Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 150853 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 353 AM EST Fri Dec 15 2017 .SYNOPSIS...
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Low pressure will develop along the North Carolina coast this morning, moving northeastward and out to sea tonight. High pressure will return for Saturday before weak low pressure impacts the area early next week.
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&& .NEAR TERM /THROUGH TONIGHT/...
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An area of low pressure off the Carolina coast will move northeastward today, bringing light snow to the metro areas by this afternoon. As a result, a Winter Weather Advisory is in effect from 1pm this afternoon through 7pm this evening for Metro Baltimore and the District of Columbia, including the northern and eastern suburbs. Snowfall totals will be on the order of one to perhaps two inches across the advisory area, with the higher amounts expected to reside near the Baltimore area, and extending to the northeast. A sharp gradient will exists to the west of the metro areas, and exactly where this gradient falls will determine where the accumulating snow will cease. Temperatures throughout the day will hold at or slightly above the freezing mark, and with favorable atmospheric profiles, any precipitation that falls will be in the form of snow. Couple this with road temperatures expected to remain at or below freezing during the event, conditions could turn icy on untreated road surfaces. The snow will exit the area to the northeast by early Friday evening. Upslope snow showers are expected across the Allegheny Front Friday evening as northwest flow takes hold. Accumulations up to one inch will be possible in those favored locations. Temperatures overnight will drop down in to the middle to upper 20s as skies start to clear.
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&& .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
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High pressure builds in across the area on Saturday and Saturday night with dry conditions expected. Temperatures will top out during the day on Saturday in the upper 30s to middle 40s, with overnight lows in the 20s to near freezing in the metro area. High pressure will reside to our south on Sunday, resulting in southerly flow across the region. This will generate moderating temperatures in the mid to upper 40s. Conditions will remain dry during the day with high clouds beginning to stream overhead ahead of an approaching shortwave trough that will cross the region Sunday night and early Monday morning. There is a slight increase in precipitation as a result, but moisture looks limited and with marginal temperatures, most favored precipitation will be light rain showers across our northern zones. Lows overnight Sunday will bottom out in the mid to upper 30s.
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&& .LONG TERM /MONDAY THROUGH THURSDAY/...
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East coast 500 mb ridging will be the dominant feature for the extended forecast. Consequently, as shortwave energy traverses the CONUS Tuesday, the primary precip type will be rain. And, since the northern and southern streams will remain unphased, it`s looking like a lighter QPF amount for the DC/Baltimore metro. Will be carrying slight chance PoPs for most, chance for the mountains. High pressure and mild conditions will prevail for the balance of the week.
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&& .AVIATION /08Z FRIDAY THROUGH TUESDAY/...
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Predominate VFR conditions are expected through Sunday. A period of light snow is expected across our eastern terminals this afternoon and early Friday evening, which could result in periods of reductions to DCA/BWI/MTN. High pressure builds in to the area Saturday and Sunday with light to moderate westerly winds of 10 knots or less. VFR will likely prevail Mon-Tue. There will be an impulse moving through, so precip and flight restrictions will be possible, but confidence low.
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&& .MARINE...
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Low pressure passing to our east today and a cold front crossing the region will bring gusty winds Friday night into Saturday. As a result, SCA will go in to effect Friday night and will likely be extended into Saturday. Winds expected to remain below advisory criteria on Sunday. No hazards anticipated Monday into Tuesday. Winds will increase thereafter, but any flags may hold off til beyond current forecast period.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...Winter Weather Advisory from 1 PM this afternoon to 7 PM EST this evening for DCZ001. MD...Winter Weather Advisory from 1 PM this afternoon to 7 PM EST this evening for MDZ004>006-011-013-014-503>508. VA...Winter Weather Advisory from 1 PM this afternoon to 7 PM EST this evening for VAZ054. WV...None. MARINE...Small Craft Advisory from 9 PM this evening to 6 AM EST Saturday for ANZ530>533-538>541. Small Craft Advisory from 3 PM this afternoon to 6 AM EST Saturday for ANZ534-537-543.
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&& $$ SYNOPSIS...BKF NEAR TERM...BKF SHORT TERM...BKF LONG TERM...HTS AVIATION...BKF/HTS MARINE...BKF/HTS

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