Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 191859 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 259 PM EDT Sat May 19 2018 .SYNOPSIS...
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A slow moving warm front will move through the area tonight. A cold front will cross the area on Sunday and stall to the south on Monday before returning north on Tuesday.
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&& .NEAR TERM /THROUGH TONIGHT/...
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Front has been lifting north through southern MD today where new convection has fired up. New convection is also developing west of the Appalachians over northern WV and southwest PA. The area in southern MD should remain the most active through early this evening with the convection over WV and PA possibly approaching the Appalachian region mid evening. Southern MD remains the most vulnerable area to flash flooding because of all the rain that they had the past two days(6+ inches in some places in St. Marys county). Rest of the area, the threat of new or additional flooding has greatly diminished, so will be cancelling the flood watch for a large part of the fct area except for areas south of the Capital Beltway and King George VA. Showers will tend to dissipate after midnight.
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&& .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
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Should definitely see clouds break tomorrow with some sunshine as winds turn from the southwest. Scattered afternoon/early evening showers and t-storms are anticipated as cdfnt from the OH valley crosses the area. Southern MD will be again the most vulnerable area for flash flooding due to saturated soils and is the area where models show the best moisture convergence. Faster cell motion and mid-level winds nearly perpendicular to sfc front should keep cells moving and minimize flash flooding threat. The front will be returning north again on Monday with additional showers expected especially west of the Blue Ridge.
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&& .LONG TERM /TUESDAY THROUGH SATURDAY/...
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A chance of showers and thunderstorms will continue into Tuesday, with a front draped across our southern zones. Temperatures will be in the upper 70`s to low 80`s across the region, depending on the exact location of the front. A chance of showers and thunderstorms again on Wednesday, as a stronger low pressure system passes by to our north. A little more agreement in the latest guidance as far as frontal passage timing. The front should be through the area by Wednesday night. Temperatures will remain in the low 80`s. Nor a lot of precipitation expected during these two days, with maybe a quarter of an inch of additional precipitation. However, higher amounts are possible in areas that experience thunderstorms. High pressure builds into the area Thursday, and quickly slides off the east coast by Friday. Expect dry conditions during this period, along with seasonable temperatures.
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&& .AVIATION /19Z SATURDAY THROUGH THURSDAY/...
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LIFR/IFR conditions tonight improving rapidly to VFR after 14Z Sun as winds turn from the southwest. A chance of t-storm at all TAF sites Sun. Mainly VFR conditions forecast Tuesday and Wednesday, with the only threat of sub-VFR conditions being a passing shower over the terminals. Winds will be light and favor a southwesterly trajectory on Tuesday, turning Westerly on Wednesday.
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&& .MARINE...
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Winds will strengthen some tonight into Sun morning mainly over the southern waters and begin to diminish Sun afternoon. SCA conditions are expected tonight with SCA conditions possible again Tue afternoon into Wednesday. Generally sub-SCA conditions expected Tuesday and Wednesday, with winds remaining light. A frontal boundary will cross the waters on Wednesday, bringing the chance for some showers and thunderstorms. This could create periodic gusty winds on the waters.
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&& .TIDES/COASTAL FLOODING...
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Water levels are running around 1 to 2 ft above astronomical predictions on the Bay and lower tidal Potomac. Minor coastal flooding is possible at Annapolis and Straits Point tonight and Sunday. For the upper tidal Potomac around Washington DC and Alexandria, fresh water piling down from the Potomac River will cause anomalies to continue increasing tonight. This will affect Georgetown more than southwest DC or Alexandria. -For Alexandria: An advisory is in effect through 4 PM Sunday. -For Washington DC: Georgetown will be the driver due to the freshwater contribution, where moderate flooding is forecast for five cycles (with levels not dropping below minor through Sunday night). At the southwest waterfront, best confidence for moderate flooding will be near high tide tonight through Sunday; subsequent cycles may only be minor flooding. A Coastal Flood Warning is in effect for Washington DC through Sunday and it may need to be extended through Monday. A Coastal Flood Advisory is in effect for Alexandria through 4PM Sunday, and it may need to be extended through Monday as well.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...Coastal Flood Warning until 10 PM EDT Sunday for DCZ001. MD...Flood Watch until 8 PM EDT this evening for MDZ013-014-016>018. VA...Flood Watch until 8 PM EDT this evening for VAZ055>057. Coastal Flood Advisory until 4 PM EDT Sunday for VAZ054. WV...None. MARINE...Small Craft Advisory until 6 PM EDT Sunday for ANZ530>543.
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&& $$ SYNOPSIS...LFR NEAR TERM...LFR SHORT TERM...LFR LONG TERM...CJL AVIATION...LFR/CJL MARINE...LFR/CJL TIDES/COASTAL FLOODING...LFR

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