Area Forecast Discussion
Issued by NWS Sterling, VA

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104 FXUS61 KLWX 231816 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 216 PM EDT Sun Oct 23 2016 .SYNOPSIS... The mid-Atlantic region is wedged between surface high pressure building over the southeast U.S. and low pressure over Atlantic Canada. A clipper system will push through the northeastern U.S. Monday morning. High pressure will return for midweek. Low pressure will approach from the west late in the week. && .NEAR TERM /TONIGHT/... The autumnal cycle of cold fronts bringing temperatures down is underway. After a very warm week a front moved through Saturday which has brought temperatures back to more normal mid 60s values. Although this is expected to not produce any precipitation tonight the next system will be a fast moving short wave presently over the Upper Great Lakes. This will track into PA overnight and off the coast Monday morning. This will allow pressure gradient to tighten overnight. Winds will become gusty...especially at higher elevations...where gusts of 30 to 40 mph will likely overnight. Lows will be 50-55 with exception of cooler at higher elevations. && .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... High pressure builds into the Mid Atlantic Monday-Tuesday night. Exepct a comfortable day Monday with highs of 65-70. Monday night will see temps drop to the lower 40s...cooler at the higher elevations...warmer in the cities. Tuesday night high pressure will settle overhead providing excellent radiation conditions. Have added patchy frost along the M-D Line and west of the Blue Ridge as temps will likely fall into the mid 30s. Would not be surprised to see frost advisories issued with later releases. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... Guidance is in reasonable agreement through Thursday, but begins to diverge after that. At the beginning of the long term, we have a deep closed low over Atlantic Canada and a weak ridge extending from western Florida north to the Great Lakes, with a shortwave further west in the upper Mississippi Valley. By Thursday morning, all of these features shift east, with the closed low moving into the western Atlantic, the ridge axis just east of our region, and the shortwave over the Ohio Valley. By Friday, the first shortwave passes northeast and a second stronger one is crossing the area. By Saturday and Sunday, models diverge significantly, with solutions ranging from a closed low to fast moving shortwaves. In regards to sensible surface weather, high pressure will be off to the north on Wednesday, likely leading to radiational cooling and at least some areas of frost, if not perhaps a freeze in some spots. Wednesday will then features some increase in high clouds looking likely ahead of the next system. Clouds continue to thicken and lower Wednesday night as a front approaches, with showers possible in western areas late at night. This front then crosses the region late Thursday or Thursday night with a continued chance of showers. The front is east on Friday with high pressure trying to build back in, though guidance showing a closed low is slower. Another weak northern stream system may affect the area later in the weekend. Temp-wise, we will remain seasonable to a bit below normal through the long term as the Canadian influence and northern stream remain more dominant in our weather. && .AVIATION /18Z SUNDAY THROUGH FRIDAY/... VFR conditions expected tonight through Tuesday. VFR to start Wednesday, but sub-VFR cigs and vis possible Thursday as a frontal system moves through with rain. Improvements likely Friday. && .MARINE... SCA in effect for the Chesapeake Bay and lower Tidal Potomac through Monday. SCA comes down overnight for the upper Potomac but returns Monday. Sub-SCA likely Wednesday, then SCA possible Thursday and Friday with another frontal passage. && .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>543. 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. && $$ PRODUCTS...WOODY!/RCM is the U.S. government's official web portal to all federal, state and local government web resources and services.