Area Forecast Discussion
Issued by NWS Sterling, VA

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615 FXUS61 KLWX 052001 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 301 PM EST Mon Dec 5 2016 .SYNOPSIS... High pressure will briefly build over the region today into tonight. Coastal low pressure will impact the area Tuesday into Tuesday night before high pressure briefly returns again for Wednesday. A potent cold front will pass through Thursday and arctic high pressure will build overhead during the weekend. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
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Mostly clear conditions will continue this afternoon and into tonight as high pressure approaches the region from the Ohio Valley. Light winds and clear skies will allow temperatures to drop into the 30s overnight ahead of the next low pressure system. High pressure will move over New England and filter down into the Mid- Atlantic by Tuesday morning. A negatively tilted shortwave trough will move into the gulf coast states overnight and warm airadvection will increase across the Mid-Atlantic overnight. Mid- highlevel clouds will increase from the Shenandoah Valley to northeastMD overnight and into Tuesday morning. As the surface low moves intothe TN Valley overnight/early Tuesday morning, precipitation willbegin to move into the VA highlands between after midnight tonight.As stated above temperatures will drop into the 30s overnight andnear freezing temperatures are expected at elevations above 2k feet.Due to the warm air advection aloft a warm layer will result inmixed precipitation at these higher elevations. A combination ofsnow and sleet are expected on the onset of precipitation. The warmlayer will continue and with temperatures below freezing...fzra isexpected through Tuesday at higher elevations. A winter weatheradvisory was issued for the Allegheny Front and VA Highlands.Elsewhere surface temperatures will be above freezing and the main p-type will be rain however a brief period of sleet is possible at theon-set.
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&& .SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY NIGHT/...
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Precipitation will spread northward into Tuesday morning and pockets of freezing rain are possible further east of the advisory mainly at higher elevations along the Blue Ridge Mtns and Catoctin Mtns. An extension to the winter weather advisory may be needed. Rain will move northward and into the DC metro and eventually to the Baltimore metro by late morning. Most of the forcing will be further south as low pressure moves off the Carolina coastline by Tuesday afternoon/evening. Rain amounts of around a half inch are expected through Tuesday however amts up to 0.75 are possible across Central VA/S MD. The shortwave trough will move across the region Tuesday night. Temperatures will likely max out in the 30s and around the low 40s across the I-95 corridor Tuesday afternoon/evening. Temps will slowly rise into the evening however winds will become NW by Wed morning and cool dry air will move into the region. Sunny conditions expected Wednesday with temperatures reaching the 40s and 50s along I-95. A cold front will approach the region
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&& .LONG TERM /THURSDAY THROUGH MONDAY/...
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A storm system will approach from the west Thursday and Thursday night. A chance of rain or snow showers exist across the region each period. Precipitation should be light in intensity with chilly temperatures. High pressure is expected to build in from the west Friday through Saturday night. This high could bring the chilliest air so far this season. Some upslope snow showers could also occur in the Potomac Highlands. The high will move offshore of the East Coast Sunday ahead of the next approaching trough of low pressure Sunday night into Monday. This next storm system could bring a chance of wintry precipitation at the onset Sunday night, change over to rain, before ending as a little snow sometime on Monday. The confidence in the timing and precipitation type is low. The 12z GFS model is moving this storm system eastward much faster than the 00z European model. We will have to see how the 12z European model handles the storm.
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&& .AVIATION /20Z MONDAY THROUGH SATURDAY/...
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VFR conditions are expected through this evening. Rain is expected to move into the terminals Tuesday morning. Cigs will lower and MVFR conditions are expected through Tuesday morning. A brief period of PL is possible mainly at CHO/MRB/IAD when rain moves into the region. Cigs will become IFR by Tuesday afternoon. Rain will move out of the region Tuesday evening however cigs will likely stay MVFR/IFR through Tuesday evening. VFR conditions expected Wednesday. Mvfr to ifr conditions possible in any rain or snow showers Thursday and Thursday night. Winds variable 5 to 10 knots Thursday becoming northwest and increasing 10 to 15 knots gusts 20 knots Thursday night.
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&& .MARINE...
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NW Winds will continue this afternoon as high pressure approaches from the west. A Small Craft Advisory is in effect for the waters during this time...but it will be marginal with gusts around 15 to 20 knots. High pressure will build overhead tonight before coastal low pressure impacts the waters Tuesday. A Small Craft Advisory is in effect for portions of the waters Tuesday afternoon. No marine hazards expected Thursday. Small craft advisories possible Thursday night. Winds becoming northwest 15 to 20 knots gusts 20 to 25 knots Thursday night.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...None. MD...Winter Weather Advisory from 2 AM to 7 PM EST Tuesday for MDZ501. VA...Winter Weather Advisory from 2 AM to 7 PM EST Tuesday for VAZ503-504. WV...Winter Weather Advisory from 2 AM to 7 PM EST Tuesday for WVZ501-503-505-506. MARINE...Small Craft Advisory until 5 PM EST this afternoon for ANZ530>543. Small Craft Advisory from noon to 6 PM EST Tuesday for ANZ532>534-537-540>543.
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&& $$ SYNOPSIS...HSK NEAR TERM...HSK SHORT TERM...HSK LONG TERM...KLW AVIATION...HSK/KLW MARINE...HSK/KLW

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