Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 071421 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 921 AM EST Thu Dec 7 2017 .SYNOPSIS... A cold and wet pattern will prevail into Saturday with lows in the 20s during the weekend. Another cold front by the middle of next week will reinforce the winter chill. && .NEAR TERM /THROUGH TONIGHT/...
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As of 920 AM Thursday...No substantial changes to thinking, latest guidance and trends still point to an extended period of cold and wet weather. The only changes to the gridded database/forecast have been to add 100% POPS for tonight and tomorrow in places where they were not already featured. Previous discussion from early this morning follows: A cold and dreary night persists across the area with widespread very light rain and drizzle falling into temperatures around 40 degrees. This precip is developing thanks to persistent isentropic lift in the 300K layer as SW flow aloft in response to a mid-level trough axis well to the west, tops cool surface northerly flow around a high pressure. This pattern will change little through tonight, so conditions are not expected to change drastically this period. Forecast profiles show subtle dry air advecting southward around high pressure through the first part of today. While this will do little to offset cloud cover or allow for any insolation/warming, do expect there to be a relative minimum in rainfall coverage after daybreak and through the aftn. The exception may be along the immediate coast where a better chance for showers exists due to better column moisture. However, total QPF through the day is expected to be light. The combination of cool north winds, overcast sky conditions, and periodic showers will keep temps abnormally cool today, and have undercut MOS numbers by several degrees. This leaves forecast highs only in the mid to upper 40s today, a solid 10+ degrees below normal for the date. Tonight, another shortwave is progged to eject through the base of the longwave trough and lift NE across the Carolinas. This enhanced forcing combined with continued isentropic lift will likely lead to another round of more widespread and heavier stratiform rain, and have pushed POP back to categorical tonight. The column becomes fully saturated and QPF could become robust, especially late overnight and into Friday. Temps through the column will be cool, but even the coolest guidance has most of the column slightly above freezing, so no p-type issues expected with just a cold rain forecast throughout. Mins tonight will fall only 5-10 degrees from aftn highs, with upper 30s forecast for most of the area, around 40 at the coast.
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&& .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... As of 333 AM Thursday...Primary headline this period is `Chilly and Wet` with maximum temperatures well below normal, even for early December. Not expecting frozen precipitation this period although a brief mix of wet snow with rain is not out of the question across northern sections of Robeson and Bladen Counties from Red Springs to White Oak, otherwise, it`s a very cold rain intermittently, that is on tap this period. Stratiform rain type is expected, with convection confined to the coastal waters and offshore. While rain will prevail off and on much of the period, two core rain periods are early Friday, and again late Friday into early Saturday, with 2-day rain totals across the area of 1.00-1.25 inches. Sharp 850mb drying will curtail rain coverage from NW to SE beginning Saturday afternoon, and by the time it gets cold enough to snow the moisture is swept away. Lows early Sunday by daybreak 27-32 most areas. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... As of 3 PM Wednesday...A deep eastern mid level trough will be in place through the period. There may be some light rain late in the period with the reinforcing shortwave but being seven days out confidence is not high. Of course with this type of pattern it will be blustery and cold with temperatures well below normal. Highs Saturday through Monday will be hard pressed to get out of the 40s with lows (augmented somewhat by a mixed boundary layer) in the 20s. Expect some moderation after this before the final shortwave drops in another chill. && .AVIATION /14Z THURSDAY THROUGH MONDAY/... As of 12Z...VFR mid-level cigs at the terminals this morning with intermittent light rain. Flight categories/cigs are not expected to change drastically through 00Z. The NAM model suggests MVFR or IFR cigs at times at the coastal terminals during the day, but confidence is low. Winds will remain N-NE aob 8 kts today coastal terminals with lighter speeds inland terminals. Winds could just be light and variable KFLO/KLBT by this afternoon. Model consensus/thus high confidence MVFR cigs will re-develop across the terminals this evening and lower to IFR/LIFR during the evening and overnight as rain increases ahead of an upper impulse. Extended Outlook...MVFR/IFR due to SHRA Friday, heaviest rainfalls coastal terminals. MVFR with showers ending Sat. VFR Sun/Mon. && .MARINE...
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NEAR TERM /THROUGH TONIGHT/... As of 920 AM Thursday...Latest obs show northerly winds from 10 to 20 kts over the waters with the lightest winds closest to the coast. Seas range from 2 ft near shore to 4 ft at the outer boundries of the forecast area. This is not quite yet meet exercise caution criteria for our headlines, but as the cold surge strengthens we still expect conditions to further deteriorate. Periods of cold rain are still likely to affect the waters today and tonight. Previous discussion from early this morning follows: Marginal SCEC conditions still expected to develop through the next 6-12 hours, despite conditions falling below criteria at the current time. Northerly winds will surge a bit through daybreak reaching 15-20 kts, and this will push seas to 3-5 ft, marginally dangerous enough that the ongoing SCEC will remain in place. By this aftn the winds will ease to 10-15 kts while continuing to feature a northerly direction and this allows wave heights to drop to 2-4 ft for a time, before ramping upward again late as winds re-energize overnight. Another cautionary statement may be needed tonight, but will hold off for now to eliminate any confusion of double headlines. SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... As of 333 AM Thursday...A difficult and unwelcoming marine period in which Advisories may be needed for N and NW wind gusts of 25 KT. Latest wavewatch 3 guidance showing 5 foot seas offshore Friday into Saturday, building to 6-7 feet late Saturday as cold high pressure surges across the waters. Wave spectrum forecasts show dominant wave periods of 5-6 seconds, making for steep and slightly hostile waves faces. Both Friday and Saturday will be hazardous for small craft and any noted improvements seen will only be temporary, offshore navigation is discouraged as TSTMS will occasionally troll the Gulf Stream. LONG TERM /SUNDAY THROUGH MONDAY/... As of 3 PM Wednesday...Sunday and Monday a strong northwest flow on the order of 15-20 knots will develop early on but diminish somewhat by late Monday. Some variability in seas as would be expected with the mostly offshore flow but expect 2-5 feet Sunday, dropping off Monday.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ SYNOPSIS...99 NEAR TERM...REK/JDW SHORT TERM...MJC LONG TERM...SHK AVIATION...MRR MARINE...MJC/REK/JDW/SHK

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