Area Forecast Discussion
Issued by NWS Wilmington, NC

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790 FXUS62 KILM 160757 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 257 AM EST Thu Nov 16 2017 .SYNOPSIS...
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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.
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&& .NEAR TERM /THROUGH TONIGHT/...
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As of 300 AM Thursday...Canadian High will build in from the northwest today and tonight. Zonal flow aloft quickly shifts the center of the high from the upper midwest at the start of the period to the OH valley by Fri morning. Skies should be mostly clear today and deep northwest flow will add a bit of a downslope component. Temps today could end up a good bit warmer than the last few days if partial thickness values are to be believed. Temperatures aloft are not a lot different from yesterday but the increased sunshine and the downslope flow will push highs into the upper 60s. A dry cold front will move across the are later in the day but the cold advection is delayed, not developing until closer to midnight. Once cold advection starts temps will fall with lows ending up in the mid 30s inland to around 40 along the coast.
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&& .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
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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.
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&& .LONG TERM /SUNDAY THROUGH WEDNESDAY/...
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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.
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&& .AVIATION /06Z THURSDAY THROUGH MONDAY/... As of 06Z...Mid-level cloud associated with a weak disturbance aloft will exit to the east around daybreak. High pressure building in from the northwest today with a dry cold front passing late in the day. Light northwest winds this afternoon will become northerly overnight and increase as cold surge arrives. VFR conditions will prevail through the TAF period. Extended Outlook...VFR with a chance of showers and possible MVFR/SHRA Saturday into Sunday. && 8 .MARINE...
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NEAR TERM /THROUGH TONIGHT/... As of 300 AM Thursday...High pressure building in from the northwest this morning will be quick to shift east later today and tonight. Weak gradient will maintain light offshore flow through the afternoon before winds slowly veer to northerly overnight. Cold surge will arrive during the late evening hours, increasing speeds from 10 to 15 kt 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. At this point unsure whether an SCEC or SCA will be needed so will hold off on any headlines. 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.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ NEAR TERM...III SHORT TERM...RJD LONG TERM...TRA AVIATION...III

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