Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 041203 AFDAKQ Area Forecast Discussion National Weather Service Wakefield VA 703 AM EST Sun Dec 4 2016 .SYNOPSIS... High pressure builds across the region through today. Low pressure passes south of the region late tonight into Monday. A complex area of low pressure crosses the region Tuesday. A strong cold front crosses the area Thursday. && .NEAR TERM /THROUGH TONIGHT/...
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Latest wx analysis features sfc high pressure centered over Southern Ontario and the interior Northeast Conus, with the sfc ridge nosing down into the Mid-Atlantic region. Aloft, closed upper low continues to dig south across NW Mexico, with numerous weak disturbances lifting ne toward the Gulf Coast and the Mid- South. Weak isentropic lift is ongoing from the Mid-South into the Western Carolinas, in the form of some spotty showers. High pressure slides east through the morning to a position along the Delmarva coast by mid-aftn. While this high keeps it dry in the lower levels, top down moistening process continues throughout the day. So while there could be some opaque sunshine early on this morning across the east, expect the day to average out cloudy/overcast to mostly cloudy. Isentropic lift increases by afternoon, with the HRRR and Hi-Res models are in fairly good agreement that light rain nudges into far SW corner of the CWA by mid to late afternoon. Sub-Cloud Layer remains quite dry owing to the sfc ridge, and thus only patchy light rain expected through sunset out west, and likely holding off until this evening into the overnight hours for most of the area. The clouds hold temps down with thickness tools in good agreement with cooler MAV numbers. Look for highs in the upr 40s for most to lwr 50s SE coast. First wave of energy from the low over the deep south ejects ENE along a developing trough over the Carolinas Sunday night. Models agree in quickly spreading moisture NE across the fa this evening. Best lift/support progged with southern wave over the SERN half of the area where greatest QPF will be (1/4" n to 1/2" s). Will carry chc e/likely pops piedmont during the evening then ramp up to likely pops most areas, and with categorical (80-90%) across SERN zones after midnight. light to moderate rain falling into In-situ wedge leads to a chilly rain with lows in the upr 30s- lwr 40s.
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&& .SHORT TERM /MONDAY THROUGH WEDNESDAY/... The sfc low pushes off the coast near Hatteras late Monday morning, with weak ridging building south across the area throughout the day in resultant subsidence behind the wave. Chc pops in the morning (except likely across extreme SE zones) quickly drop to slight chc Coastal NC zones in the afternoon, with a dry afternoon indicated elsewhere. Low levels remain moist enough to expect at least a partly/mostly cloudy sky through the day (i.e. more clouds than sun). Highs warm slightly into the low- mid 50s. Rain begins to push back in Monday night, as a second, stronger disturbance lifts NE through the lower Miss Valley from the opening main upper wave across the western Gulf Coast. Isentropic lift (290-300k sfcs) quickly ramps up again through the late evening and overnight hours. Forcing will be much better with this second wave, as large dry sub-cloud layer will not be as much of an issue at this point. PW quickly ramp up AOA 1" by 12z/TUE and 1.25-1.5 across the SE. Thus rain chances ramp up quickly to likely/categorical SW before midnight, with rain moving in over the rest of the area after 06z/1a. Lows in the mid- upper 40s. Tuesday`s forecast is another typical Mid-Atlantic system. Double barreled low pressure tracks NE along the mountains with a secondary low tracking NE along the coast. Copious amounts of both GOM/Atlantic moisture will fall into a strong wedge across the piedmont. Expect a wide temp range across the fa along with much needed/widespread rainfall. Challenge will be to define where the coastal low tracks as the NAM has an inland track with both the GFS/ECMWF tracking the low right along the coast. For now, will keep all pcpn stratiform with categorical pops. QPF through Tuesday night btwn 1/2 to 3/4 inches. Temps tricky but will continue with a sharp thermal gradient. Highs from mid-upper 40s across the wedged piedmont to near 60 across SE coastal zones. QPF through Tuesday night between 0.75"-1" north to 1.25-1.5" across the SE corner of the area. Low pulls away to begin the day Wednesday. Deep layered SW flow should allow for clearing and a warmer day. Highs mid to upper 50s. && .LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/... An upper low tracks across the Great Lakes Thursday and into southeast Canada Friday, as the upper trough digs into the eastern US. Medium range ensemble guidance and deterministic GFS and UKMET are in good agreement with pushing the associated cold front quickly across the region Thursday morning/Thursday afternoon. However, the ECMWF continues to be 6-12 hours slower, and much wetter, with the front. Forecast continues to track with the former solutions. Moisture return will be limited, with only slight chance to chance POPs generally over the northeast half of the forecast area Thursday. Highs Thursday in the low 50`s north to mid/upper 50`s south. As impressive dynamics/height falls and a strong surge of cold, arctic air reaches the local area Thursday night, cannot rule out light snow/flurries for the Maryland Eastern Shore. Lows drop into the upper teens to low 20`s inland to upper 20`s near the coast. Cool, breezy, and dry Friday as the latest GEFS indicates 850mb temperatures around -10 to -12C (-2 standard deviations). Highs are expected to warm only into the upper 30`s to low 40`s. Add in a breezy northwest wind and wind chills may only warm into the mid 30`s. Dewpoints in the upper single digits to teens will allow temperatures to drop into the 20`s (teens possible inland if trends continue) Friday night under a clear sky. 850Mb temperatures progged to moderate slightly Saturday (-6 to -8C) as cold high pressure centers over the region. Less mixing will result in another cool day, with highs back around 40 under a mostly sunny sky. High pressure forecast to slide offshore Saturday night as the next storm system approaches from the west. && .AVIATION /12Z SUNDAY THROUGH THURSDAY/...
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VFR conditions at all area terminals this morning, with VFR conditions to prevail through much of the upcoming period. High pressure slides out of the Ohio Valley and directly over the Mid Atlantic Region tonight into Mon. VFR conditions persist today as low pressure over the Gulf Coast slowly lifts northeast through Sunday night. Light rain currently over the Western Carolinas will spread east across SW VA/Central NC through midday today, pushing toward area terminals by sunset this evening. Ceilings will remain AOA 12kft through this period, before lowering as pcpn arrives through the night Sunday evening. MVFR ceilings expected, with brief LCL IFR possible at RIC after Midnight Sunday night and towards Monday morning at SBY, PHF, ORF, and ECG. Outlook: Rain (briefly) moves out early Monday, with VFR conditions returning. High clouds once again thicken and lower through the aftn on Mon ahead of next system. Steady rain to overspread the area from sw-ne late in the evening and overnight as shortwave energy streams into the area via the upper ridge which is also flattening overnight. High confidence of MVFR to IFR cigs/vis (and maybe even LIFR conditions) during this period. Rain continues through the day on Tuesday before tapering off Tue Night. widespread mvfr/IFR returns Tue night, with conditions recovering to VFR behind the system on Wed.
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&& .MARINE... Latest surface analysis centers high pressure just west of the waters this morning. The result is a diminishing north to northwest wind to around 10-15 knots. Waves 1-3 feet and seas 2-4 feet. High pressure settles over the waters today with flow veering from the northeast to south to southeast late today into this evening. Speeds generally at or below 10 knots. Waves and seas subside to 1-2 feet. High pressure slides offshore tonight as low pressure develops along the Southeast coast. Low pressure then lifts off the Mid-Atlantic coast Monday as high pressure builds in from the northwest. Flow becomes northwest Monday afternoon, increasing to 10-15 knots (up to 20 knots southern coastal waters). Winds then become onshore Monday night and Tuesday as high pressure centers over the Northeast and another area of low pressure lifts along the Southeast coast. SCA conditions are possible Tuesday afternoon as the gradient strengthens and speeds increase to 15 to 20 knots. Seas build to 4-5 feet late Tuesday with waves in the lower Bay building to 2-4 feet. SCA conditions possible into Tuesday night as low pressure lifts just offshore of the Mid-Atlantic coast. Flow becomes west-northwest 10-20 knots late Tuesday night, with seas still 4-6 feet. Sub-SCA conditions all waters Wednesday with a northwest wind 10-15 knots. A strong cold front Thursday will usher in the coldest and driest air mass of the season Thursday night through Friday night. Strong SCA (minimal Gale) conditions are possible. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...None. NC...None. VA...None. MARINE...None. && $$ SYNOPSIS...MAM NEAR TERM...MAM SHORT TERM...MPR/MAM LONG TERM...MAS/SAM AVIATION...MAM MARINE...SAM is the U.S. government's official web portal to all federal, state and local government web resources and services.