Area Forecast Discussion
Issued by NWS Sterling, VA

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547 FXUS61 KLWX 171955 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 255 PM EST Tue Jan 17 2017 .SYNOPSIS... A stationary front over the Carolinas will move north as a warm front this evening. A weak cold front will push through the area early Wednesday. High pressure returns Thursday followed by an approaching warm front Friday. High pressure returns again for Saturday. Low pressure will affect the area to start the new week. && .NEAR TERM /THROUGH TONIGHT/... Latest batch of organized steady light warm air advection showers continues to progress eastward across the area...with radar imagery showing the back edge just to the west of our office (Sterling, VA) as of 250 PM. In total...generally a tenth or two tenths of an inch of rainfall through this entire event...though up to a quarter of an inch along the Allegheny Front. Visible satellite imagery continues to show periodic clearing across the Shenandoah Valley...though, any clearing should be short-lived. Forcing will weaken by late afternoon, although spotty showers will still be possible until cold front passes through the area later tonight. Could also be some patchy fog around before cold front passes through near/around midnight...though increasing low-level wind field should mitigate this in most locations. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... Compact area of upper-level energy passes over the area tomorrow...with spotty light rain chances mainly across the Allegheny Front and along the Mason Dixon line. Elsewhere...expect drying/warming conditions as high pressure builds into the region through Thursday. Next system approaches late Thursday with showers approaching our SW zones by early Friday. Highs Wednesday and Thursday in the 50s. && .LONG TERM /FRIDAY THROUGH TUESDAY/... A storm 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. Weak high pressure will be overhead Saturday into Saturday night. Temperatures will stay mild throughout the period. A separate area of high pressure over New England could aid in some cloud cover with an upslope flow. A storm system will develop over the Mississippi Valley and deepen as it pivots northward Sunday and Sunday night. This low could send additional energy into our region Sunday into Sunday night, bringing the chance of rain showers once again. On Monday, the main low will move northward into the eastern Great Lakes. The threat for showers and perhaps a rumble of thunder exist Monday. Temperatures will remain mild. Drier air will push in behind the departing storm system Monday night. High pressure will usher in cooler and dry air on Tuesday. Clouds will breaking for sunshine, except for clouds and upslope rain and/or snow showers in the Potomac Highlands possible. && .AVIATION /20Z TUESDAY THROUGH SUNDAY/... at times LIFR...conditions continue over the next few hours as the last batch of rainfall moves across the terminals. MVFR (to locally IFR) conditions then possible until cold front crosses the region overnight. Mainly VFR tomorrow...though gusty NW winds up to 25 mph possible in the wake of cold front. Ifr to lifr conditions Friday with rain showers. Mvfr conditions Friday night. Winds southeast around 5 knots Friday. Winds light and variable Friday night. && .MARINE... Primarily southerly sub-SCA winds expected through tonight. However, with strong low-level wind field, may see some gusts approach SCA-criteria this evening and tonight. However, confidence is low. Winds will then turn to the northwest on Wednesday following cold frontal passage. Gusts up to about 20 knots expected...a Small Craft Advisory is in effect. Winds will then subside for Wednesday night through Thursday night. No marine hazards Friday through Friday night. Winds southeast becoming light and variable 5 to 10 knots Friday through Friday night. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory from 7 AM to 6 PM EST Wednesday for ANZ530>543. && $$ SYNOPSIS...MSE NEAR TERM...MSE SHORT TERM...MSE LONG TERM...LWX AVIATION...MSE/KLW MARINE...MSE/KLW is the U.S. government's official web portal to all federal, state and local government web resources and services.