Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 131956 AAA AFDLWX Area Forecast Discussion...UPDATED National Weather Service Baltimore MD/Washington DC 256 PM EST Fri Jan 13 2017 .SYNOPSIS...
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High pressure will build into the area through midnight tonight...as a complex frontal system develops across theTennessee Valley tonight. A warm front is forecast to push throughthe region Monday. A cold front will approach the area beforeweakening during midweek.
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&& .NEAR TERM /THROUGH SATURDAY/...
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High pressure will continue to build southward into the region through this evening drawing colder and drier air. At the same time, low pressure will develop over the TN valley and draw warm air aloft with precip developing over the central Shenandoah valley mainly after 9PM. Initially, sfc temps appear to be above freezing for plain rain. Wet-bulb cooling and strengthening cold air damming will bring temps below freezing overnight for western and northern areas with precip becoming of the winter variety. Model guidance are showing different p-type scenarios and duration times. How far south the sfc freezing line gets is questionable, but should be able to get as far south as Howard/Anne Arundel, Fairfax/Loudoun and Rapphannock/Culpeper county lines. We believe most of southern MD and the VA Piedmont will remain above freezing through early Sun. Given the uncertainty in thermal profiles and thus p-type, followed a more general wintry mix wording. For areas east of the Blue Ridge, this will be a light icing event with the potential for significant icing confined only to the higher elevations of the Blue Ridge and Appalachians. Temperatures will hold steady or begin a slow rise in the afternoon as precip becomes tapers off.
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&& .SHORT TERM /SATURDAY NIGHT/...
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Precip will become more spotty Sat night with temps slowly rising. There could be a few spots along the Mason-Dixon line that remain below freezing Sat night, but most areas will be above freezing.
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&& .LONG TERM /SUNDAY THROUGH FRIDAY/...
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High pressure will be centered to our northeast while a frontal boundary will be to our southwest. The boundary stalls while the high pressure moves to our east. Some guidance suggest that the boundary will be closer to our CWA, increasing PoPs over our region, while some other guidance keeps us dry. It is expected that the boundary will lift north as a warm front on Tuesday followed by a cold front on Wednesday. Guidance is again in disagreement with what will happen with the front. Some guidance stalls it to the south while other pushes it east and away from us, so one dryer scenario than the other. Temperatures will be near normal on Monday, followed by a warming trend Tuesday into Wednesday. We have to see what will happen with the Wednesday cold front.
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&& .AVIATION /20Z FRIDAY THROUGH WEDNESDAY/...
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Developing IFR/LIFR conditions overnight and Sat morning in wintry mix except at KCHO where just rain is expected. Frontal boundary near our region could bring some precipitation on Monday. Warm front lifts on Tuesday and cold front moves through on Wednesday. Therefore precipitation is still possible through Wednesday possibly bringing sub-VFR conditions.
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&& .MARINE...
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Winds still gusting to 20kt in some areas, but the trend is for diminishing winds through this evening. Winds become light and variable overnight through Sat night. Frontal boundary near our region could bring some precipitation on Monday. Warm front lifts on Tuesday and cold front moves through on Wednesday. Therefore precipitation is still possible through Wednesday, while winds are expected to stay below threshold.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...Winter Weather Advisory from midnight tonight to 6 PM EST Saturday for DCZ001. MD...Winter Weather Advisory from midnight tonight to 6 PM EST Saturday for MDZ003-004-013-501>504. Winter Weather Advisory from 4 AM to 6 PM EST Saturday for MDZ005-006-011-014-505>508. VA...Freezing Rain Advisory from midnight tonight to 6 PM EST Saturday for VAZ025-026-507-508. Winter Weather Advisory from midnight tonight to 6 PM EST Saturday for VAZ027>031-040-052>054-501-502-505-506. Freezing Rain Advisory from 10 PM this evening to 6 PM EST Saturday for VAZ503-504. WV...Winter Weather Advisory from midnight tonight to 6 PM EST Saturday for WVZ050>053-055-502>504. Freezing Rain Advisory from 10 PM this evening to 6 PM EST Saturday for WVZ501-505-506. MARINE...Small Craft Advisory until 6 PM EST this evening for ANZ530>532-535-536-538>541. Small Craft Advisory until 1 AM EST Saturday for ANZ533-534- 537-542-543.
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&& $$ SYNOPSIS...LFR NEAR TERM...LFR SHORT TERM...IMR LONG TERM...IMR AVIATION...IMR/LFR MARINE...IMR/LFR

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