Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 170140 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 840 PM EST Mon Jan 16 2017 .SYNOPSIS... High pressure will build over the area overnight. A stationary front over the southern mid-Atlantic states will move north as a warm front Tuesday. A weak cold front will push through the area early Wednesday. High pressure briefly returns Thursday followed by another system Friday. && .NEAR TERM /THROUGH TUESDAY/... In spite of ample low level cloudiness, surface high pressure resides from the Delmarva to the eastern North Carolina this evening. There have been a few sprinkles across northern Maryland and adjacent eastern West Virginia, but recent trends have been declining. Will reposition slight chance PoPs to chance sprinkles. In the bigger picture, overrunning and shortwave energy has been better across Pennsylvania. Low pressure can be analyzed near St Louis; the nearest organized rainfall is in the mid Ohio Valley. Recent RAP/HRRR runs suggest this area, supported by a warm front, won`t make it to the mountains til 12z...a little slower than GFS/ECMWF. The evening RAOB dry above 650 mb, so it will take some time for deep moisture to advance. Have scaled PoPs down for the overnight hours. Warm front and shortwave energy will lift northward toward the area into Tuesday...with overrunning precipitation overspreading the western zones early Tuesday. Rain chances increase rapidly during the morning, and peak near midday. Upper-level energy weakens as it approaches the area and it also skirts by to our north, so expect greater precipitation totals across NY and PA. Around here, generally less than a quarter of an inch, except in upslope areas across the Allegheny Front where a half inch (to locally three quarters of an inch) is possible. && .SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY/... While steadier rain ends by early evening Tuesday...scattered showers remain possible until weak cold front pushes through the area early Wednesday. Further...intense upper-level energy moves over the region Wednesday...which could lead to at least some isolated showers. Best chances for these would be across upslope areas and near the Mason Dixon line. Otherwise...expect warm weather with highs in the 50s to low 60s Wednesday. Drying out everywhere late Wednesday as high pressure builds into the area. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... High pressure over the region Thursday will slide to the East Coast Thursday night. Dry conditions are expected with mild temperatures. A low pressure system over the western Ohio Valley will pivot northeastward into the Lower Great Lakes region Friday into Friday night. Some energy associated with this main low will push across our region during the same time. Light to moderate rain will gradually spread northeastward across the Shenandoah Valley early Friday. Rain should reach the District of Columbia and surrounding areas by Friday afternoon. Temperatures will remain mild with high temperatures about 10 degrees above normal. Drier air will work its way into our region from the west behind this wave low pressure energy and escorted by high pressure building in from the Ohio Valley. Even though high pressure will be overhead Saturday into Saturday night, a weak piece of energy could linger nearby keeping clouds and perhaps a slight chance for rain showers in the forecast later Saturday into Saturday night. Temperatures will stay mild throughout the period. A separate area of high pressure over New England could aid in the cloud cover as we look at an onshore flow in the east and an upslope flow along the Blue Ridge and in the Potomac Highlands. High pressure will hang on Sunday and Sunday night as a low pressure system develops and deepens over the Mississippi Valley. This low could send additional energy into our region Sunday night, bringing the chance of rain showers once again. On Monday, the main low will try to pivot northeast, bringing a cold front across the region. The threat for more rain showers exist Monday with a continuation of mild temperatures. && .AVIATION /02Z TUESDAY THROUGH SATURDAY/... Trapped low level moisture have resulted in flight restrictions across the terminals. MVFR has dominated, although there have been periods of IFR, especially at CHO/MRB. Trends will be worsening as rain approaches, mainly during the overnight hours. By the morning push, anticipate widespread IFR, with LIFR possible. Restrictions will be due more to lowering ceilings vs vsbys, although vsbys will be affected by rainfall during the daylight morning/midday hours. Improving conditions anticipated late Tuesday into Wednesday as high pressure builds toward the area. VFR conditions Thursday and Thursday night. Winds northwest becoming south 5 knots Thursday. Winds south becoming southeast less than 5 knots. && .MARINE... Light winds expected through Tuesday. Wind gusts could approach marginal small craft criteria Wednesday afternoon behind the cold frontal passage. Winds subside late Wednesday as high pressure builds into the area. No marine hazards Thursday and Thursday night. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...None. && $$ SYNOPSIS...MSE NEAR TERM...HTS/MSE SHORT TERM...MSE LONG TERM...KLW AVIATION...HTS/MSE/KLW MARINE...MSE/KLW

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