Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 031507 AFDAKQ Area Forecast Discussion National Weather Service Wakefield VA 1007 AM EST Sat Dec 3 2016 .SYNOPSIS... High pressure slowly builds into the Mid Atlantic through Sunday. Low pressure passes south of the region Sunday night into Monday. Another low pressure system crosses the region Tuesday. && .NEAR TERM /THROUGH TONIGHT/...
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Current forecast on track with only minor adjustments made this morning. Adjusted sky grids a bit to account for the CI that is quickly spreading in from the west. Otw, mstly sunny with highs within a few degrees of 50. PVS DSCN: Latest wx analysis features 1028+mb sfc high pressure over the Mid-Mississippi River Valley into the western Ohio River Valley this morning. Aloft, main feature of note is amplifying upper low dropping from Southern California into Northwest Mexico. Downstream quasi-zonal flow is noted over the Mid-Atlantic and Southeast this morning as low amplitude upper ridging spreads east ahead of this system. This flow allowed some persistent mid to high clouds (mainly a thin CI deck) to spread from the Western Carolinas into southern sections of the local area earlier this morning. These clouds have thinned a bit further as depicted by NCAR ensembles and HI-res models agree in clearing sky out by around/just after sunrise, and have gone with this trend in the digital db. For today, continued mild and dry weather across the region w/sfc high pressure pushing east toward the local area under quasi-zonal flow aloft. Look for maxima to rise mainly in the low/mid 50s areawide under a mainly sunny sky. Clouds then increase through the night tonight into early Sun ahead of the low pressure system to the west. Low temps tonight mainly in the low/mid 30s and high temps Sun in the upr 40s to lwr 50s.
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&& .SHORT TERM /SUNDAY THROUGH TUESDAY NIGHT/... Pattern takes a turn towards a more active setup for the early to mid-week period of the week ahead. Rain chances will gradually increase later Sunday, and linger through much of the period. The first spoke of shortwave energy emanating from the southern stream trough will push northeast across the area late Sunday...as developing sfc low pressure takes shape over the Gulf Coast region. Look for top-down moistening to continue, with increasing clouds holding down highs by a few degrees tomorrow vice today`s highs, even as sfc high pressure lingers over the Mid- Atlantic Coast. Highs in the u40s to low 50s. By Sunday night, increasing isentropic lift will bring rain chances,first to the US-58 corridor, eventually spreading NE to Metro Richmond and the Lower Eastern Shore by near or just after midnight. QPF averaging around a quarter of an inch inland to near a half inch southeast, but even this moisture will serve to sharpen in-situ CAD wedge over the piedmont. Lows Sunday night not as cold with increasing clouds and pcpn moving in late...upper 30s to low 40s. Support for pcpn pushes east of the area Monday morning with weak ridging seen during the afternoon as sfc high pressure nudges offshore. Thus, maintained trend of lingering clouds and morning rain over coastal sections. Highs in the low-mid 50s. Tuesday appears to be the wettest of the period over the local area. Despite some differences, GFS/UKM/ECMWF all similar in their depiction of double barreled low pressure lifting toward the Mid- Atlantic Tuesday aftn and night.Rain looks to move in again from sw to ne on Tuesday morning through the aftn. Upshot here is that copious amounts of moisture will override the cooler air at the surface to allow a cool but mainly stratiform rainfall across the area from about 06Z Tues to 00Z Wed. Pcpn may become more convective across the SE but will all depend on the location of the front. Another lull seems to be favored Tuesday night as the system lifts toward the northeast. Did drop temperatures inland on Tuesday with the cool air wedge hanging tough inland as pcpn continues. Along the coast, forecast is a bit tougher, with models still struggling with location of the coastal front. Case in point...the Euro Ensembles varying by 5-7 std deviations for temperatures at most locations across the SE coast on Tuesday. Have sharpened the thermal gradient for highs, as is typical with entrenched CAD setup in place. Nudged highs up to around 60 along the coast, with highs only in the lower to middle 40s piedmont sections and l-m 50s i-95 corridor. && .LONG TERM /WEDNESDAY THROUGH FRIDAY/... Lingering trofiness keeps residual moisture across the area Wed with low chc pops east of I95 Wed. Seasonable with highs 55-60. Lows mid 30s to mid 40s. An anomalous upper level trough digs across the central US Thursday and into the eastern US Friday. A quick moving cold front progged to push across the region Thursday, ushering in the coldest air mass of the season. Numerical and statistical guidance still indicating a large spread of temperatures Thursday ahead of the front (depending on the frontal timing), so have opted to follow the lowering mean into the low to mid 50`s Thursday. Limited moisture return and westerly flow will limit precipitation chances Thursday and Thursday night, but will keep mention of slight chance POPs for the northwest Piedmont to the Maryland Eastern Shore. As impressive dynamics/height falls reach the local area Thursday night, might not be able to rule out some flurries across the northeast as strong cold air advection combines with lingering mid level moisture. Lows drop into the mid/upper 20`s inland to low 30`s near the coast. A cool/breezy/sunny/dry day forecast Friday as the latest GEFS indicates 850mb temperatures around -10 to -12C (-2 standard deviations). Highs are expected to warm only into the low 40`s (upper 30`s possible Piedmont). Add in a breezy northwest wind and wind chills may only warm into the 30`s. Dewpoints in the 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 warm to around -6 to -8 based on the latest ensemble guidance (still -1 standard deviation). Surface high pressure builds across the Southeast, resulting in less mixing and temperatures only warming to around 40. && .AVIATION /15Z SATURDAY THROUGH WEDNESDAY/... VFR conditions across area terminals early this morning should continue through the 12Z TAF period. High pressure builds in from the west through the weekend leading to continued dry weather. Some scattered mid to high clouds are possible across northern sections from RIC to SBY this afternoon, w/ any cloud bases generally to remain above 6000 feet. Winds will be gusty at times out of the northwest, and accounted for some gusts through the aftn at KSBY. Outlook: Clouds will begin to increase late tonight and into Sunday. The next chance for showers arrives Sunday night, with rain likely into Tuesday w/periodic Vis restrictions and MVFR conditions Tuesday afternoon and night. && .MARINE... Latest surface analysis centers ~990mb low pressure off the Canadian Maritime with ~1029mb high pressure over the Midwest. The result is a northwest wind of 15 to 25 knots over the local waters early this morning. Waves generally 2-4 feet and seas 3-5 feet. The pressure gradient relaxes over the lower Bay and southern coastal waters late morning/early afternoon as high pressure builds southeastward over the Carolinas. Northwest winds diminish to 10-20 knots in the southern waters this afternoon, but remain 15 to 25 knots in the northern waters. Have maintained SCA headlines for the southern waters through 1pm (seas subside to 3-4 feet), and have extended the northern waters through this evening. Seas in the northern waters 4- 5 feet. Sub-SCA conditions return to the waters late tonight as high pressure centers over the Mid-Atlantic region. High pressure centers over the waters Sunday with winds diminishing to at or below 10 knots. Waves 1-2 feet and seas 2 feet. High pressure slides offshore Sunday night and Monday, but a ridge remains over the waters as a coastal front aligns along the Southeast coast. Flow becomes southerly Sunday night, and then northwesterly late Monday and Monday night as high pressure builds over the Ohio Valley. Speeds remain at or below 15 knots. High pressure builds over the Northeast Tuesday as low pressure slowly lifts along the stalled Southeast coastal trough. Flow becomes onshore at 10-20 knots, with seas building to0 4-6 feet late Tuesday and Tuesday night. Waves build to 2-4 feet in the lower Bay. Low pressure lifts off the Mid-Atlantic coast Wednesday with northwest flow Wednesday night. A strong cold front Thursday will usher in the coldest and driest air mass of the season Thursday night through Friday night. Strong SCA (or even Gale) conditions are possible. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...None. NC...None. VA...None. MARINE...Small Craft Advisory until 1 PM EST this afternoon for ANZ632>634-654-656-658. Small Craft Advisory until 1 AM EST Sunday for ANZ630-631-650- 652. && $$ SYNOPSIS...MAM NEAR TERM...MPR/MAM SHORT TERM...MAM LONG TERM...MPR AVIATION...AJB/MAM MARINE...SAM

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