Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 251940 AFDAKQ Area Forecast Discussion National Weather Service Wakefield VA 340 PM EDT Tue Apr 25 2017 .SYNOPSIS...
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Low pressure tracks northeast along the Mid Atlantic coast tonight, then slowly moves offshore Wednesday. High pressure builds into the area Thursday. A cold front stalls north of the region Friday.
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&& .NEAR TERM /TONIGHT/...
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Latest MSAS has the center of the filling low over the NC coastal plain and is progged to move NE tonight reaching a position off the eastern shore after 06Z. High res data combined with the latest radar trends would favor the highest pops along coastal sections this evening. Will carry likely pops there with chc pops elsewhere. Thunder chcs along an E of I95 through sunset then along the coast through midnight as the low drifts NE. Systm slow enough for moisture to linger through most of the night across the fa. Thus, kept chc pops after midnight. Concern then turns to the potential for fog development due to wet ground and warm temps. Will carry patchy fog in grids for now (except areas of fog ivof OXB, SPS currently in effect) and allow the evening shift to adjust the grids as needed. Lows 55-60.
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&& .SHORT TERM /WEDNESDAY MORNING THROUGH FRIDAY/...
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The low is progged to be east of Cape May NJ by 12Z Wed then slowly pulls NE away from the region as an upper level ridge builds in from the west. Thermal soundings cont to show some mid level moisture trapped beneath a strong subsidence inversion aloft, which will help keep clouds around most of the day across eastern zones. Even enough lingering moisture around for sct showers through 15Z or so along the eastern shore. Appears enough subsidence across the west for skies to become partly to mstly sunny after 18Z. Highs 75-80 west of the bay, upr 60s-lwr 70s along the coast. Mostly clr / pt cldy Wed nite. Lows in the upr 50s to lwr 60s. Ridge axis slides offshore ahead of an approaching cold front Thursday. Increasing return flow and 850mb temps around +14 to +16C (around +1 standard deviation) result in warm and dry conditions. Highs in the mid 80s west of the bay, upr 70s-lwr 80s eastern shore, cooler at the beaches. Models differ a bit in returning moisture across the mts Thurs nite. Appears a weak trof moves east producing low chc shwrs after 06Z. Lows in the 60s. Weak trof pushes east Fri morning. Will keep slght chc pops thru noon, then dry. Highs in the low to mid 80s except remaining in the 70s at the beaches.
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&& .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
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Temperatures are expected to remain well above normal through the weekend as an upper level ridge remains anchored over the Ern Conus. 850mb temperatures ~18C will support highs in the upper 80s to around 90 Saturday (75-80F at the immediate coast) after morning lows in the mid/upper 60s. A weak front will knock high temperatures down a few degrees Sunday over the Ern Shore, with low 80s expected and mid/upper 70s at the immediate coast. Meanwhile, highs W of the Bay will once again be into the upper 80s. Aftn/evening chances for showers/tstms Saturday/Sunday will be low and mainly aob 20%. A cold front approaches from the W Monday. Forecast highs Monday are in the low/mid 80s after morning lows in the mid/upper 60s. 25/12z GFS/ECMWF/CMC support the best chc for showers/tstms very late Monday aftn into Monday evening and shifting to the coast late Monday night. Temperatures trend back toward normal Tuesday with highs in the 70s.
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&& .AVIATION /20Z TUESDAY THROUGH SUNDAY/... Low pressure continues to move northeast across the region this afternoon before finally pushing offshore tonight. Widespread IFR ceilings continue over mainly northern portions of the area, including RIC and SBY, this afternoon. Closer to the center of low pressure over southeast portions of the region, some temporary clearing and mainly VFR ceilings are anticipated. Radar trends have shown diminishing coverage in rain showers this afternoon, but model guidance continues to hint at the redevelopment of showers across eastern portions of the area. Stratus and widespread IFR ceilings are expected to redevelop overnight as moisture wraps around the backside of the low pressure. Guidance has also been persistent with the development of patchy fog tonight and into tomorrow morning. Included MVFR visibilities for tonight, but it is possible IFR visibilities may develop in a few locations. Conditions will improve during the day on Wednesday, returning to VFR Wednesday afternoon. Light easterly flow is expected to continue through this afternoon and evening. Winds will shift to the W/NW as the low departs the area tonight and Wednesday. Winds remain light on Wednesday, generally 5-10 knots. Outlook: Aviation conditions improve through the day on Wednesday with VFR expected to return to the area. A shower or thunderstorm will be possible during the day on Friday, but otherwise, VFR and dry conditions should dominate the extended period. && .MARINE...
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Latest sfc analysis shows strong sfc low pres near the VA/NC coast. With the low directy over the area, winds have diminished this aftn to mainly sub-sca criteria. Waves and seas remain elevated however, with 4 ft waves expected to continue over the mouth of the Bay for another few hours and seas aoa 5 ft through daytime Wed for southern coastal wtrs and through Wed night for northern coastal wtrs. Also, a high surf advsry will remain in effect for the Lwr Eastern Shore beaches until early this eveng as nearshore waves remain ~8 ft. The sfc low pulls NE of the area late tonight into Wed with winds avgg aob 10 kt and seas slowly subsiding. Quieter marine conditions towards the end of the week with persistant S/SW flow over the area until early next week when the next cold front crosses the region.
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&& .TIDES/COASTAL FLOODING... Current tidal departures are averaging around 1.5 to 1.75 feet in the lower Bay and southern coastal waters due to ongoing onshore flow, while departures farther N are genly 1 ft or less. Have raised coastal flood advisories for zones adjacent to the lower Bay/James/York River, as well as the VA eastern shore. This will be for the upcoming high tide later this morning. More uncertainty exists farther N in the Bay up the coast and have continued with another round of statements for these areas for now. Surprisingly, despite continued onshore flow, currents data from Cape Henry Channel shows that water has been exiting the Bay at the same rate that it has been coming in/ i.e. piling of water into the Bay has been fairly minimal so far. ESTOFS and CBOFS data suggest this will change later today through tonight with the potential for water to become trapped in the Bay and for eventual minor flooding for the mid/upper Bay by tonight. May need to raise a coastal flood advisory later today for some of these locations, but did not do this yet because of how the winds associated with this system have genly underperformed so far. && .AKQ WATCHES/WARNINGS/ADVISORIES...
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MD...High Surf Advisory until 7 PM EDT this evening for MDZ025. NC...None. VA...High Surf Advisory until 7 PM EDT this evening for VAZ099-100. MARINE...Small Craft Advisory until 7 PM EDT this evening for ANZ634. Small Craft Advisory until 7 AM EDT Thursday for ANZ650-652- 654. Small Craft Advisory until 7 PM EDT Wednesday for ANZ656-658.
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&& $$ SYNOPSIS...MPR NEAR TERM...MPR SHORT TERM...MPR LONG TERM...AJZ AVIATION...AJB MARINE...MAS TIDES/COASTAL FLOODING...AKQ

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