Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 220222 AAA AFDLWX Area Forecast Discussion...UPDATED National Weather Service Baltimore MD/Washington DC 922 PM EST Tue Nov 21 2017 .SYNOPSIS...
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A cold front will pass through tonight into early Wednesday, while weak low pressure moves up the coast. High pressure will build back overhead later Wednesday through Thanksgiving Day. High pressure will be overhead Friday. A front approaches from the west on Saturday, High pressure builds later on Sunday and will remain in control through Tuesday.
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&& .NEAR TERM /THROUGH WEDNESDAY/...
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Light rain is expected to develop closer to midnight as forcing for ascent increases as weak low moves up the coast. Looking generally at a quarter inch or less south and east of I-95 with perhaps just a trace over the nw DC suburbs. A period of upslope snow showers are expected late tonight into Wed morning behind the cold front for locations along/west of the Allegheny Highlands. Accumulations should be half inch or less since moisture will be limited...but this may cause slippery conditions by the early morning hours Wednesday.
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&& .SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/... The cold front will move off to the south and east early Wednesday morning. Canadian high pressure will approach from the north and west and a northwest flow ahead of the high will usher in drier and chillier conditions. Max temps will hold in the 40s for most locations north and west of Interstate 95 and in the lower to middle 50s farther south and east. High pressure will build overhead Wednesday night...bringing dry and cold conditions. Min temps will drop into the 20s for most areas, except lower 30s downtown DC/Balt. High pressure will remain overhead Thanksgiving Day through Thanksgiving night...bringing more dry and chilly conditions. && .LONG TERM /FRIDAY THROUGH TUESDAY/... High pressure will be overhead Friday, keeping dry conditions over our region, before it moves offshore late on Friday. A front approaches from the west on Saturday, as upper trough deepens over the eastern CONUS. PoPs increases with this boundary on Saturday, but deterministic guidance and GEFS are not too aggressive with precipitation over our CWA. At the same time a low pressure system will develop off of the southeast Atlantic coast but it is expected to stay offshore with little to no impacts to our area. Upslope showers expected on Sunday with the northwest flow and upper trough axis moving through our area. Surface high pressure builds later on Sunday and will remain in control through Tuesday. && .AVIATION /02Z WEDNESDAY THROUGH SUNDAY/...
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A cold front will cross late tonight. A few showers cannot be ruled out (especially for DCA/BWI/MTN)...but any precipitation amounts will be light. MVFR conditions are expected late tonight into early Wed, most prolonged for DCA/BWI/MTN. Northwest winds will develop behind the cold front early Wednesday morning and gusts around 20 to 25 knots are expected for most of Wednesday behind the cold front. VFR conditions expected Wednesday into early Saturday. Precipitation possible later on Saturday as a cold front moves trough our area. Dry/VFR conditions return on Sunday.
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&& .MARINE...
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Winds will decrease overnight as the gradient relaxes. Will probably be cancelling SCA for tonight soon as winds have already diminished. A cold front will pass through early Wednesday morning and northwest winds will increase behind the boundary with gusts 25 to 30 knots most likely. An SCA is in effect for the waters. High pressure will build over the waters for Wednesday night through Thursday night. An SCA was extended through Wed night for most of the Bay and lower Potomac. Winds are expected to stay less than 20 kts Friday into Saturday night. Winds will increase on Sunday as low pressure moves NE offshore the Delmarva Peninsula, therefore, a small craft advisory is anticipated on Sunday.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...None. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory until midnight EST tonight for ANZ530>534- 537-539>543. Small Craft Advisory from 6 AM Wednesday to 6 AM EST Thursday for ANZ531>534-537-539>541-543. Small Craft Advisory from 6 AM to 6 PM EST Wednesday for ANZ530-535-536-538-542.
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&& $$ Update...LFR Products...CAS/FLING/IMR

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