Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 171850 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 250 PM EDT Tue Oct 17 2017 .SYNOPSIS... High pressure will remain across the Mid Atlantic through the rest of the week and this weekend. A low pressure system may affect the region early next week. && .NEAR TERM /THROUGH TONIGHT/...
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A sprawling area of high pressure will continue moving into the area this afternoon, cresting overhead late tonight and Wednesday morning. This will result in sunny skies and relatively light winds through the rest of the afternoon, with clear skies and calm winds overnight. This will provide for ideal radiational cooling conditions, with lows in the 30s for much of the area, except in the 40s in the immediate urban centers and along the shorelines of the Chesapeake and tidal Potomac. The growing season ended last night for western Allegheny, Mineral, Grant, Pendleton, and Highland counties, so no frost/freeze headlines there. Otherwise we have issued Freeze Warnings in the Shenandoah Valley for lows 30-32F, and Frost Advisories for much of the rest of the area, except the zones along the western shore of the Chesapeake Bay. The coldest readings will be in sheltered valleys away from large bodies of water and away from urban areas.
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&& .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
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Surface high pressure will remain in control Wednesday, although will gradually shift southward by Wednesday night as a weak system moves into New England Wednesday night into Thursday. We may see an increase in some high clouds Wednesday night into Thursday morning as the system passes by to the north, but otherwise no sensible impacts. High pressure will then expand back northward Thursday night. Temperatures will be moderating through the week, with highs Wednesday in the upper 60s to around 70F, and reaching the low to mid 70s on Thursday. Low temperatures will be a bit milder than tonight, generally from 35-45F Wednesday night and 40-50F Thursday night, with 50s in the urban centers and along the Chesapeake and tidal Potomac shorelines. There may be some areas of frost again Wednesday night given these temperatures, although not as widespread as tonight.
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&& .LONG TERM /FRIDAY THROUGH MONDAY/...
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High pressure system centered near or over our area will keep dry condition on Friday as it slowly moves offshore on Saturday. Condtions will continue to be dry on Sunday as it moves away from the coast. A cold front will approach from the west on Monday with a wave of low pressure tracking through it as an upper level trough amplifies over eastern CONUS. Guidance suggest precipitation associated with the cold front could start as early as Monday afternoon and last into Tuesday with periods of heavy rain at times. High temperatures will be between the low to mid 70s on Friday to the mid to upper 70s on Monday. High temperature decreases on Tuesday into the 60s.
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&& .AVIATION /19Z TUESDAY THROUGH SUNDAY/...
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High pressure will provide mostly clear skies and light winds through Sunday.
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&& .MARINE...
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High pressure will crest overhead tonight and remain nearby through Saturday, before moving offshore Sunday. A weak system will pass by to the north Thursday night. Winds will be 10 kt or less for much of the time, with the exception of Thursday night when gusts may approach Small Craft Advisory criteria.
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&& .TIDES/COASTAL FLOODING...
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Anomalies have begun to recover today as northwest winds have abated. While no flooding is currently forecast, the sensitive sites of Straits Point, Annapolis, and Washington DC may reach action stage and will need to be monitored.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...Frost Advisory from 1 AM to 9 AM EDT Wednesday for DCZ001. MD...Frost Advisory from 1 AM to 9 AM EDT Wednesday for MDZ003>006- 013-016-017-502>507. VA...Frost Advisory from 1 AM to 9 AM EDT Wednesday for VAZ028>031- 036>040-050>057-501-502-505-506. Freeze Warning from 1 AM to 9 AM EDT Wednesday for VAZ025>027. WV...Frost Advisory from 1 AM to 9 AM EDT Wednesday for WVZ050>053- 055. MARINE...None.
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&& $$ SYNOPSIS...MM NEAR TERM...MM SHORT TERM...MM LONG TERM...IMR AVIATION...MM/IMR MARINE...MM/IMR TIDES/COASTAL FLOODING...MM

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