Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 261835 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 235 PM EDT Wed Apr 26 2017 .SYNOPSIS...
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Low pressure east of New Jersey will slowly move away from the coast. A cold front will approach the region and weaken over the area Thursday night. A backdoor front may slide into the area late Saturday into Sunday. A cold front will pass through the region early next week.
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&& .NEAR TERM /TONIGHT/...
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The atmosphere over the Mid Atlantic is moving in slow motion courtesy of a vertically stacked low east of NJ. As discussed this morning clouds across northern VA/MD/DC have barely changed height/thickness today. This is trudging slowly to the northeast...and clouds should be thinning tonight in the northeast part of the forecast area...while skies should be clear in the central Shenandoah Valley from early evening on. The clearing skies should lead to good radiational conditions which in turn will lead to fog formation late tonight. Lows in the 50s except lower 60s in the cities.
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&& .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
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After the low pressure area finally departs and moves east of Cape Cod Thursday skies should finally return to a mostly sunny condition - after some early morning fog. Highs in the lower to mid 80s. But the respite from clouds will be short. A cold front will be pushing into the Mid Atlantic Thursday night bringing the chance of showers/isolated thunderstorms. This will not be coming through at a prime time for severe weather. Coverage will be spotty, so one place could pick up a few tenths of an inch of rain while ten miles away stays dry. The front is expected to be east of the region by Friday morning. Skies should improve, highs again in the lower to mid 80s.
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&& .LONG TERM /SATURDAY THROUGH WEDNESDAY/...
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High pressure will be to our southeast with a front along the Mason- Dixon line Saturday and Saturday night. Temperatures will remain warm with a chance of showers or a thunderstorm mainly across the northern half of our region. By Sunday into Sunday night, the high to the southeast will break down with the front sliding across the D.C. area during the day before meandering northward as a warm front Sunday night. The chance for showers and thunderstorms will become more prominant, mainly Sunday with the front nearby and before the warm surge. An increasing southerly wind will usher in warmer and more humid air to help fuel showers and thunderstorms Monday into Monday evening. A strong cold front should works its way eastward across the region Monday night. Gusty westerly winds and drier and cooler air will filter into the region Tuesday and Tuesday night behind the cold front as high pressure builds in from the west. High pressure moves offshore Wednesday, while keeping conditions dry. A return flow will be an indication that a new warm front will try to push across the region later Wednesday.
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&& .AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
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With the exception of CHO all ceilings at airports in our area remain at MVFR levels. Improvement should continue into the evening hours, at which time all sites should return to VFR. Fog development is possible overnight. For now have taken all sites down to 2-3 miles around 09Z-13Z. Later shifts can adjust up/down depending upon latest guidance/obs. VFR after about 13Z Thursday. Showers/isolated thunderstorms possible Thursday night as a cold front moves through. VFR again Friday. Mvfr to ifr conditions expected Saturday through Sunday with showers and thunderstorms in the area near MRB, IAD, MTN and BWI terminals. Vfr conditions elsewhere. Mvfr to perhaps vfr conditions Sunday night. Winds southwest around 5 knots Saturday, becoming light and variable Saturday night, then east 5 to 10 knots Sunday, and southerly 5 to 10 knots Sunday night.
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&& .MARINE...
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Winds expected to remain below SCA values through tonight. On a more southerly flow Thursday will keep winds capped at 15 knots. Showers/isolated thunderstorms will be possible Thursday night. No marine hazards expected Saturday through Sunday night. Winds southwest 5 to 10 knots Saturday, becoming light and variable Saturday night, then east 10 knots Sunday, and southeast 10 knots Sunday night.
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&& .TIDES/COASTAL FLOODING...
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Water levels have decreased slightly with northwest winds today but remain elevated, especially from the Potomac River southward. Straits Point will be near if not exceeding minor flood stage for the next two high tide cycles. Guidance shows steady to decreasing waters for the remainder of the week, but am a bit skeptical about this outcome considering winds will become south or southwesterly through that time. Thus minor flooding at sensitive sites will need to continue to be monitored. In terms of the current guidance, Friday morning will be the next targeted opportunity.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...None. MD...Coastal Flood Advisory from 1 AM to 6 AM EDT Thursday for MDZ017. VA...None. WV...None. MARINE...None.
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&& $$ PRODUCTS...WOODY!/KLW/ADS

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