Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 141449 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 949 AM EST Sun Jan 14 2018 .SYNOPSIS... Cold and dry high pressure will build down the east coast through Monday. An area of low pressure may develop off the Carolina coast, and may bring a period of very light wintry precipitation Tuesday night into Wednesday. Arctic air will reach the area Wednesday and Thursday, bringing very low wind chill values. Temperatures will begin to rise Friday, and could surge above normal levels into next weekend. && .NEAR TERM /THROUGH TONIGHT/...
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As of 10 AM Sunday...Minimal changes required for the morning update. Arctic high over the OH Valley today will continue building over the region. Strong north to northeast flow and cold advection will offset abundant sunshine, keeping highs in the upper 30s to low 40s. Winds will be strongest in the morning, gradually weakening into the afternoon but gusts as high as 25 mph will be possible throughout the day.
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&& .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... As of 300 AM Sunday...Biggest challenge this period involves a potent vorticity impulse and shortwave which will impinge on the area Tuesday night. Have noted a distinct warming and drying trend in all available guidance, along with a slower progression of the upper feature. This suggests that precip will hold off until after 7am Tuesday, and be exclusively a Wednesday phenomenon. Although forecast soundings begin to show increasing saturation late Tuesday night within the dendritic growth zone coincident with increasing PVA ahead of the shortwave, very dry air remains beneath 700mb, likely indicating any snow will sublimate on its way down. This may help to saturate the column enough for some very light snow showers Wednesday, but will drop POP from this short term forecast except for the very far NW zones which may see some flurries before daybreak Wednesday. Additionally, guidance has also warmed for Tuesday night into Wednesday, likely in response to the slower trough progression allowing the strongest CAA to lag. Temps through the period are expected to remain below climo, with highs Monday only reaching the mid 40s, around 50 on Tuesday. Mins monday night will be chilly, low 20s across the area which is 10+ degrees below climo, but again, warm compared to the first week of January. Cloud cover and lagging CAA will keep mins Tuesday night from falling much below freezing. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... As of 300 AM Sunday...Minor changes to Wednesday to account for drier, warmer, and slower solution of all available 00z guidance. Have trimmed back POP both temporally and spatially, and added a R-/S- mix to the forecast. If trends continue, may end up dry through the period, but confidence not high enough for D4 to remove POP, and latest shifts will do a full analysis of the long term this aftn. Previous discussion outlining the potential for wintry precip below: As of 300 PM Saturday...Arctic air will briefly surge back across the area during the middle of next week and may bring some wintry precipitation and a brief period of dangerously cold wind chills. A deep longwave trough will dig across the eastern third of the nation Wed and then lift off to the NE and way from the Carolinas Wed night and Thu. The next disturbance will move out of the Four Corners region Wed, the Southern Plains Thu and the Gulf Coast states Fri, perhaps reaching the Southeast states Sat. The forecast becomes more unclear and the latest Euro is not consistent with its previous run in showing low pressure developing just off the Southeast Coast. Instead it now offers a solution a little closer to the GFS with weak areas of low pressure traversing a boundary well offshore with perhaps some consolidation near New England Tue night and Wed. Confidence is a little higher that vigorous shortwave energy will move across the eastern Carolinas and provide ample lift Wed before moving offshore Wed eve. We continue to include mainly chance POPs for Wed afternoon/eve, first starting across our inland most zones and ending lastly across the Cape Fear area. The column should be cold enough to support light frozen precipitation, at least for a portion of the time. We continue to advertise some light snow moving into NW zones Tue night and expanding across the entire area during Wed before ending Wed eve. The column will take some time to moisten and this looks like a low QPF event to begin with. Also, the column may not support frozen precipitation during the heart of Wed afternoon when the greatest coverage of precipitation may occur. Thus, from this vantage point, any accumulation of snow should be very light and perhaps just flurries. We will continue to monitor as models will eventually congeal on a plausible solution in regards to where and when coastal low development will occur. The peak of the cold air advection this period should keep highs closer to the upper 30s to around 40 Wed and Thu with some temp recovery likely on Fri and this trend will continue into the upcoming weekend. Lows will drop to the teens for most of the area Wed night. Wind chill values will be in the single numbers late Wed night and Thu morning. Perhaps not as cold Thu night, mainly 20s although a few teens will be possible. Lows Fri night should be in the upper 20s to mid 30s and temps Sat night should remain above freezing. && .AVIATION /15Z SUNDAY THROUGH THURSDAY/... As of 00Z...VFR this TAF valid period with SKC/scattered high clouds. Winds average N through the period, 10-20kt today subsiding to 7 kt or less for the overnight hours, Extended Outlook...Some potential for MVFR/IFR/wintry precipitation Wed, otherwise VFR. && .MARINE...
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NEAR TERM /THROUGH TONIGHT/... As of 10 AM Sunday...Pinched gradient and cold advection as Arctic high builds south will maintain northeast winds in excess of 20 kt over the waters today. This will keep seas over 6 ft into the evening, at which point the ongoing small craft advisory should be allowed to expire. Only minimal changes required for the morning update. SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... As of 300 AM Sunday...High pressure ridging down the coast will maintain its axis west of the waters through the short term. This creates persistent north winds, but they will be strongest through Monday at around 15 kts before easing to 5-10 kts Monday night into Tuesday. Winds may briefly become more westerly late Tuesday before veering back to the NW late as a cold front approaches. Highest seas will be Monday during the period of strongest northerly winds, reaching 3-5 ft through the evening, before falling slowly through the rest of the period. Seas will remain 2-4 ft even with very light winds however, thanks to a growing SE swell at 3-4ft/11 sec into early Wednesday. LONG TERM /WEDNESDAY THROUGH THURSDAY/... As of 300 PM Saturday...Small Craft Advisory conditions may develop Wed into Thu. Still unclear as to whether an area of low pressure will be able to close offshore of the Carolinas. Arctic high pressure will build across the waters late Wed night and especially on Thu. N winds at the start of the period should back to a W or SW direction Tue afternoon and night. The wind direction is expected to then veer to NW early Wed and to remain NW through the remainder of the period. Wind speeds will be highest Wed night into Thu, up to 20 to 25 kt. Seas will be 2 to 4 ft Wed, building to 4 to 6 ft during Wed and Wed night before subsiding to 2 to 4 ft later Thu.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...Small Craft Advisory until midnight EST tonight for AMZ250-252- 254-256. && $$ SYNOPSIS...JDW NEAR TERM...III SHORT TERM...JDW LONG TERM...RJD AVIATION...MRR

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