Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 200249 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 949 PM EST FRI DEC 19 2014 .SYNOPSIS... CLOUDS WILL INCREASE TONIGHT AHEAD OF WEAK LOW PRESSURE THAT WILL MOVE ACROSS THE NORTHERN GULF OF MEXICO. THIS LOW WILL PASS OFF THE COAST SATURDAY BRINGING RAIN AND COOL TEMPERATURES. ANOTHER AREA OF LOW PRESSURE MOVING UP THE COAST WILL BRING MORE CLOUDS AND RAIN MONDAY AND TUESDAY. A LARGE LOW PRESSURE SYSTEM WILL PASS TO THE NORTHWEST WEDNESDAY AND DRIVE A STRONG COLD FRONT THROUGH THE CAROLINAS. COLD AND DRY WEATHER IS EXPECTED FOR THE END OF THE WEEK. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... AS OF 930 PM FRIDAY...HIGH CLOUDS ARE THICKENING ACROSS THE EASTERN CAROLINAS. THE LEADING EDGE OF THE MID-LEVEL DENSE OVERCAST SHOULD ARRIVE ALONG THE I-95 CORRIDOR SHORTLY AFTER MIDNIGHT. LATEST HIGH-RES MODELS LOOK VERY SIMILAR TO OUR PREVIOUS THOUGHTS WITH RAIN CHANCES INCREASING FROM THE SW LATE TONIGHT, BUT WITH THE BULK OF THE PRECIPITATION HOLDING OFF UNTIL AFTER DAYBREAK. POPS LATE TONIGHT HAVE BEEN TWEAKED DOWNWARD AGAIN ACROSS SE NORTH CAROLINA WITH LITTLE CHANGE ELSEWHERE. HOURLY TEMPERATURES ARE RUNNING A FEW DEGREES HIGHER THAN EARLIER PROJECTIONS, ESPECIALLY INLAND WHERE CLOUDS HAVE INTERFERED MOST WITH RADIATIONAL COOLING. FORECAST LOWS HAVE BEEN BUMPED UP IN RESPONSE WITH UPPER 30S ACROSS SE NORTH CAROLINA TO LOWER 40S ACROSS THE PEE DEE. PREVIOUS DISCUSSION FROM 630 PM FOLLOWS... RADAR COMPOSITES SHOW RAIN HAS ADVANCED AS FAR EAST AS EAST-CENTRAL ALABAMA. THIS MATCHES UP WELL WITH ANALYZED & FORECAST LIFT ON THE 300K-305K ISENTROPIC SURFACES. WHILE VIRTUALLY ALL MODEL GUIDANCE SHOWS MOIST LIFT DEVELOPING IN THE EASTERN CAROLINAS WITHIN THIS LAYER (10000-15000 FT) SHORTLY AFTER 06Z/1 AM EST...THERE WILL BE SIGNIFICANT DRY AIR BELOW THE CLOUD BASE TO OVERCOME. COMPARING VARIOUS MODELS MEAN RH IN THE 1000-700 MB LAYER AT 06, 09, AND 12Z THE GFS IS THE MOST MOIST WITH THE NAM THE DRIEST. 18Z GFS MOS POPS APPEAR TO BE TAKING THE DRY AIR QUITE SERIOUSLY...AND EYEBALLING FORECAST SOUNDINGS IT SHOULD TAKE A FAIRLY SIGNIFICANT AMOUNT OF RAIN TO MOISTEN THE LOW LEVELS. WITH THIS IN MIND I HAVE TRIMMED BACK POPS LATE TONIGHT ACROSS COASTAL SE NORTH CAROLINA WHERE MEASURABLE RAIN PROBABLY WON`T OCCUR UNTIL AFTER DAYBREAK. POPS HAVE ACTUALLY BEEN INCREASED FOR THE FLORENCE-DARLINGTON-KINGSTREE AREA LATE. NO SIGNIFICANT CHANGES TO TEMPERATURES HAVE BEEN MADE AS INCREASING CLOUD COVER WILL ALLOW MOST OF OUR TEMPERATURE DROP TO OCCUR THIS EVENING, WITH FAIRLY STEADY TEMPERATURES EXPECTED LATE TONIGHT. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY NIGHT/... AS OF 3 PM FRIDAY...COOL AND CLOUDY WEEKEND ON TAP WITH A SERIES OF WEAK SURFACE WAVES PASSING OFF THE SOUTHEAST COAST. THE FIRST ARRIVES EARLY SATURDAY MORNING...ASSOCIATED WITH WEAKENING 5H SHORTWAVE. THE SURFACE WAVE/LOW IS RATHER UNINSPIRING BUT DOES PROVIDE A DECENT AMOUNT OF LOW LEVEL MOISTURE. SURFACE HIGH RIDGING DOWN THE COAST ENHANCES ISENTROPIC LIFT...WHICH SHOULD BE ABLE TO TAP INTO THE AVAILABLE MOISTURE. THERE IS A PERIOD SAT INTO SAT EVENING WHERE DEEP MOISTURE...ASSOCIATED WITH THE SHORTWAVE...IS PRESENT. ALTHOUGH POP REMAINS IN THE LIKELY TO CATEGORICAL RANGE TOTAL QPF WILL BE LOW. RAIN WILL BE LIGHT WITH THE BULK OF THE PRECIP CONFINED TO THE COAST. SURFACE AND MID LEVEL FEATURES MOVE EAST SAT NIGHT FOLLOWED BY WEAK MID LEVEL SUBSIDENCE. ALTHOUGH DRYING OCCURS ALOFT THE LOW LEVELS REMAIN QUIET MOIST WITH THE WEDGE HOLDING STRONG. SKIES WILL REMAIN CLOUDY SAT NIGHT AND SUN WITH HIGHS RUNNING BELOW CLIMO AND LOWS NEAR CLIMO. ALTHOUGH NO MEASURABLE PRECIP IS EXPECTED SUN FORECAST SOUNDINGS DO SUGGEST THE POSSIBILITY OF PATCHY DRIZZLE...SOMETHING TO KEEP AN EYE ON. THE NEXT AND CURRENTLY BEST CHANCE AT SIGNIFICANT RAIN IN THE PERIOD WILL BE SUN NIGHT INTO MON. ANOTHER MORE SIGNIFICANT SURFACE WAVE MOVES UP THE BOUNDARY THAT WILL BE STALLED OFF THE COAST FOR MUCH OF THE PERIOD. SURFACE HIGH CONTINUES PUSHING DOWN THE COAST AS THE LOW AND ITS ASSOCIATED MOISTURE MOVES NORTHEAST. INCREASING ISENTROPIC LIFT IN AN AREA OF INCREASE DEEP MOISTURE...PRECIPITABLE WATER VALUES EXCEED 1.25 INCH BY THE END OF THE PERIOD...SHOULD LEAD TO RAIN DEVELOPING ACROSS MUCH OF THE AREA BY MON MORNING. CLOUD COVER AND NORTHERLY FLOW WILL KEEP LOWS NEAR TO SLIGHTLY ABOVE CLIMO. && .LONG TERM /MONDAY THROUGH FRIDAY/... AS OF 3 PM FRIDAY...LOOKS LIKE RAIN WILL BE ONGOING AT THE START OF THE LONG TERM PERIOD. SHALLOW COOL AIR WILL BE IN PLACE THROUGH THE MORNING WITH A NORTHEAST FLOW AT THE SFC AS HIGH PRESSURE REMAINS WEDGED IN THROUGH INLAND CAROLINAS. AN AREA OF LOW PRESSURE WILL MOVE UP THE SOUTHEAST COAST THROUGH THE DAY WITH A TROUGH EXTENDING NE FROM THE LOW JUST OFF SHORE IN A MORE TYPICAL WEDGE LIKE SCENARIO. AS THE LOW MOVES FARTHER NORTH BY MON AFTERNOON THE COASTAL TROUGH WILL GET PUSHED INLAND SLIGHTLY DRIVING WARMER TEMPS AND MORE SHOWERY WEATHER INTO COASTAL AREAS. ITS ALWAYS TOUGH TO TIME WHEN THIS WILL OCCUR BUT FOR NOW WILL SHOW A TREND OF WARMING ALONG THE COAST. PCP MAY BE MORE INTERMITTENT AS THE LOW TRACKS NORTH AND COASTAL CAROLINAS END UP IN A NW FLOW ON THE BACK END INITIALLY FOLLOWED BY A DEEPER WARMER AND MOISTER SOUTHERLY FLOW ON TUES AHEAD OF NEXT SYSTEM. THEREFORE SHALLOW COOL AIR IN PLACE MON MORNING WILL BE REPLACED BY DEEPER WARMER AIR BRIEFLY ALONG THE COAST AND THEN COOLER AIR THROUGH MON NIGHT. DEEPER SOUTHERLY FLOW WILL SET UP ON TUES AHEAD OF NEXT STORM SYSTEM SHIFTING EAST FROM THE MISSISSIPPI VALLEY. UNSETTLED WEATHER WILL REMAIN AHEAD OF THIS SYSTEM THROUGH TUES INTO WED BEFORE COLD FRONT MOVES THROUGH LATE WED. THE DIGGING MID TO UPPER TROUGH WILL FINALLY MOVE OFF SHORE BY THURS MORNING LEAVING DRIER AND COOLER WEATHER FOR CHRISTMAS DAY. OVERALL EXPECT CLOUDY AND DAMP TO WET WEATHER THROUGH THE FIRST HALF OF THE PERIOD WITH COOLER MORE SEASONABLE WEATHER THURS INTO FRI AS HIGH PRESSURE BUILDS ACROSS THE SOUTH. TEMPS WILL START OUT COOL BUT WILL WARM AS COASTAL TROUGH/WARM FRONT PUSHES INLAND LATE MONDAY INTO TUES. TIGHT GRADIENT WILL EXIST ON MON BETWEEN COOLER TEMPS INLAND...IN THE 40S MOST PLACES...TO POSSIBLE 60S ALONG THE COAST. BY TUES THE WARMER AIR SHOULD MAKE IT INTO THE WESTERN REACHES OF LOCAL FORECAST AREA LEAVING TEMPS CLOSER TO 60 MOST PLACES FOR TUES AND WED UNTIL COLD FRONT MOVES THROUGH BY THURS. && .AVIATION /00Z SATURDAY THROUGH WEDNESDAY/... AS OF 00Z...VFR CONDITIONS TONIGHT WILL DETERIORATE INTO SAT MORNING AS RAIN OVERSPREADS THE EASTERN CAROLINAS. CURRENT SATELLITE IMAGERY INDICATES MID/HIGH CLOUDS WILL CONTINUE INCREASING IN COVERAGE OVERNIGHT AHEAD OF AN UPPER DISTURBANCE. MOIST ISENTROPIC LIFT WILL BRING -RA AND LOWERING CIGS FROM SOUTH TO NORTH BEGINNING AROUND DAYBREAK. DRY AIR IN THE LOWER LEVELS WILL INITIALLY KEEP CIGS VFR...BUT AS RAIN CONTINUES TO FALL...CIGS WILL LIKELY DROP TO MVFR LEVELS BY AROUND MIDDAY. GFS SOUNDINGS HINT AT THE POSSIBILITY OF IFR CIGS ESPECIALLY ALONG THE COAST...BUT FOR NOW WILL KEEP ALL TERMINALS ABOVE 1KFT. WINDS ON SAT WILL BE NORTHEAST AOB 10 KT. RAIN SHOULD TAPER OFF AT THE INLAND SITES BY 21Z...ALTHOUGH LOW CLOUDS WILL HANG AROUND AREA WIDE THROUGH THE END OF THE PERIOD. EXTENDED OUTLOOK...MVFR CIGS POSSIBLE ON SUN. RAIN LIKELY MON WITH MVFR/IFR CONDITIONS AS A COASTAL TROUGH DEVELOPS OFFSHORE. MORE SHOWERS EXPECTED TUE/WED AHEAD OF A STRONG COLD FRONT. GUSTY WINDS WILL DEVELOP DURING THE DAY WED. && .MARINE... NEAR TERM /THROUGH TONIGHT/... AS OF 930 PM FRIDAY...NO CHANGES ARE NECESSARY TO THE FORECAST. PREVIOUS DISCUSSION FROM 630 PM FOLLOWS... ADJUSTED INITIAL SEA HEIGHTS DOWN SLIGHTLY IN THE GRIDDED FORECAST DATABASE GIVEN CURRENT OBSERVATIONS OF NOTHING HIGHER THAN 1 FOOT WITHIN 20 MILES OF SHORE. NE WINDS SHOULD GRADUALLY BUILD SEAS TO 2 FEET OVERNIGHT WITH 3 FOOTERS STARTING TO SHOW UP BY DAYBREAK. SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... AS OF 3 PM FRIDAY...HIGH PRESSURE CONTINUES TO BUILD DOWN THE COAST THROUGH THE PERIOD WHILE A SERIES OF WEAK SURFACE WAVES/LOWS PASS EAST OF THE WATERS. THE RESULT WILL BE A SLIGHTLY PINCHED GRADIENT AND NORTHEAST FLOW OF 10 TO 15 KTS...WITH POTENTIAL FOR BRIEF PERIODS OF 15 TO 20 KT. EXTENDED PERIOD OF NORTHEAST FLOW WILL BUILD SEAS TO 2 TO 4 FT FOR MUCH OF THE WATERS. EXCEPTION WILL BE LOCATIONS SHELTERED TO NORTHEAST FLOW OR WITH AN OFFSHORE COMPONENT. HERE SEAS WOULD BE 1 TO 2 FT. LONG TERM /MONDAY THROUGH WEDNESDAY/... AS OF 330 PM FRIDAY...LOW PRESSURE WILL MOVE UP THE SOUTHEAST COAST ON MONDAY. AN ELONGATED TROUGH WILL EXTEND UP THROUGH THE WATERS WITH NORTHEAST FLOW ON THE WEST SIDE AND SOUTHERLY FLOW ON THE EAST SIDE. AS THE LOW MOVES NORTH THERE MAY BE A PERIOD OF SOUTHERLY WINDS ACROSS ALL OF THE WATERS BUT OVERALL EXPECT MORE VARIABLE WINDS AT 10 TO 15 KTS. MAY SEE WINDS COME BACK AROUND TO OFF SHORE AS THE LOW MOVES UP THE COAST BUT A DEEPER SOUTHERLY FLOW WILL SET UP AHEAD OF NEXT SYSTEM BY TUES. AS THIS LARGE AND POTENT STORM SYSTEM PUSHES A COLD FRONT EAST THE GRADIENT WILL TIGHTEN TUES INTO WED WITH WINDS UP TO 15 TO 20 KTS. THIS WILL PUSH SEAS UP FROM 2 TO 4 FT TO 3 TO 5 FT BY LATE TUES. WNA SHOWS SEAS RAMPING UP ABOVE 6 FT BY WED MORNING AND POSSIBLE UP TO 7 TO 8 FT IN OUTER WATERS IN STRONGER SW TO W FLOW AS FRONT MOVES THROUGH THE WATERS ON WED. EXPECT SMALL CRAFT CONDITIONS MAINLY ON WED AND LASTING INTO THURS. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...NONE. && $$ NEAR TERM...TRA SHORT TERM...III LONG TERM...RGZ AVIATION...BJR

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