Area Forecast Discussion
Issued by NWS Sterling, VA

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292 FXUS61 KLWX 270858 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 458 AM EDT Mon Mar 27 2017 .SYNOPSIS... A warm front will positioned over southern Virginia will track north through the Mid Atlantic this morning. A cold front will cross the area late Tuesday. High pressure will build over the region Thursday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Given ground observations and traffic cams showing dense fog over the northeastwastern part of the forecast area a dense for advisory has been issued. It runs through 9 am. Overnight surface analysis shows low pressure centered over Michigan with a warm front extneding down the Appalachians into northern NC. The result for this forecast area is - overnight easterly winds, low clouds, fog, drizzle. The front is expected to progress northward through the Mid Atlantic this morning. Light rain will be possible as the front makes its move; afterwards warming is expected as the spring temperature roller coaster brings us back upward: yesterday only reached the upper 40s, it may take some time but expect this afternoon to reach the mid 70s over much of the region.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY/... While we will be forecasting "chance of showers" overnight believe for the most part the nighttime hours will be dry. If it does the best chances will probably be late ahead of the approaching short wave. Lows generally in the mid 50s. Tuesday could see thunderstorm activity as the shortwave tracks through the Mid Atlantic. SPC has placed much of the forecast area east of the mountains in a marginal risk of severe storms. Neither the CAPE or helicity look particularly impressive for us. Chances for precipitation should be ending Tuesday evening as the shortwave moves off the coast. High pressure will return overnight and for Wednesday. Back on the roller coaster... temperatures Wednesday should be almost ten degrees cooler than the previous two days. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... High pressure will be building into the Northeastern United States Wednesday night, sliding east on Thursday. This will lead to drier and cooler weather, although still near climatological normals. Good radiational cooling night Wednesday night will lead to widespread lows in the 30s, with highs rebounding back through the 50s on Thursday. Meanwhile, a strong closed low will be moving northeastward out of the southern plains on Thursday, into the Mid-Mississippi Valley Thursday night, and towards the Mid Atlantic states by later Friday, becoming vertically stacked and gradually weakening. Model guidance is in relatively good agreement with this progression and timing. As the system makes its way to the eastern seaboard, some redevelopment off of the Mid-Atlantic coastline Friday night into Saturday morning is also projected. Therefore, chances for rain showers increase Thursday night into Friday morning with initial warm air advection, followed by bulk of the rainfall likely coming Friday and Friday night with main frontal push and any subsequent redevelopment. A drying trend should develop on Saturday, with the chance for some lingering showers as the low pulls away. High pressure will then build in for Sunday. Temperatures in the Thursday night - Sunday time period will be relatively seasonal, skewing slightly above normal. Lows will be mainly in the 40s. Highs coolest on Friday in the 50s with clouds/showers, rising into the 60s for the weekend. && .AVIATION /09Z MONDAY THROUGH FRIDAY/... Very poor early morning conditions as the Mid Atlantic sits on the north side of a warm front. LIFR conditions will persist until at least sunrise. After that the level of improvement and the speed of it will be dependent upon the how fast the front pushes to the north as well as how much the sun can work on the low level moisture. This will need to be watched. But conditions are expected to reach VFR this afternoon. There will be chances of rain showers late tonight at all TAF sites..and then possible thunderstorms Tuesday afternoon. DCA has the best chance for strong gusty winds. VFR Tuesday night and Wednesday. VFR expected Wednesday night and Thursday, but chances for sub-VFR conditions increase Thursday night and Friday with rain and low clouds as next system moves into the area. Winds light Wednesday night into Thursday will increase out of the southeast later Thursday and Friday. && .MARINE... Winds have been below SCA levels so far overnight. Pushed the SCA back to after sunrise when the warm front is expected to make a rapid advance north through the waters. Thuderstorms will be possible Tuesday afternoon, some of which could produce SMW level winds. This will need to be monitored. Sub-SCA conditions expected Wednesday night and Thursday. Potential for SCA then increases Thursday night and Friday with increasing southeasterly winds ahead of an approaching system. && .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...Dense Fog Advisory until 9 AM EDT this morning for DCZ001. MD...Dense Fog Advisory until 9 AM EDT this morning for MDZ004>006- 011-013-014-016>018-503>508. VA...Dense Fog Advisory until 9 AM EDT this morning for VAZ038>040- 050>057-501-502-505-506. WV...None. MARINE...Small Craft Advisory from 9 AM this morning to 6 PM EDT this evening for ANZ533-534-537-541>543.
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