Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 221423 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 1023 AM EDT TUE APR 22 2014 .SYNOPSIS...
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WARM TEMPERATURES ARE EXPECTED TODAY AHEAD OF A COLD FRONT THAT WILL MOVE THROUGH TONIGHT. HIGH PRESSURE WILL BUILD IN FROM THE NORTH WEDNESDAY...MOVING OFFSHORE THURSDAY. A BACKDOOR COLD FRONT MAY APPROACH FROM THE NORTH OVER THE WEEKEND.
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&& .NEAR TERM /THROUGH TONIGHT/...
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AS OF 1030 AM TUESDAY...A WEAK RIDGE OF HIGH PRESSURE AT THE SURFACE MOVED OFF THE COAST EARLY THIS MORNING. THE CAROLINAS ARE NOW IN A 500-MILE WIDE ZONE OF WEST-SOUTHWEST SURFACE WINDS BETWEEN THE OFFSHORE RIDGE AND A COLD FRONT NOW ACROSS MISSISSIPPI AND WESTERN TENNESSEE. THIS FRONT WILL MOVE EASTWARD AND ACROSS THE EASTERN CAROLINAS LATE THIS EVENING...PERHAPS ACCOMPANIED BY A BROKEN LINE OF SHOWERS AND THUNDERSTORMS. 12Z WEATHER BALLOON DATA SHOWS THE 06Z GFS SHOWED TOO MUCH MOISTURE BETWEEN THE SURFACE AND 700 MB ACROSS THE EASTERN CAROLINAS. THE 06Z NAM AND RUC WERE MUCH CLOSER TO THE OBSERVED VALUES ON THE CHS AND MHX SOUNDINGS. A BEAUTIFUL ARRAY OF SCATTERED HIGH ALTOCUMULUS CLOUDS ARE PRODUCING VIRGA FLURRIES OVER A LARGE SECTION OF THE COASTAL CAROLINAS THIS MORNING. VISIBLE SATELLITE SHOWS THESE SHOULD CONTINUE FOR THE NEXT FEW HOURS BEFORE MOVING OFF TO THE NORTHEAST. MODEL SOUNDINGS AND 12Z OBSERVED SOUNDINGS SHOW A THIN LAYER OF MOISTURE AROUND 16000 FT AGL RESPONSIBLE FOR THIS ACTIVITY. SEE OUR NWS ILM FACEBOOK OR TWITTER PAGE FOR A PICTURE. MODELS SHOW A POTENTIAL FOR SCATTERED SHOWERS AND THUNDERSTORMS AS THE FRONT APPROACHES THE EASTERN CAROLINAS LATE THIS AFTERNOON INTO THIS EVENING. MODEL CAPE INCREASES TO 400-700 J/KG WITH MOST OF THAT WAY UP IN THE 700-400 MB LAYER. THE LACK OF BOUNDARY LAYER MOISTURE...PRODUCED BY THE LACK OF ANY GULF OR ATLANTIC INFLOW... WILL PROBABLY BE THE LIMITING FACTOR REGARDING COVERAGE OF CONVECTION. A DEEP DRY MIXED LAYER THIS AFTERNOON REACHING 7000 FEET INLAND MEANS ANY CB CLOUD BASES ARE GOING TO BE WAY UP THERE...AND ANY EVAPORATING PRECIPITATION WITHIN THAT DRY SUBCLOUD LAYER COULD PRODUCE GUSTY WINDS. THIS IS PROBABLY AS CLOSE TO A CLASSIC WESTERN UNITED STATES PATTERN AS YOU`LL SEE IN THE CAROLINAS. BESIDES TWEAKING TIMING A LITTLE BASED ON THE LATEST SEVERAL HRRR RUNS...I HAVE MADE NO CHANGES TO THE PREVIOUS POP DISTRIBUTION FOR THIS EVENT: 30 POPS INLAND AND 20 AT THE COAST. HIGHS TODAY SHOULD REACH THE LOWER 80S AWAY FROM THE BEACHES. THE SEABREEZE WILL REMAIN PINNED TO THE SOUTH CAROLINA COAST AND SHOULD ONLY MAKE 15-20 MILES INLAND PROGRESS ACROSS SE NORTH CAROLINA GIVEN THE BACKGROUND WEST-SOUTHWEST WIND.
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&& .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... AS OF 300 AM TUESDAY...DEEP UPPER TROUGH AND SURFACE LOW OFF NEW ENGLAND COAST ON WEDNESDAY. CLOSER TO HOME WILL BE NEARLY ZONAL FLOW AND A WEAK PRESSURE GRADIENT. TEMPS A LITTLE BELOW CLIMO BEHIND TUESDAY NIGHT COOL FRONT BUT THE RAPID DRYING SHOULD BRING PLENTY OF SUNSHINE. THE CLEAR SKIES AND LIGHT WINDS WILL YIELD A PRETTY CHILLY WEDNESDAY NIGHT WITH LOWS CLOSE TO 10 DEGREES BELOW CLIMO. DESPITE SOME BUILDING HEIGHTS ALOFT HEADING INTO THURSDAY THE SURFACE HIGH PUSHES IN FROM THE N AND BRINGS A VERY WEAK SENSE OF CAA. HIGHS WILL AGAIN BE CAPPED A LITTLE BELOW CLIMO. AS THE RIDGE MOVES OFF THE COAST THURSDAY NIGHT A LIGHT SOUTHERLY FLOW DEVELOPS THAT SHOULD PRECLUDE AS COOL A NIGHT AS WEDNESDAY ALTHOUGH STILL BELOW CLIMO. && .LONG TERM /FRIDAY THROUGH MONDAY/... AS OF 300 AM TUESDAY...WARM WEATHER RETURNS ON FRIDAY AS DEVELOPING PIEDMONT TROUGH SERVES TO ENHANCE SOUTHERLY FLOW ALONG THE COASTAL PLAIN. IN THE STILL ZONAL MID LEVEL FLOW THERE WILL BE SOME WEAK DISTURBANCES THAT COULD TOUCH OFF ISOLATED CONVECTION. SATURDAY LOOKS WARM AS WELL WITH LIGHT SWRLY FLOW AND A BACKDOOR COLD FRONT APPROACHING FROM THE N. MODELS TEND TO KEEP THIS BOUNDARY JUST FAR ENOUGH TO THE NORTH TO PRECLUDE ANY REAL RAIN CHANCES LOCALLY BUT THEY DO INDICATE THAT ADDED CLOUD COVER AND SUPPRESSED HEIGHTS TEMPER THE WARMTH SUNDAY AND MONDAY. && .AVIATION /12Z TUESDAY THROUGH SATURDAY/... AS OF 12Z...VFR CONDITIONS ARE EXPECTED TO PREVAIL THROUGH THIS TAF PERIOD. INCREASING MID TO HIGH CLOUDS CAN BE SEEN ON SATELLITE IMAGERY THIS MORNING AHEAD OF AN APPROACHING COLD FRONT. LIGHT SOUTHWEST WINDS EARLY WILL STRENGTHEN TO 10-15 KTS THIS AFTERNOON. VFR CIGS WILL DEVELOP FROM WEST TO EAST LATER TODAY AS THE FRONT ENTERS THE CAROLINAS. HAVE MAINTAINED VCSH FOR ALL TERMS...BEGINNING WITH KFLO/KLBT BY MID-AFTERNOON...AS ISOLATED SHOWERS MAY DEVELOP AHEAD OF THE BOUNDARY. COVERAGE SHOULD BE LIMITED WITH THE BEST CHANCES FOR A BRIEF SHOWER AT THE INLAND TERMS. WINDS WILL VEER TO THE WEST THIS EVENING AND THEN NORTHWEST OVERNIGHT FOLLOWING FROPA. BY 06Z...THE FRONT SHOULD BE AT OR JUST THROUGH THE COASTAL TERMS AS MID LEVEL DRYING RESULTS IN MOSTLY CLEAR CONDITIONS THROUGH THE END OF THE PERIOD. EXTENDED OUTLOOK...VFR THROUGH THURSDAY. LOW CONFIDENCE FOR ISOLATED SHOWERS/TEMPO MVFR ON FRIDAY AND SATURDAY. && .MARINE...
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NEAR TERM /THROUGH TONIGHT/... AS OF 1030 AM TUESDAY...A WEAK RIDGE OF HIGH PRESSURE MOVED OFFSHORE EARLY THIS MORNING. FOR THE REMAINDER OF THE DAY WEST-SOUTHWEST WINDS WILL SLOWLY INCREASE IN ADVANCE OF A COLD FRONT NOW MOVING EAST ACROSS MISSISSIPPI AND TENNESSEE. THIS FRONT SHOULD REACH THE COASTAL WATERS AFTER MIDNIGHT TONIGHT...PERHAPS PRECEDED BY A BROKEN LINE OF SHOWERS AND THUNDERSTORMS. THE BEST WINDOW FOR SHOWERY WEATHER APPEARS TO BE FROM 9 PM UNTIL ABOUT 2 AM WEDNESDAY. OTHERWISE LOOK FOR A MODERATE SEABREEZE CIRCULATION TO DEVELOP ON TOP OF THE BACKGROUND WEST-SOUTHWEST 10-12 KNOT WIND...WITH SPEEDS NEAR THE BEACHES INCREASING TO SOUTH-SOUTHWEST 15-17 KNOTS DURING THE LATE AFTERNOON HOURS. SEAS CURRENTLY RANGE FROM 2.5 TO 4 FEET ACROSS THE COASTAL WATERS. A SMALL INCREASE IS POSSIBLE TONIGHT...ALTHOUGH IT APPEARS WE`LL SIMPLY BE TRADING A DECREASING LONG-PERIOD SWELL FOR AN INCREASED SHORT PERIOD WIND CHOP AS TIME GOES ON. SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... AS OF 300 AM TUESDAY...OFFSHORE/NWRLY FLOW WEDNESDAY FROM BOTH EXPANSIVE STORM OFF NEW ENGLAND COAST AND WEAK HIGH BUILDING INTO GREAT LAKES/OH VALLEY. AS RIDGE AXIS FROM THIS HIGH POKES INTO THE CAROLINAS FLOW WILL BECOME QUITE WEAK AND SEAS RAPIDLY DROP OFF TO JUST 2 FT. THE CENTER OF THE HIGH MOVES OFF THE COAST BY THURSDAY BUT REMAINS PROXIMAL ENOUGH FOR A CONTINUATION OF JUST 2 FT WAVES AS THE FLOW ACQUIRES A SOUTHERLY COMPONENT. LONG TERM /FRIDAY THROUGH SATURDAY/... AS OF 300 AM TUESDAY...SWRLY FLOW INITIALLY VERY LIGHT ON FRIDAY BUT A DEVELOPING PIEDMONT TROUGH WILL ACT TO TIGHTEN THE GRADIENT AND ADD PERHAPS A CATEGORY OR TWO OF WIND SPEED. EXPECTING NO HIGHER THAN A 15-20 KT FCST WHICH WILL BE SUFFICIENT FOR 2-4FT WAVES. THIS TROUGH MOVES OFF THE COAST AND WASHES OUT ON SATURDAY ONCE AGAIN RELAXING THE GRADIENT AND PERHAPS DROPPING A FOOT OFF THE HIGH END OF THE SIG WAVE FCST.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...NONE. && $$ SYNOPSIS...MBB/TRA NEAR TERM...TRA SHORT TERM...MBB LONG TERM...MBB AVIATION...BJR

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