Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 180758 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 358 AM EDT Wed Apr 18 2018 .SYNOPSIS...
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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.
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&& .NEAR TERM /THROUGH TONIGHT/...
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Clearing skies have been observed across the region early this morning, with temperatures dropping in the upper 20s to lower 30s where winds have gone light. Along and east of the I-95 corridor, temperatures holding in the middle 30s to near 40 degrees for the warmer locations. A Freeze Warning remains in effect this morning until 9am for locations west of I-95, extending westward in to the eastern portions of the WV Panhandle, western MD, and the Shenandoah Valley. Clouds have been encroaching on the southwestern portions of our CWA as a developing warm front moves in. This will help keep some of these locations from falling to the freezing mark, so have elected not to extend the aforementioned Freeze Warning 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.
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&& .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
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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.
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&& .LONG TERM /SATURDAY THROUGH TUESDAY/...
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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.
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&& .AVIATION /07Z WEDNESDAY THROUGH SUNDAY/...
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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.
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&& .MARINE...
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SCA gusts will wane early this morning across most of our waters. Do expect occassional 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. Small Craft Advisories likely Thursday night and during the day on Friday as the low departs to the northeast and high pressure builds in from the west northwest. Pleasant boating conditions expected Sat into Mon with winds less than 10 kts under high pressure.
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&& .TIDES/COASTAL FLOODING...
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Possible minor coastal flooding at Washington Channel/DC Waterfront with high tide Wed morning due to mixed fresh and tidal input. Anomalies have been increasing recently and river level has also been increasing at Little Falls which makes coastal flooding more likely later today than yesterday.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...None. MD...Freeze Warning until 9 AM EDT this morning for MDZ003>006-011- 503>508. VA...Freeze Warning until 9 AM EDT this morning for VAZ026>031- 038>040-050>053-055-056-501-502-505>507. WV...Freeze Warning until 9 AM EDT this morning for WVZ051>053. MARINE...Small Craft Advisory until 6 AM EDT early this morning for ANZ530>534-537-539>543.
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&& $$ SYNOPSIS...LFR NEAR TERM...BKF SHORT TERM...BKF LONG TERM...LFR AVIATION...BKF/LFR MARINE...BKF/LFR TIDES/COASTAL FLOODING...LFR

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