Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 202323 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 623 PM EST Sat Jan 20 2018 .SYNOPSIS... Mild temperatures for January, will prevail through early next week. A cold front will bring showers Monday night into Tuesday morning. Temperatures will be near normal Wednesday and Thursday as high pressure builds in from the west. The high moves offshore for the end of the week with temperatures warming above normal. && .NEAR TERM /THROUGH SUNDAY/... As of 3 PM Saturday...A small eastward jog of surface high pressure through the period; the center of which goes from GA to overhead. And though looking at 850mb progs there does appear to be a weak sense of cool air advection forecast soundings show tomorrow should have deeper mixing. The end result is a milder afternoon with highs in the mid 60s area-wide. Lows tonight will be mainly limited by the increasing dewpoints, though the continuation of offshore flow may mean that models are too aggressive in their depiction of the moisture flux. && .SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/...
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As of 3 PM Saturday...Concern this period involves a cold front which will likely be along or just west of the coast Tuesday morning. Ahead of this feature, Sunday night through Monday evening, large high pressure offshore and gradually amplifying ridge aloft will drive WAA in a strengthening warm sector ahead of the aforementioned front. 850mb temps of around 7C early climb towards 10C late, and with abundant dry air persisting in the column at least through Monday eve, sunshine will be prevalent. This suggests temps climbing to well above normal, reaching near 70 Monday after lows Monday morning only around 40. The pattern begins to shift Monday night as a deep upper low cuts through the Great Lakes. Ahead of this feature, diffluence will increase and moist advection permeates into the Carolinas. Although the guidance differs slightly in timing, with the NAM being the fastest, the overall evolution is similar from each model. Although much of the forcing ejects NE away from the CWA, LLJ rises to above 50 kts with MLCape climbing to 200-400 J/kg, setting up the potential for an HSLC event into Tuesday morning. However, very dry air above 600mb appears to be limiting, and SHERBE values peak below 1 across the CWA. SPC does not even mention general thunder locally, but gusty winds and a brief period of heavy rainfall is possible late Monday night. Overall however, do not expect a high QPF or significant weather event with the FROPA. Cold advection lags well behind this boundary, in fact, it doesn`t occur until a secondary boundary crosses on Tuesday, so mins Monday night will be closer to typical seasonal highs, low 50s most locations.
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&& .LONG TERM /TUESDAY THROUGH SATURDAY/... As of 3 PM Saturday...Cold front in the area as the period begins is quickly lifted east-northeast as 5h trough, associated with Great Lakes 5h low, moves northeast. The bulk of the dynamics and moisture with this system end up passing to the north, limiting local precip chances the first half of Tue. This setup also helps keep the bulk of the cold air north of the area. Secondary cold front arrives Wednesday night, but even this feature lacks strong cold advection. Mid-level pattern in the wake of the exiting trough is relatively flat into the end of the week, helping quickly move surface high west to east. Late next week 5h ridge starts to build over the Southeast as 5h trough digs over the western CONUS. This will lead to an increase in deep moisture return very late in the period, but at this point confidence is very low and not quite ready to carry any mentionable pop. Temperatures above climo early in the period will dip near climo midweek following the passage of the secondary cold front. Temperatures bounce back above climo Fri and Sat as surface high off the coast and deep southerly flow begins a period of warm advection. && .AVIATION /23Z SATURDAY THROUGH THURSDAY/...
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As of 00Z...VFR this 24 hour TAF valid period. High pressure will move over the terminals by morning. TAFs indicate variable winds aob 5 kt the entire period. Wind directions most likely will be southeast Mon afternoon especially southern terminals. There will be an increase in mid and upper level moisture by morning. Densest clouds/cigs should remain south. Extended Outlook...VFR. Possible MVFR/SHRA late Mon/early Tue.
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&& .MARINE...
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NEAR TERM /THROUGH TONIGHT/... As of 3 PM Saturday...Offshore/westerly winds currently as high pressure sits to our west, approaching quite slowly. The center of the high transitions overhead Sunday. This will yield diminishing winds and seas and also some light and variable winds. Nearshore a seabreeze will develop but remain quite weak. SHORT TERM MARINE/SUNDAY NIGHT THROUGH MONDAY NIGHT/... As of 3 PM Saturday...Placid marine conditions Sunday night will ramp up quickly during Monday as a cold front approaches from the west, and an SCA is likely before the short term ends. High pressure over the area will push offshore Monday, leaving a weak gradient and light Southerly winds becoming SE and climbing to around 10 kts by late Monday. During this period, significant seas will be just 1-2 ft. Late Monday and especially Monday night, the gradient tightens and southerly winds increase rapidly to 20-25 kts, driving seas to 4-6 ft with a short southerly wind wave predominant in the spectrum. This will create short and steep waves, and likely necessitate an SCA that will persist into Tuesday. LONG TERM /TUESDAY THROUGH THURSDAY/... As of 3 PM Saturday...Cold front in the area at the start of the period will move east across the waters Tue morning. Winds will veer from south-southwest to west and then northwest later Tue and Tue night. Although cold advection is lacking, the gradient will keep speeds in the 15 to 20 kt range into Wed morning before starting to relax and allowing speeds to drop. Reinforcing shot of cooler air arrives late Wed night, as the surface high west of the area shifts east. Northerly flow increases as cool surge arrives and winds become northeast. Seas at the start of the period will probably warrant a continuation of SCA into the first half of Tue, but offshore flow is likely to knock seas under 6 ft by midday. Seas continue a steady diminishing trend Tue night and Wed, dropping to 2 ft on Wed before starting to build late Wed night as the cold surge arrives. Cold surge will push seas to a solid 3 ft with potential for isolated 4 ft as the period ends.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ NEAR TERM...MBB SHORT TERM...JDW LONG TERM...DCH/III AVIATION...MRR

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