Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 201739 AFDAKQ Area Forecast Discussion National Weather Service Wakefield VA 1239 PM EST Fri Jan 20 2017 .SYNOPSIS... High pressure pushes offshore today as low pressure tracks across the Midwest and into the Great Lakes region. The associated warm front lifts north into the area through tonight. A complex area of low pressure will affect the region early next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Adjusted pops/temps to better reflect current conditions this afternoon. pvs dscn: High res data indicating the band of mdt to lclly hvy rainfall across the piedmont weakens as it quickly moves east across the fa next svrl hrs with it pushing toward the coast after 18Z. Only sct pcpn expected behind this initial band of rain. Thus, minor changes made to crnt grids with the cat/likely pops next few hrs ramping down west to east as the day wears on. QPF one quarter to one half inch west of I95, a quarter inch or less east of there. Highs in the low/mid 50s most areas; upr 50s to near 60 NE NC.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY/... Any steady/lingering rain exits off the coast by late this aftn/early eveng. Otw, tsctns continue to show plenty of low level moisture across the fa tonight. Given a nearly saturated airmass and the warm front in the vicinity, maintained patchy fog/drizzle in the forecast. Lows 40 to 45. Saturday starts out with fog/drizzle then remains cloudy. Moisture from an approaching southern stream system progged a bit slower to move north so have kept PoPs no higher than 30-40% far southern areas, with silent PoPs near and NE of RIC. Rather mild despite the cloud coverage. Highs 55-60 near the water, 60-65 west of the bay. Models begin to diverge with the approaching system from the south Saturday night and especially Sunday. Initial low tracks NE along the spine of mts while secondary low pressure develops on an advancing frontal boundary from the south. Model differences lead to a low confidence temp forecast but high confidence PoP forecast. Yes it will rain, but uncertainties continue regarding whether pcpn will be entirely stratiform or if some convection can develop. Parameters are favorable for thunderstorms however, at least over southern areas, so maintained the chance of thunder in the forecast for Sunday. Also kept moderate pcpn rates in the grids, with locally heavy downpours possible as mentioned in the HWO. Highs mid-upr 50s north to mid 60s south, but temps could easily end up higher or lower, especially over southern areas. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... Upper level energy currently over the Gulf of Alaska is forecast to lift into the Mid-Atlantic region Sunday night. There are still some spatial and timing differences in handling of the associated surface low and frontal features in the 19/12Z guidance, but confidence is high that widespread precipitation continues Sunday night. POPs have been raised to categorical as upper level forcing and moisture are plentiful. The surface low is progged to lift along the Mid-Atlantic coast Monday as the upper low remains over the region. Best moisture flux and theta-e advection progged to be offshore, but have included a slight chance mention of thunder across the southeast local area Monday. Have trimmed daytime highs back a few degrees into the mid to upper 50`s. Upper/surface low pressure lifts northeastward away from the region Monday night and Tuesday, with precipitation chances winding down Tuesday afternoon. Upper/surface low pressure builds into the region Tuesday, sliding offshore Tuesday night as the next storm system approaches the region. Highs Tuesday generally in the mid 50`s under a partly cloudy to mostly cloudy sky. A cold front associated with an upper low lifting over the Great Lakes region progged to push across the region Wednesday into Wednesday evening. Moisture and forcing look rather meager at this point, so have kept silent POPs. Warmer Wednesday, with highs in the upper 50`s north to low 60`s south. Shortwave energy progged to push across the region Thursday, but a lack of moisture and westerly flow will result in ongoing silent POPs. Highs Thursday generally in the mid 50`s. Lows during the period will generally be in the 40`s, with the next chance for sub-freezing temperatures inland Thursday night. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
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Rain moving across the fa this afternoon ahead of an approaching warm front. Initially, the pcpn is falling out of a fairly high cloud deck (6-8K FT), but obs to the west showing IFR stratus overspreading the western piedmont as the second wave of pcpn tracks across the region. Thus. a TEMPO group was added over the next 2-4 HRS given the changable conditions. Latest data continues to show abundant low level moisture tonight along with areas of fog/drizzle. This will likely result in widespread IFR (with local LIFR) conditions from this evening right on though abt 15Z Sat. Expect a slow improvement toward the end of the forecast period. OUTLOOK...Ceilings and visbilities will deteriorate again Saturday night and Sunday morning with IFR possible at each of the TAF sites. Periods of widespread rain are expected Sunday through Monday as a strong low pressure system moves from the southern Great Plains and across Virginia Monday to off the New jersey coast Tuesday. This will result in unfavorable conditions for aviators. The weather improves by Tuesday.
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&& .MARINE... Winds generally se aob 10kt today as high pressure moves offshore this morning and a warm front lifts nwd through the region. Long period swell will allow 3-4ft seas to persist through today. Winds become more n-ne tonight as a weak coastal trough develops just off the Mid Atlantic coast...becoming more se Sat aftn into Sat night with speeds remaining around 10kt or less. Seas subside to 2-3ft tonight through Sat night. Waves 1-2ft. Onshore winds ahead of a strong area of low pressure Sun will increase to 15-25kt late Sun aftn/early evening through Monday. A period of low end gales is possible...especially across the nrn coastal waters during this time. The combination of onshore winds and a very tight pressure gradient due to the low rapidly intensifying (causing potential pressure falls of 4-8mb) will push seas to 5-6ft south/7-10ft north late Sun and upwards of 6-8ft south/8-12ft north on Mon. Waves generally 3-4ft (5ft mouth of Ches Bay). The sfc low tracks just ne of the Delmarva Peninsula by Tue morning. Although the airmass being pulled into the region on the back side of the low is not significantly cooler Tue than the previous conditions Mon night, the sfc pressure gradient will remain very tight with nw flow aloft, a shortwave passing overhead, and a decent 80-90kt jet nosing over the waters. In addition, pressure rises of 4-6mb will lend some credence to the overall instability and result in nw winds continuing around 15-25kt (gusts up to 30kt over the coastal waters) through Tue. Seas subside very slowly to an average of 4-7ft by late Tue aftn (possibly still 8ft near 20nm far nrn coastal waters) in the offshore/nw winds. Waves 3-4ft. High pressure and a warmer airmass advecting over the waters from the sw Tue night will act to stabilize conditions and allow winds to slowly subside overnight. Seas average 3-5ft/waves 1-2ft late Tue night. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...None. NC...None. VA...None. MARINE...None. && $$ SYNOPSIS...MAS NEAR TERM...MAS/MPR SHORT TERM...MAS/MPR LONG TERM...SAM AVIATION...MPR MARINE...BMD is the U.S. government's official web portal to all federal, state and local government web resources and services.