Area Forecast Discussion
Issued by NWS Sterling, VA

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297 FXUS61 KLWX 230758 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 358 AM EDT Sun Oct 23 2016 .SYNOPSIS... The mid-Atlantic region will be wedged between surface high pressure building over the southeast U.S. and deep low pressure over eastern Quebec today and tonight. Meanwhile, a clipper system will move across the Great Lakes region today, then continue east across southern Ontario tonight. The clipper`s cold front will cross the region early Monday, followed by cool high pressure for mid-week. A low pressure system will approach from the west late in the week. && .NEAR TERM /THROUGH TONIGHT/... At 300 AM, winds were still strong across the higher elevations and the warmer waters, with the strongest winds still at gale force over Tangier Sound. Temperatures were well mixed across the region, generally in the mid 40s to near 50 in the urban areas; however, several stations in sheltered valleys such as Stafford, Warrenton, and New Market have decoupled with temperatures in the mid 30s. Today will be another well-mixed windy day; although not as strong as yesterday, we will likely see gusts 30-40 mph during peak heating as the strong surface pressure gradient between the Quebec low and the southeast U.S. high continues. Max temps this afternoon will be in the mid 60s. Tonight, a clipper low will cross from the Great Lakes towards Ontario. Winds will be stronger at higher elevations as a local max H85 wind speed max crosses the region per the 00Z GFS. There will be some low level moisture advection that will increase dewpoints, so min temps will be from the low 40s at higher elevations and sheltered valleys to near 50 in the urban corridors to the Chesapeake. && .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... On Monday, the clipper`s cold front will cross the forecast area with additional cold air advection. This will keep temperatures seasonable Monday and Monday night, then about 5 degrees below normal for Tuesday and Tuesday night. Expect scattered upslope rain showers on Monday morning on strong northwest flow dragging moisture from the Great Lakes. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... A ridge of high pressure will extend from the eastern Great Lakes to the Mid Atlantic and Carolinas on Wednesday, providing mostly sunny skies albeit still a touch on the cool side. As the ridge axis slides east Wednesday night and Thursday, warm advection will increase aloft. Any thermal gains will be mitigated by increased cloud cover and potential showers from isentropic upglide. Guidance in better agreement than it was yesterday for the Thursday- Friday timeframe. The most likely scenario has a shortwave tracking east from the Great Lakes to the Northeast, dragging a surface cold front across the Mid Atlantic. Flow in the mid levels still remarkably amplified, the extent of which is still up for a little debate. This suggests there are timing details yet to be ironed out. Will maintain focus of POPs more on Thursday night; would not be outright surprised to see showers linger into Friday if these trends maintain some continuity. Will be in a west/northwest flow pattern on the back side of the trough late Friday into Saturday. Its still unclear, though, how much cold air will reside behind the front. && .AVIATION /08Z SUNDAY THROUGH THURSDAY/... Strong west/northwest winds for all terminals during the day both Sunday and Monday. No ceiling or visibility restrictions through the TAF period. VFR Wednesday under high pressure. Showers may approach Thursday ahead of a cold front. Periods of MVFR possible. && .MARINE... Needed to extend the Gale Warning until 4 AM as Crisfield was still gusting to 41KTS at 120 AM. Otherwise the Small Craft Advisories will continue through Monday, and possibly through Tuesday. However, the upper tidal Potomac may not reach criteria Sunday night and Monday night as some decoupling may be possible. Light winds under high pressure Wednesday. South flow will increase ahead of a cold front on Thursday. Small Craft Advisory conditions would be possible at that time. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory until 6 PM EDT Monday for ANZ530>534- 537>542. Small Craft Advisory until 6 PM EDT Monday for ANZ543. Gale Warning until 4 AM EDT early this morning for ANZ543. Small Craft Advisory until 6 PM EDT this evening for ANZ535- 536. Small Craft Advisory from 6 AM to 6 PM EDT Monday for ANZ535- 536. && $$ SYNOPSIS...Lee NEAR TERM...Lee SHORT TERM...Lee LONG TERM...HTS AVIATION...Lee/HTS MARINE...Lee/HTS is the U.S. government's official web portal to all federal, state and local government web resources and services.