Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 141920 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 320 PM EDT Mon Aug 14 2017 .SYNOPSIS...
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Weak high pressure will linger over the Mid-Atlantic region through tomorrow. A series of disturbances will move up from the southwest bringing rain chances to our region into tomorrow. A second area of high pressure will build into the region around mid-week, before a cold front slides across the region later in the week.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Clouds and light rain showers will cover the northern half of our region the remainder of the afternoon. Rain amounts are averaging a few hundredths of an inch to one tenth of an inch. Although the NAM represents current rain coverage better than the GFS, it has been about 3 to 4 hours too slow with current showers. With temperatures in the middle to upper 70s and dew point temperatures in the middle to upper 60s, it is making for a rather sticky afternoon in areas that do not receive any rain showers.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY NIGHT/...
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Although we anticipate rain showers to become more widely scattered in the mountains and along portions of the Mason- Dixon region this evening and tonight, there will be some rain showers lingering and other showers developing in parts of the Shenandoah Valley and Virginia Piedmont as well. Very little thunder expected in the rain activity into tonight. In the western Atlantic, Tropical Storm Gert churns up the waters of the western Atlantic before eventually moving north and northeast out to sea through midweek. Weak disturbances and a lingering surface trough will lead to other shower activity Tuesday into Tuesday night. Thunder is possible Tuesday afternoon but limited instability will result in minimal chances. Temperatures will be a couple of degrees warmer with dew point temperatures poking up into the lower 70s in many places. High pressure will build into the region Wednesday into Wednesday night. Drier and slightly cooler conditions will develop over the region.
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&& .LONG TERM /THURSDAY THROUGH MONDAY/...
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A weak upper level ridge will be moving over the region Thursday, while at the surface, a warm front will be advancing back north across the region. The end result will be a significant warm up, with temperatures possibly reaching 90 for the first time in quite a while (since August 4th at DCA, August 2nd at BWI, and July 24th at IAD). With the frontal passage, however, we will have a returning risk of showers and t-storms. We will be solidly in the warm sector on Friday as well, so if we don`t make it Thursday, we could definitely still get there Friday. By then however, a shortwave and cold front will be approaching, which will result in an increased risk of showers and t-storms, perhaps with a severe threat. The timing of the next cold front crossing the region is still a bit uncertain, with various models depicting a range from Friday night to Saturday. However, by Sunday, we should be solidly behind the front with cooler and drier weather taking hold, and likely remaining through Monday.
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&& .AVIATION /19Z MONDAY THROUGH SATURDAY/...
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VFR conditions expected at all terminals with occasional MVFR in light rain showers through tonight or in patchy fog later tonight. Sub-VFR conditions with additional rain showers Tuesday and Tuesday night. VFR conditions Wednesday with high pressure building into the region. Main concern Thursday and Friday will be possible intervals of sub- VFR cigs and vis due to thunderstorms. Risk is mainly afternoon/evening hours both days, as is typical with convection.
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&& .MARINE...
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Winds sub SCA this afternoon through Wednesday night. High pressure will be overhead during the day Wednesday into Wednesday night. Winds mainly sub SCA Thursday and Friday, but will need to watch for potential southerly channeling as a warm front moves through and the next cold front approaches. Other concern will be potential gusty winds with thunderstorms, which will be possible both Thursday and Friday.
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&& .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...None. && $$ SYNOPSIS...KLW NEAR TERM...KLW SHORT TERM...KLW LONG TERM...RCM AVIATION...RCM/KLW MARINE...RCM/KLW

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