Area Forecast Discussion
Issued by NWS Wakefield, VA

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050 FXUS61 KAKQ 200621 AFDAKQ Area Forecast Discussion National Weather Service Wakefield VA 121 AM EST Fri Jan 20 2017 .SYNOPSIS... High pressure moves off the coast tonight. Low pressure tracks across the Midwest and into the Great Lakes region Friday. The associated warm front lifts north across the area Friday night. A complex area of low pressure will affect the region early next week. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... Sfc hi pres sits near the immediate coast late this evening. SCT-BKN mainly high clouds continue to spread E and over the FA as lo pres tracks into the TN/OH valleys. Gradual increase in clouds expected overnight. Based on trends and near term guidance...will hold off on PoPs above 14% through 12Z/20. Lows in the l30s on the (Lower MD eastern shore) to around 40F far S. && .SHORT TERM /6 AM THIS MORNING THROUGH SUNDAY/... A wet day ahead Fri as a decent slug of overrunning moisture overspreads the entire FA during the morning hours ahead of the advancing warm front. Best lift progged across northern most zones for categorical pops, likely pops elsewhere. Best support for pcpn quickly exits to to the E-NE after 21Z so will show pops ramping down late across the west. QPF below one quarter inch. Highs in the 50s except near 60 ivof Albemarle sound. Any steady/lingering rain exits off the coast before midnight. Otw, tsctns show plenty of low level moisture across the fa Friday night. Given a nearly saturated airmass, added patchy fog/drizzle to the grids. Lows 40 to 45. Saturday starts out with fog/drizzle then remains cloudy. Moisture from the approaching southern system progged a bit slower to move north so have trimmed back pops a bit until after 20Z across the swrn most zones. 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 spine of mts while a secondary low pressure develops on a 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 will it be a stratiformed event like the GFS/ECMWF suggests as low pressure moves off the coast resulting in a insitu wedge scenario or more of a convective event like the NAM suggests as it has the warm front lifting north with abundant lift/moisture. Not getting fancy at this time, will slowly increase pops from chc to likely across the fa Saturday night with lows in the mid 40s to lwr 50s. Categorical pops (for shwrs) Sunday but limit any thunder chcs to southern most zones closer to where the boundary may end up being. Given the progged lift, theta-e advection/increasing PW`s, went ahead and indicated moderate pcpn rates in the grids. Locally heavy downpours will also be possible. Highs mid-upr 50s north to low to mid 60s south. && .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 /06Z FRIDAY THROUGH TUESDAY/... As of 06z...High pressure over coastal portions of the Mid Atlantic States will move off the coast early this morning. Low pressure will over the Mid Mississippi Valley will move northeast into Ohio. An upper level shortwave lifts northeast through the Mid Atlantic States today. Included some low vsbys that could last through mid morning for KECG where some fog has already developed in the vicinity. A broken layer of cirrus clouds over the area will increase with lower clouds moving in later this morning. Precipitation develops from the southwest this morning and spreads to the coast in the afternoon. MVFR conditions are expected with the precipitation. IFR ceilings are possible at RIC and SBY late in the day. Winds will be light through the period. OUTLOOK...IFR conditions are indicated for most of the area tonight into Saturday morning with fog and drizzle possible. Abundant low level moisture and weak surface flow will promote reduced aviation conditions through much of the day Saturday. 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. && .MARINE... Latest surface analysis centers ~1017mb high pressure over the Delmarva as low pressure deepens well offshore. Obs indicate light northeast to east winds over the waters, generally at or below 10 knots. Long period swell associated with the offshore system has resulted in seas of 3-4 feet. High pressure remains along the coast overnight with winds remaining at or below 10 knots. A few 5 footers are possible around 20nm out overnight. Sub-SCA conditions persist through Saturday night behind a warm front and high pressure offshore. Onshore flow ahead of a strong area of low pressure Sunday, will increase to 15-25 knots Sunday night through Monday. A period of low end gales is possible, especially across the northern coastal waters. Onshore flow will push seas to 5-6 feet late Sunday, and upwards of 7-10 feet into Monday. Waves 3-5 feet (6 feet mouth of the bay). Sub-SCA conditions return Tuesday (although seas will likely be slow to subside) as the low lifts northeastward, away from the area. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...None. NC...None. VA...None. MARINE...None. && $$ SYNOPSIS...ALB/MPR NEAR TERM...ALB SHORT TERM...MPR LONG TERM...SAM AVIATION...MAS/LSA MARINE...SAM

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