Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 151123 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 623 AM EST Mon Jan 15 2018 .SYNOPSIS... Cold and dry high pressure will hold into Tuesday. An area of low pressure will develop off the coast Wednesday, bringing a chance of rain or snow Wednesday. Arctic air will build into the area Wednesday night and Thursday. Temperatures will begin to climb again by Friday. && .NEAR TERM /THROUGH TONIGHT/... As of 300 AM Monday...Shortwave energy passing overhead by around 12Z will have no available moisture to produce much in the way of weather. This feature will swing the mid level flow to westerly or west-southwesterly while a large trough develops from the Great Lakes into the Mississippi/Ohio Valley region. At the surface a weakening ridge of high pressure holds on along the eastern seaboard, while a strong cold front impinges from the west. Cold advection is maintained through this evening in a weakening state, though the low level thermal trough moving offshore allows for some slightly higher BL and surface temperatures. Cold advection reversing briefly to weak warm advection late tonight for not quite the chilly readings of this morning yet lows still 10 degrees below climatology. The exception may be far western zones where predawn winds go calm under the axis of the weakening surface ridge. && .SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... As of 300 AM Monday...Despite our earnest wishes, winter is not done with us yet. A deep upper air trough will dig into the eastern U.S. for the middle portion of this week. Cirrus clouds ahead of the system will spread overhead Tuesday and thicken Tuesday night. By Wednesday morning a 140 knot jet at 250 mb will move across the Carolinas in advance of the trough. Model consensus is that low-level baroclinicity will remain too far east of the best vorticity advection for any significant deepening of the low that forms along the East Coast Wednesday. This means despite very impressive dynamics aloft, we will likely see no Atlantic moisture circulated back onshore like we did during the January 4th snow event. Tracing trajectories at 700 mb backwards, it appears what little moisture does move across the Carolinas is of Pacific origin routed across the northern Rockies and down through the Plains states. We see no compelling reason to raise PoPs for Wednesday which remain in the "chance" range, as high as 40 percent in the Bennettsville-Lumberton-Elizabethtown corridor. Using GFS/NAM thermal profiles as a guide, any precip that falls during the day Wednesday could be a rain/snow mix across the interior eastern Carolinas, with any shot at seeing snowflakes along the coast occurring after dark as drier and colder air chases the moisture offshore. QPF is expected to only be 0.05 inches at best, and our deterministic snowfall forecast is zero across the area. Our new probabilistic snowfall forecasts do show an inch of snow possible at the 90-95th percentile across portions of SE North Carolina. Very chilly air will race into the area Wednesday night on northwest winds that could gust to 25 mph during the evening. 850 mb temps plunging to -10C argue for a very chilly night, tempered only by the wind that will tend to keep low-level lapse rates steep. We`re forecasting upper teens inland to lower 20s at the coast, with wind chills falling to near 10 degrees overnight. && .LONG TERM /THURSDAY THROUGH SUNDAY/... As of 300 PM Sunday...Arctic high pressure will build strongly across the region Thu with its center passing to our S Fri and then offshore Sat and Sun. Southerly return flow will bring gradually higher temps and humidity levels during this time. A cold front will approach Sun night and may bring some showers, but otherwise it will be dry Thu through Sun. Highs will be around 40 Thu. High temps should rebound into the 50s Fri and Sat and 60s Sun. Some locations could again sneak down into the teens Thu night with strong radiational cooling. Lows will then trend from upper 20s and lower 30s Fri night to 40s by Sun night. && .AVIATION /12Z MONDAY THROUGH FRIDAY/...
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As of 12Z...MVFR clouds near KILM are scattered attm. Due to upper clouds moving across the terminals hard to judge the lower cloud trends. The upper trough is about to pass KILM in a few hours. Thus there will be a low chance of a MVFR cig at KILM until that passes. Otherwise VFR/scattered high clouds all terminals this TAF valid period. Winds will be NW-N 5-10 kt, becoming aob 4 kt after 23Z. Extended Outlook...Rain/MVFR/tempo IFR/with a chance for a wintry mix Wed, otherwise VFR.
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&& .MARINE... NEAR TERM /THROUGH TONIGHT/... As of 300 AM Monday...The pinched northerly gradient flow continues to relax albeit at quite a gradual pace. Seas down to 5ft at Frying Pan and still 4 ft at Masonboro Inlet buoy 41110 and so would feel more comfortable extending SCEC from 3am to 12Z. Georgetown County zone benefiting enough from wave shadowing to not require cautionary headlines. Predominant seas are a combination of 8 second NE swell and 5 second wind chop. This likely not changing late today and tonight, but overall significant wave height to drop by about a foot as the gradient eases from the approach of weak high pressure. SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... As of 300 AM Monday...A weak wave of low pressure will develop along a coastal trough out over the Gulf Stream off the Outer Banks Tuesday morning. Other than keeping a light northwesterly wind across our waters, little direct impact is expected on our weather. Attention will shift to a strong upper level system developing to our west Tuesday night into Wednesday. Several areas of low pressure developing across the Carolinas and Mid- Atlantic region will consolidate into a low off the New Jersey coast Wednesday morning. Offshore winds will increase substantially late Wednesday afternoon and continue through the night, likely necessitating Small Craft Advisories. In addition, there is a chance of some rain mixing with or changing over to snow before ending Wednesday night. LONG TERM /THURSDAY THROUGH FRIDAY/... As of 300 PM Sunday...Small Craft Advisory conditions likely to continue into Thu. Seas will peak in the 5 to 9 ft range Thu morning. Winds will decrease to 10 to 15 kt by Thu afternoon and then hold around 10 kt Thu night and Fri. The direction will back to NW during Thu, W Fri morning and to SW Fri afternoon. Seas will subside to 4 to 5 ft Thu afternoon with 2 to 4 ft seas generally expected Thu night and Fri. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ SYNOPSIS...TRA NEAR TERM...MBB SHORT TERM...TRA LONG TERM...RJD AVIATION...MRR

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