Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 212326 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 626 PM EST SUN DEC 21 2014 .SYNOPSIS...
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RAIN IS EXPECTED TONIGHT AS LOW PRESSURE MOVES ALONG THE CAROLINA COAST. HIGH PRESSURE WILL BRING COOL AND CLOUDY CONDITIONS INTO TUESDAY. AN APPROACHING AND STRONG COLD FRONT WILL BRING SHOWERS AND A FEW THUNDERSTORMS LATE TUESDAY AND WEDNESDAY. DRIER AIR IS EXPECTED TO FINALLY BUILD IN CHRISTMAS DAY AS HIGH PRESSURE MOVES ACROSS THE AREA. A COLD FRONT MAY IMPACT THE CAROLINAS LATE NEXT WEEKEND.
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&& .NEAR TERM /THROUGH MONDAY/...
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AS OF 626 PM SUNDAY...LIGHT ECHOES ABOUND IN RADAR RETURNS ACROSS THE AREA BUT LITTLE TO NO RAIN IS FALLING IN THE BUCKETS PRESENTLY AND FOR THE EARLY GOING AT LEAST...WILL NEED TO SCALE BACK POP VALUES IN STARTING OFF THE EVENING UPDATE PRODUCTS. WILL AWAIT 00Z DATA PACKAGE TO DETERMINE IF ADJUSTMENTS LATER TONIGHT WILL BE NEEDED TO THE LIKELY/CATEGORICAL PROBABILITIES OVERNIGHT. NO OTHER SIGNIFICANT CHANGES AS T/TD VALUES ARE HOLDING PRETTY WELL UNDER A SOLID CLOUD COVER AND NE-ENE WINDS. PORTIONS OF THE PREVIOUS DISCUSSION FOLLOWS. A SURFACE LOW EMERGING FROM THE GULF OF MEXICO THIS EVENING WILL ENSURE CLOUD COVER RETURNS. THE LOW WILL MOVE NORTHEAST...PASSING JUST OFF THE GA/SC COAST OVERNIGHT AND DRAGGING A STALLED FRONT CLOSE TO THE AREA. AHEAD OF THE LOW DEEP MOISTURE WILL OVERSPREAD THE CAROLINAS. FORECAST SOUNDINGS PEAK PRECIPITABLE WATER VALUES AROUND 1.25 INCH CLOSE TO MIDNIGHT WITH ONLY A SLIGHT DROP IN PWATS THROUGH THE END OF THE PERIOD. GOOD ISENTROPIC LIFT WITHIN THIS AREA OF DEEP MOISTURE WILL LEAD TO LIGHT RAIN...POSSIBLY WITH BRIEF PERIOD OF MODERATE RAIN...DEVELOPING THIS EVENING AND OVERNIGHT. LOOKING AT THE ISENTROPIC FIELDS THERE MAY BE 2 DISTINCT PERIODS OF LIGHT RAIN OVERNIGHT. THE FIRST AROUND 00Z WITH A SECOND ROUND OVERNIGHT AND A PERIOD OF DRIZZLE BETWEEN THEM. INCREASING CLOUD COVER AND APPROACH OF SURFACE LOW OVERNIGHT WILL HELP KEEP LOWS NEAR TO SLIGHTLY ABOVE CLIMO. TEMP CURVE WILL NOT BE A TYPICAL ONE WITH LOWS LIKELY OCCURRING BEFORE MIDNIGHT THEN HOLDING STEADY OR GRADUALLY INCREASING.
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&& .SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/... AS OF 300 PM SUNDAY...A WEAK WAVE OF LOW PRESSURE WILL BE MOVING UP THE COAST AND LIFTING N OF THE AREA MON MORNING. THIS SHOULD TAKE THE MEASURABLE RAINFALL WITH IT. OTHERWISE HIGH PRESSURE ACROSS THE CANADIAN MARITIMES IS EXPECTED TO WEDGE STRONGLY ACROSS THE CAROLINAS. A VERY PRONOUNCED SUBSIDENCE INVERSION WILL TRAP LOW LEVEL MOISTURE IN PLACE LEADING TO A PROLONGED PERIOD OF WIDESPREAD STRATUS AND PATCHY DRIZZLE MON AND MON NIGHT. THERE MAY ALSO BE SOME FOG AROUND MON NIGHT. THE WEDGE IS EXPECTED TO HANG ON INTO TUE. A COASTAL TROUGH/WARM FRONT WILL STRUGGLE TO DISLODGE THE WEDGE LATER TUE AND TUE NIGHT. LOW PRESSURE IS EXPECTED TO MOVE OUT OF THE GULF OF MEXICO AND UP THROUGH THE TENNESSEE AND OHIO VALLEYS TUE NIGHT AND WED MORNING. THIS SHOULD FINALLY PROVIDE THE IMPETUS TO DRIVE THE WARM FRONT N OF THE AREA AHEAD OF A STRONG COLD FRONT WEST OF THE APPALACHIANS. WE MAY EXPERIENCE SOME SEA FOG ALONG THE COAST LATER TUE AND TUE NIGHT AS WARM AND MOIST AIR OVERSPREADS THE AREA. MODELS ARE PORTRAYING A HIGH SHEAR...LOW CAPE ENVIRONMENT DEVELOPING BEHIND THE WARM FRONT. WILL MAINTAIN MENTION OF THUNDERSTORMS TUE NIGHT AND THESE STORMS ARE EXPECTED TO REMAIN WITH US ON WED AHEAD OF A STRONG COLD FRONT. MIXED LAYER CAPE VALUES MAY ONLY REACH 500 J/KG...BUT 0-3 KM AGL BULK SHEAR VALUES REACH 40-45 KT TUE NIGHT AS LOW LEVEL SW WINDS INCREASE TO 40 TO 45 KT AND THEN SLIGHTLY HIGHER ON WED. THESE ARE INDICATIONS THAT SOME THUNDERSTORMS MAY BE AT LEAST STRONG LATE TUE NIGHT AND ON WED. WILL TREND POPS HIGHER TUE AND ESPECIALLY TUE NIGHT... REACHING 100 PERCENT. WIDESPREAD CLOUDS SHOULD KEEP TEMPS RATHER COOL WITH A RATHER FLAT TEMP CURVE. HIGHS ON MON WILL ONLY BE IN THE 40S WITH ANY LOWER 50S CONFINED TO THE COAST AND PERHAPS THE SOUTH SANTEE RIVER AREA. LOWS MON NIGHT WILL BE IN THE LOWER TO MID 40S. TEMPS TUE WILL BE TRICKY...IF THE WEDGE HOLDS STRONGLY ALL DAY...THEN HIGHS WOULD BE SIMILAR TO MON. HOWEVER...ANY SUBSTANTIAL EROSION AND TEMPS WOULD BE SIGNIFICANTLY HIGHER. THIS FORECAST PLAYS THE MIDDLE OF THE ROAD FOR NOW WITH HIGHS IN THE 50S...COOLEST ACROSS THE I-95 CORRIDOR AND WESTWARD. TUE NIGHT...LOWS SHOULD OCCUR IN THE EARLY EVE WITH TEMPS CLIMBING THROUGH THE LATE EVE AND OVERNIGHT HOURS. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... AS OF 300 PM SUNDAY...THERE WILL BE A WARM AND WET START TO THE LONG TERM PERIOD. A DEEP MID TO UPPER TROUGH EXTENDING FROM THE UPPER GREAT LAKES DOWN TO THE GULF COAST WILL PRODUCE A DEEP MOIST SOUTHERLY FLOW OUT AHEAD OF IT. THIS WILL STREAM UP THROUGH THE SOUTHEAST WITH AN INCREASING LOW LEVEL JET REACHING UP TO 50 KT BY THE AFTERNOON. THIS WILL ACT TO FUNNEL PLENTY OF MOISTURE AND WARM AIR INTO THE CAROLINAS AS SYSTEM MOVES EAST PUSHING A COLD FRONT INTO THE CAROLINAS BY WED EVE AND OFF SHORE BY THURS MORNING. PCP WATER VALUES REACH UP TO 2 INCHES ALONG THE COAST BY WED AFTERNOON AND TEMPS WILL REACH INTO THE 70S IN STRONG WAA. BETTER DYNAMICS ALOFT WILL AID IN POTENTIAL FOR STRONGER THUNDERSTORMS WITH GUSTY WINDS THROUGH WED AFTN. OVERALL EXPECT BEST CHC OF SHOWERS AND THUNDERSTORMS WITH HEAVIER RAIN AND GUSTY WINDS WED AFTN INTO THE EARLY EVE AHEAD OF COLD FRONT. MODELS SEEM A LITTLE SLOWER WITH COLD FRONT PASSAGE BUT EXPECT THE DIGGING MID TO UPPER TROUGH TO PUSH THE COLD FRONT THROUGH WED NIGHT BEFORE UPPER TROUGH FINALLY MOVES OFF SHORE BY THURS MORNING WITH DRIER AND COOLER WEATHER FOR CHRISTMAS DAY. EXPECT CLEARING SKIES THROUGH CHRISTMAS MORNING AND INCREASING SUNSHINE AND GUSTY WINDS THROUGH THE DAY. TEMPS WILL RUN A GOOD 10 DEGREES COOLER THAN THE DAY BEFORE. HIGH PRESSURE WILL BUILD UP FORM THE GULF COAST THROUGH LATE THURS INTO FRI. IT WILL REMAIN ELONGATED UP ALONG THE COAST AND THEN SLIP FARTHER OFF SHORE THROUGH FRI INTO SAT AT A COLD FRONT APPROACHES FROM THE W-NW. THE COOLER W-NW FLOW WILL SHIFT AROUND BY FRI TO W-SW AS COLD FRONT APPROACHES THE CAROLINAS FROM THE WEST. DO NOT EXPECT MUCH IN THE WAY OF MOISTURE RETURN AHEAD OF THIS FRONT AND FOR NOW WILL KEEP WITH A DRIER FROPA FOR SAT NIGHT. THE W-SW FLOW SHOULD HELP TO KICK TEMPS BACK UP ABOVE NORMAL FRI AND SAT. MODELS SHOWING QUITE DIFFERENT SOLUTIONS WHEN IT COMES TO THE WEEKEND. GFS SHOWS A DRY FRONTAL PASSAGE WITH DRY HIGH PRESSURE BUILDING IN BY SUNDAY. THE ECMWF SHOWS A WAVE OF LOW PRESSURE DEVELOPING ALONG THE FRONT ON SATURDAY WITH GREATER POTENTIAL FOR PCP THROUGH SAT INTO SUN AS THE LOW MOVES UP THROUGH THE SOUTHEAST AND FINALLY BRINGS FRONT THROUGH SUN EVENING. I WENT WITH A DRIER SOLUTION OVERALL BUT DID PUT SOME CLOUDS AND LOW END POPS IN THE FORECAST FOR THE WEEKEND. && .AVIATION /00Z MONDAY THROUGH FRIDAY/...
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AS OF 00Z...VFR CONDITIONS THIS EVENING WILL QUICKLY DETERIORATE OVERNIGHT AS LOW PRESSURE DEVELOPS ALONG AN OFFSHORE COASTAL TROUGH. CURRENT RADAR IMAGERY SHOWS SOME -RA/DZ MAINLY IMPACTING THE COASTAL TERMINALS ATTM...WITH SOME MVFR CIGS ALREADY BEING REPORTED. THE BEST LIFT FOR ADDITIONAL PRECIP WILL OCCUR AFTER MIDNIGHT AND INTO MON MORNING AS A SFC LOW MOVES UP THE COAST. KMYR/KCRE WILL LIKELY BE THE FIRST SITES TO SEE IFR CIGS DEVELOP...FOLLOWED SOON AFTER BY KILM AROUND 06Z. BY DAYBREAK...EXPECT WIDESPREAD IFR/LIFR CIGS AND -RA AT ALL TERMINALS. NORTHEAST WINDS AROUND 10 KT WILL CONTINUE THROUGH THE MORNING AS THE OFFSHORE LOW STRENGTHENS A BIT AND MOVES UP THE COAST. THE RAIN MAY TAPER OFF BY MIDDAY...BUT IFR CIGS WILL PERSIST THROUGH THE END OF THE PERIOD WITH COOL MOIST AIR LOCKED IN BELOW 1KFT. EXTENDED OUTLOOK...MVFR/IFR CIGS EARLY TUE MORNING WITH INCREASING CHANCES OF SHOWERS/TEMPO MVFR DURING THE DAY. EXPECT SHOWERS/MVFR AND GUSTY WINDS WED AHEAD OF A COLD FRONT. GUSTY WEST WINDS AND VFR THU BEHIND THE FRONT. VFR ON FRI.
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&& .MARINE...
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NEAR TERM /THROUGH TONIGHT/... AS OF 626 PM SUNDAY..SCA IN EFFECT AS GRADIENT WILL REMAIN PINCHED FOR MUCH OF THE PERIOD WITH HIGH BUILDING DOWN THE COAST AS SURFACE LOW MOVES NORTH. THE PINCHED GRADIENT WILL LIFT NORTH AND WEST AS THE LOW APPROACHES LATER TONIGHT...MOVING THE STRONGEST WINDS NORTH OF THE SC WATERS. AS A RESULT SCA WILL CONTINUE FOR NC WATERS THROUGH THE END OF THE PERIOD BUT FOR SC WATERS SCA WILL END BY MIDNIGHT. BUOY 41013 CONTINUES REPORTING 6 TO 7 FT SEAS AND ANTICIPATED PROLONGED NORTHEAST FLOW IN THE 15 TO 20 KT RANGE SHOULD PUSH SEAS OVER 6 FT INTO THE OUTER EDGES OF THE MARINE ZONES. THIS EVENT WILL BE ON THE MARGINAL SIDE WITH CONDITIONS NOWHERE NEAR SCA THRESHOLDS CLOSE TO THE COAST...ESPECIALLY IN AMZ252. SEAS WILL RANGE FROM 4 TO 6 FT WELL AWAY FROM SHORE AND IN WATERS EXPOSED TO EXTENDED NORTHEAST FETCH WHILE WATERS CLOSE TO SHORE AND SHELTERED FROM NORTHEAST FLOW WILL RUN 1 TO 3 FT. SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... AS OF 300 PM SUNDAY...WEAK WAVE OF LOW PRESSURE WILL BE LIFTING N ALONG THE COAST MONDAY. HIGH PRESSURE TO OUR NORTH WILL BUILD STRONGLY IN THE WAKE OF THIS WAVE. THIS WEDGE WILL BEGIN TO BREAK DOWN TUESDAY AS A COASTAL TROUGH BEGINS TO STRENGTHEN. THIS TROUGH/WARM FRONT WILL LIFT ACROSS THE WATERS LATE TUE AND TUE NIGHT. N TO NE WINDS MON AND MON NIGHT ARE EXPECTED TO VEER TO A MORE EASTERLY DIRECTION DURING TUE AND THEN TO SE LATE TUE AND TUE NIGHT. THE STRONGEST WINDS THIS PERIOD ARE EXPECTED TUE NIGHT...UP TO AROUND 20 KT. SEAS WILL BE NEAR 3 FT MOST OF THE PERIOD. THERE STILL MAY BE SOME 4 FT SEAS ACROSS PORTIONS OF THE WATERS MON MORNING. HOWEVER...SEAS WILL BUILD TUE NIGHT AND SHOULD EXCEED 6 FT OVERNIGHT. A SMALL CRAFT ADVISORY WILL BE LIKELY LATE TUE NIGHT AND BEYOND. AS WARMER AND MORE MOIST AIR WORKS ACROSS THE WATERS LATER TUE AND ESPECIALLY TUE NIGHT...THE RISK FOR SEA FOG AND STRATUS WILL INCREASE. POOR VISIBILITIES MAY DEVELOP ACROSS THE WATERS DURING THIS TIME. LONG TERM /WEDNESDAY THROUGH FRIDAY/... AS OF 300 PM SUNDAY...A LARGE AND POTENT STORM SYSTEM WILL PUSH A COLD FRONT EAST WITH INCREASING SOUTHERLY WINDS IN A TIGHTENING GRADIENT FLOW THROUGH WED. WINDS WILL BE UP TO 15 TO 25 KT AHEAD OF THE COLD FRONT. WNA CONTINUES TO SHOW SEAS RAMPING UP ABOVE 6 FT BY WED MORNING AND REACHING UP TO 7 TO 9 FT IN OUTER WATERS IN STRONGER SW TO W FLOW AS FRONT MOVES THROUGH THE WATERS LATE WED INTO WED NIGHT. EXPECT SMALL CRAFT CONDITIONS WED AND LASTING INTO THURS WITH HIGHEST SEAS GETTING PUSHED FARTHER OFF SHORE IN STRONGER W-NW FLOW BEHIND FRONT. THE WINDS WILL BECOME WESTERLY AFTER MIDNIGHT WED AND WILL DIMINISH AS THEY VEER AROUND TO THE NW TO N BECOMING 10 KTS OR LESS THROUGH THURS INTO FRI MORNING. EXPECT SEAS TO DROP BELOW SCA THRESHOLDS BY THURS AFTN ENDING UP AROUND 2 TO 4 FT BY THURS EVE AND DOWN FURTHER TO 3 FT OR LESS BY FRI MORNING AS HIGH PRESSURE MOVES OVER THE WATERS.
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&& .ILM WATCHES/WARNINGS/ADVISORIES...
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SC...NONE. NC...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 11 PM EST THIS EVENING FOR AMZ254- 256. SMALL CRAFT ADVISORY UNTIL 7 AM EST MONDAY FOR AMZ250-252.
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&& $$ SYNOPSIS...RJD/MJC NEAR TERM...III/MJC SHORT TERM...RJD LONG TERM...RGZ AVIATION...BJR

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