOISTURE THROUGH THE PERIOD ALONG WITH INCREASING ISENTROPIC LIFT THIS AFTERNOON AND LASTING INTO MONDAY. EXPECT CONDITIONS TO BECOME IFR/LIFR THIS EVENING AND REMAIN THROUGH THE REST OF THE PERIOD...MAINLY DUE TO LOW CIGS. EXPECT RAIN THROUGH THE DAY TO TAPER OFF TO DRIZZLE AND CONTINUE THROUGH THE PERIOD. EXTENDED AVIATION OUTLOOK...WIDESPREAD MVFR OR IFR CONDITIONS WILL CONTINUE MONDAY AND MONDAY NIGHT AND PERHAPS EVEN INTO TUESDAY. LOW PRESSURE IS EXPECTED TO WEAKEN AS IT MOVES TOWARD THE AREA...THEN REFORM ALONG THE NC/VA COAST. HOWEVER...HIGH PRESSURE IS EXPECTED TO CONTINUE WEDGED IN ACRS THE REGION INTO TUESDAY...CONDITIONS SHOULD IMPROVE TO VFR BY LATE TUESDAY.-- End Changed Discussion --&& .CAE WATCHES/WARNINGS/ADVISORIES... SC...NONE. GA...NONE. && $$ NEAR TERM...HC
