Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 151343 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 943 AM EDT Tue Aug 15 2017 .SYNOPSIS... A series of disturbances will move across the region throughout today bringing a chance of showers or an isolated thunderstorm. High pressure will build into the region tonight through Wednesday night. A cold front will approach from the west late in the week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Light to moderate rain will continue to move across the region the remainder of the today. There will be pockets of heavy rain moving across the Virginia Piedmont through Noon with a chance of a rumble of thunder in one or two places. A thunderstorm or two cannot be ruled out this afternoon as we have a few breaks in cloud cover and a disturbance moving along the area. Some clearing in the NW part of the forecast area in the latter stages of the afternoon. Given the cloud cover and fact that Monday was a rare day when the temperatures were cooler than guidance we`ll stay on the lower end of guidance. Highs generally around 80. && .SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY/... Tonight through Wednesday night area will be under the influence of high pressure. Lows tonight and Wednesday night in the upper 60s west of I-95, lower 70s east. Highs Wednesday around 90. Thursday morning should be dry. It appears that a warm front will approach the area during the day bringing a chance of showers and thunderstorms to the region during the aftenoon, although the models appear to be slowing down the approach of this system so PoPs may have to be pushed back with later forecast packages. && .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... Several chances for showers/thunderstorms exist for late this week and into the weekend, although no washout days are expected. We`ll likely be sitting in the warm sector of a frontal system Thursday night as the primary low pushes through the Great Lakes and into southern Canada. Thus a mild and muggy night is likely in store with lows in the low to mid 70s. A cold front will progress towards the region on Friday with humid and very warm to hot conditions out ahead of it. This will lead to the development of instability and therefore chances for scattered showers and thunderstorms. High temperatures should peak in the neighborhood of 90F. Uncertainty then exists as to how far south/east the front will make it before stalling out. Model guidance has trended less progressive over the past several cycles and 00z/0815 suites of both the ECMWF/GFS keep the frontal boundary near or over the region. This would allow for continued chances of isolated-scattered showers/thunderstorms, especially as an upper trough traverses overhead. That being said, run to run consistency is still low, so will keep PoPs slight to low chance. Temperatures/humidity values are also dependent on the frontal evolution, but have trended them up. By Monday, both model suites are in good agreement with high pressure building in. && .AVIATION /14Z TUESDAY THROUGH SATURDAY/... Clouds and light to moderate rain moving across the terminals this morning have brought VFR conditions down to IFR and LIFR briefly. We will see this reduction at times through the afternoon. Entire region will go back to VFR conditions this evening and remain that way into Thursday. Predominantly VFR is expected Thursday night through Saturday with potential for brief periods of reductions in isolated to scattered showers/thunderstorms, especially afternoon/evening. && .MARINE... Winds expected to remain below SCA values this afternoon through Thursday. South winds will be on the increase Thursday night and Friday ahead of a frontal system, and Small Craft Advisory conditions are possible. Sub-SCA conditions should then return by Saturday. Isolated to scattered showers and thunderstorms are also possible each day, mainly afternoon/evening. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...None. && $$ SYNOPSIS...KLW NEAR TERM...KLW SHORT TERM...KLW LONG TERM...MM AVIATION...MM/KLW MARINE...MM/KLW

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