Area Forecast Discussion
Issued by NWS Wilmington, NC

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248 FXUS62 KILM 161631 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 1131 AM EST Thu Nov 16 2017 .SYNOPSIS... Seasonable temperatures today with cooler temperatures on Friday in the wake of a dry cold front. Canadian high pressure will move offshore Friday night and temperatures will warm above normal on Saturday, the first time that has happened in about a week. A few showers may accompany the passage of a strong cold front Saturday night. Much colder and drier air will be ushered in for Sunday and into early next week and we have a reasonable chance of a widespread freeze. Temperatures will moderate beginning Tuesday with dry weather expected next week. && .NEAR TERM /THROUGH TONIGHT/... As of 1100 AM Thursday...Temps warming nicely after a chilly start to the day as high pressure builds slowly down from the northwest. A decent westerly component to the flow this aftn, especially above the surface, will combine with bright Nov sunshine to warm temps well into the 60s most places this afternoon. By tonight, the mid to upper trough over New England will lift off to the northeast further pushing cold front farther off to the east, allowing a northerly surge of cool and dry Canadian air to move over the area. Dewpoint temps will be dropping overnight down into the low to mid 30s most places by daybreak Fri. At the same time, winds will remain up keeping boundary layer mixed through most of the night. This should prevent most places from radiating out, keeping temps a little higher than last night and therefore not expecting problems with frost this overnight. With that being said, any wind sheltered places could see some patchy frost but the surge of drier air and spikes in wind should prevent it in most areas. The best CAA will come after midnight with temps falling to 38 to 42 most places. The 850 temps up near 10c this aftn will fall close to 6c overnight. As Canadian high pressure to the north shifts east through Friday, winds will lighten and veer around to the N-NE. A cooler day overall on Friday with light northerly winds temps and temps reaching around 60 most places with plenty of sunshine. && .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... As of 300 AM Thursday...Deep and dry NW flow will be in place Fri with precipitable water values near one-quarter of an inch as Canadian high pressure moves overhead. High pressure will move offshore late Fri night and the low-level flow will turn SW. This SW flow will then increase through the day Sat ahead of a strong cold front which will serve to increase the moisture supply with precipitable water values exceeding an inch late Sat and Sat night. The brunt of the upper level support is expected to lift out across the central Appalachians and then across the mid-Atlantic. The primary lift across the eastern Carolinas will be in association with the surface front. This should keep the showers light and rainfall amounts small, generally a tenth of an inch or less. The POP strategy employed will thus favor the northern zones Sat night into early Sun, but still in the chance category at this point. It is interesting to note the magnitude of the low-level jet Sat night with 50 knots of wind showing up on model soundings about 1500 ft off the surface. Timing would strongly suggest virtually no instability, and model soundings support this as well. Still showers may be able to transport some higher winds to the surface Sat night. Current timing would sweep the cold front through during the early morning hours of Sun. Temps will be warming during this time, rising from highs around 60 Fri to lower 70s Sat. Sat will temporarily end the string of below normal days, that is until Sun and Mon when cold air advection will return with a vengeance. Likewise, lows will rise from the upper 30s to mid 40s from inland to the coast Fri night to upper 40s to mid 50s Sat night. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... As of 300 PM Wednesday...The passage of a strong cold front will usher in an airmass equally cold to the one we had back on November 11th which has the potential to bring freezing temperatures to portions of the eastern Carolinas Monday morning. After frontal cloudiness clears out during the day Sunday, insolation will be offset by cold advection and highs should only reach 60. We`re forecasting lows in the lower 30s as far south as Florence, Marion, Whiteville, and Burgaw Sunday Night as 850 mb temps plunge to around +1C. Up through Monday all the models were in great agreement with each other. Differences become apparent Monday night with regards to how quickly the incoming Canadian High moves across the Carolinas. The 00Z and 12Z ECMWF are both much faster moving the high across and offshore Monday night and Tuesday compared to the GFS. WPC prefers the ECMWF and its ensemble mean to the 06Z/12Z GFS, therefore I have altered our forecast with this in mind. A faster return flow behind the departing high pressure should make Monday night`s lows several degrees warmer than our previous forecast, and will lead to a faster return of clouds as Atlantic moisture increases Tuesday-Wednesday. && .AVIATION /15Z THURSDAY THROUGH MONDAY/... As of 12Z...One high pressure system will be replaced by another today. Look for northwesterly flow, peaking by late morning but still remaining mainly below 10 kts. Other than some passing cirrus, skies should remain cloud free. Winds will diminish this evening. Fog formation is a possibility and will examine more fully with the next model run. Extended Outlook...VFR with a chance of showers and possible MVFR/SHRA Saturday into Sunday. && .MARINE... NEAR TERM /THROUGH TONIGHT/... As of 1100 AM Thursday...High pressure building in from the northwest this morning will shift east through tonight. Weak gradient will maintain light offshore flow through the afternoon before winds slowly veer to northerly overnight. Cold surge will arrive mainly after midnight, increasing speeds from 10 to 15 kt this evening to the high end of the 15 to 20 kt range. Offshore flow will maintain 2 to 3 ft seas, with occasional 4 ft near 20 nm, into the afternoon and evening. Seas then start to build with the arrival of the cold surge and headlines may be needed late in the period as seas flirt with 5 or 6 ft. Will evaluate whether a SCEC or SCA will be needed by package update this aftn. SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... As of 300 AM Thursday...High pressure will be moving overhead Fri and then offshore Sat morning. A strong cold front will approach the waters late on Sat and then move across the waters near and just after daybreak Sun. The wind direction Fri will still be from the N and NE. The direction will veer to SE and S Fri night. SW winds will dominate Sat and Sat night, veering to W toward Sun morning. The highest winds this period will be late in the day Sat and especially Sat night, up to 20 to 25 kt. Wind speeds Fri will be decreasing from 15 to 20 kt early. Wind speeds late in the day Fri into Sat morning will be under 10 kt. Seas will be subsiding Fri with seas up to 4 to 5 ft Fri morning and possibly an isolated 6 ft reading across the outermost northern waters. Seas will bottom out in the 1 to 2 ft range overnight Fri and Sat morning before ramping up to 4 to 6 ft Sat night. LONG TERM /SUNDAY THROUGH MONDAY/... As of 300 PM Wednesday...Behind a strong cold front winds will shift to the N with cool Canadian air spreading across the area Sun. Small Craft Advisory conditions may be ongoing at the start of the period, with breezy, but lighter offshore winds continuing into Sunday night. Winds should veer northeasterly on Monday. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ NEAR TERM...III/RGZ SHORT TERM...RJD LONG TERM...TRA AVIATION...DL

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