Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 181410 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 1010 AM EDT Wed Apr 18 2018 .SYNOPSIS... Weak high pressure over the area will move offshore later today. Low pressure will move across the Ohio valley this afternoon and evening and into the Northeast on Thursday dragging a cold front through the area early on Thursday. High pressure will build in over the weekend and hold through the first half of next week. && .NEAR TERM /UNTIL 6 AM THURSDAY/... Clear to mostly clear skies are observed over most of our area, with some clouds lingering along the warm front towards the central Shenandoah Valley. Temperatures have risen between the upper 30s and the low to mid 40s at this time, therefore the Freeze Warning was canceled earlier this morning Temperatures will warm up appreciably today with the warm front off to the southwest and winds shifting southerly as high pressure slides off the southeastern U.S. coastline. Plentiful sunshine at least for the first half of the day will allow temperatures to warm nicely, topping out this afternoon in the lower to middle 60s for most, and upper 60s seem like a good bet along our southern zones. We will see clouds increase later this afternoon and into the evening as low pressure approaches from the west and the warm front continues its slow track northeastward into the area. Showers will develop overnight, sticking mostly to the Allegheny Highlands as low pressure passes just to our north. The ECMWF brings the track of the low a little further south than other global guidance, which would favor a bit more shower coverage east of the mountains. Will keep chance POPs north and west of the metro areas tonight, with likely POPs along the Allegheny Highlands. Temperatures tonight will be mild with ample cloud cover and a southwesterly flow aloft. Lows will generally bottom out in the 40s to near 50 in the city centers. && .SHORT TERM /6 AM THURSDAY THROUGH FRIDAY NIGHT/... As low pressure moves to our north Thursday morning, a cold front will drag across the area, turning winds gusty out of the northwest. Despite cold air advection kicking in around midday on Thursday, temperatures will still manage to near 60 in the metro areas, with lower to middle 50s to the north and west, with upper 30s to lower 40s along our far western zones. As cold air advection continues, the rain showers over the Alleghenies will transition to snow showers during the day. A coating to an inch or two of snow is feasible into Thursday evening. Canadian high pressure will build to our west northwest on Friday, with gusty northwest winds starting to subside by Friday evening. Mostly clear skies and dry conditions expected Friday and Friday night, with highs in the lower to middle 50s, and lows in the 30s. && .LONG TERM /SATURDAY THROUGH TUESDAY/... High pressure will be in control of the region over the weekend through the first half of next week and support dry conditions. Temperatures will be on the slow rise as heights rise, but still a little cooler than normal. Next chance of precipitation is not expected until at least Wed when a southern stream cutoff low approaches from the south, but timing remains highly uncertain. && .AVIATION /14Z WEDNESDAY THROUGH SUNDAY/... VFR conditions are forecast across all terminals today as high pressure traverses the area, keeping winds light and generally southerly at 10 knots or less. Clouds will increase late this afternoon and evening, with VFR CIGs, as low pressure approaches from the west and passes just north of the terminals through Thursday morning. Shower activity will be light and likely remain west of the terminals, with MRB seeing the best shot of brief MVFR conditions with this activity. Winds turn gusty out of the northwest by midday Thursday with a frontal passage, gusting upwards of 30 to 35 knots into Thursday evening. Gusty northwest winds will begin to subside during the day on Friday as high pressure dominates the terminals into the weekend, keeping winds northwesterly at 10 knots or less, and prevailing VFR conditions. No sig wx expected Sat or Sun. && .MARINE... Do expect occasional gusts to SCA criteria along portions of the upper Bay late morning and into the afternoon hours today, where a strong gradient will reside, thus have issued an SCA for these waters for this time period. Small Craft Advisories look likely across the lower Chesapeake Bay tonight, with Gale conditions expected for all waters during the day on Thursday as low pressure passes to the north and the gradient strengthens resulting in strong northwest winds. Gale Warning has been extended through Thursday night for the Chesapeake Bay, with the a Small Craft Advisory elsewhere as the low departs to the northeast and high pressure builds in from the west northwest. Small Craft may need to be extended into Friday. Pleasant boating conditions expected Sat into Mon with winds less than 10 kts under high pressure. && .FIRE WEATHER... Drier air advecting into the region Thursday on gusty west winds could result in an enhanced risk of fire spread Thursday, especially if fuel moistures decrease appreciably by then. && .TIDES/COASTAL FLOODING... DC southwest Waterfront hit minor flood this morning due to mixed fresh and tidal input. Minor flooding is possible through tonight. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...Coastal Flood Advisory until noon EDT today for DCZ001. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory until 5 PM EDT this afternoon for ANZ530>532-538>540. Gale Warning from 6 AM Thursday to 6 AM EDT Friday for ANZ530>534-538>541-543. Small Craft Advisory from 6 PM Thursday to 6 AM EDT Friday for ANZ535>537-542. Gale Warning from 6 AM to 6 PM EDT Thursday for ANZ535>537-542. Small Craft Advisory from 8 PM this evening to 6 AM EDT Thursday for ANZ534-543. && $$ SYNOPSIS...LFR NEAR TERM...IMR/BKF SHORT TERM...BKF LONG TERM...LFR AVIATION...BKF/LFR MARINE...IMR/BKF/LFR FIRE WEATHER...IMR/DHOF TIDES/COASTAL FLOODING...IMR/DHOF

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