Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 192049 AFDAKQ Area Forecast Discussion National Weather Service Wakefield VA 349 PM EST Thu Jan 19 2017 .SYNOPSIS... High pressure moves off the coast tonight. Low pressure tracks across the mid west 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 FRIDAY MORNING/... Sfc high over the fa late this afternoon will move offshore tonight. 12Z data continues to trend toward a dry night over most of the fa as the high is slow to retreat. Moisture ahead of a warm front approaches from the west late...mainly after 09Z. Expect increasing clouds tonight with some spotty light rain developing by sunrise across western most zones. Dry along and east of the I95 corridor. Lows in the mid 30s to lwr 40s. && .SHORT TERM /6 AM FRIDAY 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 /21Z THURSDAY THROUGH TUESDAY/... Sfc high pressure over the area will continue the VFR conditions through most of the 18Z forecast period. Expect the 3K FT BKN SC deck at SBY to dissipate by sunset. BKN CI will lower into a BKN AC deck by 12Z. Models don`t spread any pcpn east until after 14Z. Thus, only TAF site with pcpn will be RIC with MVFR cigs/vsbys in light rain/fog expected before 18Z. Outlook: IFR/MVFR conditions expected Friday afternoon as rain overspreads the etire area. The steady rain ends but expect areas of drizzle / fog Friday night into early Sat. Adverse aviation conditions expected into early next week as series of disturbances are expected to track across the area. && .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...MPR NEAR TERM...MPR SHORT TERM...MPR LONG TERM...SAM AVIATION...MPR MARINE...SAM

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