Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 250806 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 405 AM EDT Sun Jun 25 2017 .SYNOPSIS... High pressure to the west will remain in overall control through Tuesday, but a series of weak cold fronts will be crossing the region during this time. The high will then cross the region Wednesday and settle over the western Atlantic Ocean late in the week. && .NEAR TERM /THROUGH TONIGHT/... One cold front sits off to our southeast at present while several more are located to our northwest. One of them will cross the region late today into this evening, but with little forcing aloft and limited moisture, no precip is expected. It will simply bring a reinforcing shot of cooler and drier air southward, with otherwise partly to mostly sunny skies prevailing today and remaining clear to partly cloudy tonight. Highs will be in the low to mid 80s with dew points in the 50s...quite nice for late June. Lows tonight will be mostly in the 50s except 60s in the cities and along the bay shore. && .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
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Another reinforcing shot of cooler air pushes south across the area late Monday into Monday night. Forcing remains weak and moisture remains limited so think precip will be hard to come by. Clouds may be a bit more common though. Highs will slip down a bit more with upper 70s to low 80s common. Dew points will slip into the upper 40s during part of the day. Lows Monday night will drop back into the 50s most spots, but still 60s in the warmest locales. Strong upper trough will cross the region Tuesday with another surface boundary. This trough is probably the most interesting weather through the forecast period, with increased instability associated with it. Some guidance is still dry with it (the Canadian suite), but others, including the NAM and ECMWF, are rather convective, so we could definitely see some scattered showers and thunderstorms given the cold pool aloft and decent PVA. For now have kept POPS rather low east of the mountains, but may need to be bumped if guidance comes into better agreement. Highs Tuesday will be quite cool, with most places failing to reach 80. Dew points will be slightly higher, with most places staying in the 50s. Clearing Tuesday night behind the trough, with lows into the 50s in most places, except near 60 in the cities and bay shore and 40s in the mountains.
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&& .LONG TERM /WEDNESDAY THROUGH SATURDAY/... The upper level trough axis shifts east of the Mid-Atlantic Tuesday night per global guidance consensus. The trailing surface low will then be overhead Wednesday before shifting offshore later that day. The streak of below normal temperatures end Thursday with the return southerly flow that begins Wednesday night. The high becomes centered over Bermuda with a return to summer- like conditions (max temps around 90F) Thursday into the weekend. The jet stream and associated low pressure looks to stay north of the central Mid-Atlantic/over the Great Lakes through the weekend with continued low chance probabilities for precipitation. && .AVIATION /08Z SUNDAY THROUGH THURSDAY/... VFR through the period with winds generally below 18 knots. Main concern will be an isolated shower or thunderstorm on Tuesday. Otherwise, no significant winds, precipitation, visibility or ceiling limitations expected. && .MARINE... Winds below SCA criteria currently, but with deeper mixing and another weak boundary passing through, expect some gusts to marginal SCA levels later today. Therefore have maintained SCA as inherited. Considered adding upper Tidal Potomac but confidence still not there for gusts this afternoon. It will be close, however. There is concern again for marginal SCA on Monday with another weak boundary and good mixing, but given marginal event expected, did not raise headlines yet. On Tuesday, a passing trough may cause spotty showers and thunderstorms, and given dry environment overall, some gusty winds could accompany them. Tranquil and cool weather Wednesday under surface high pressure. Return southerly flow begins Wednesday night as the high shifts to Bermuda. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory from 1 PM this afternoon to 10 PM EDT this evening for ANZ530>532-538>540. && $$ SYNOPSIS...RCM NEAR TERM...RCM SHORT TERM...RCM LONG TERM...BAJ AVIATION...BAJ/RCM MARINE...BAJ/RCM is the U.S. government's official web portal to all federal, state and local government web resources and services.