Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 280037 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 837 PM EDT Sat Aug 27 2016 .SYNOPSIS...
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High pressure surface and aloft will hold through Monday then move offshore. A cold front will move through the area Wednesday night. High pressure then builds for the second half of next week.
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&& .NEAR TERM /THROUGH SUNDAY/...
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High pressure is stretched south into the Mid-Atlantic region from northern New England this evening. Light easterly flow will continue off the Atlantic tonight. Low clouds are expected to move into the Chesapeake Bay/ I-95 region by Sunday morning however uncertainity exists as to how far west they get by sunrise. Clouds will dissipate shortly after sunrise. Previous discussion... There will be a slightly better chance of t-storms far west over the Appalachians Sun, but most of the area will remain dry. Slightly cooler with temps in the low 90s.
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&& .SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/...
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Ridge of high pressure begins to weaken over the area Mon as it moves offshore and a shortwave-trough digs across the northeastern states. Increasing warmth and humidity will generate more instability with showers and t-storms becoming more probable over the mtns. Activity will drift east during the late afternoon and/or early evening before dissipating, but is not likely to reach the metro areas. Hot and humid with temps in the mid 90s and heat indices aoa 100F.
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&& .LONG TERM /TUESDAY THROUGH SATURDAY/... Warmer than normal temperatures should persist through the middle part of the week. A few showers and thunderstorms are possible Tuesday afternoon over the higher terrain in a warm and humid airmass but with little forcing outside of terrain circulations. A cold front dropping into the area may be able to bring a threat for showers and thunderstorms closer to the metro areas Wednesday afternoon and evening. A shower or thunderstorm will remain possible Thursday across southern portions of the area as some models/ensembles are slower with the southward progress of the cold front. An unseasonably strong area of high pressure will dive into the region later in the week bringing cooler and drier weather which looks to persist into the first part of next weekend. && .AVIATION /01Z SUNDAY THROUGH THURSDAY/...
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Low clouds possible late tonight at BWI, MTN, and DCA as increasing moisture on easterly flow becomes trapped beneath nocturnal inversion. This was advertised well by early afternoon runs from high-res ensemble guidance (e.g., HRRR-TLE, NARRE). Climatologically, certainty of IFR is higher at BWI and MTN than at DCA. Brief period of MVFR visibilities possible at KCHO, though latest guidance/persistence suggest they may remain VFR. Any low clouds or patchy fog would mix out quickly tomorrow after 13Z. Mainly VFR expected with southwesterly winds around 10 knots Tuesday into Wednesday. A thunderstorm is possible Wednesday as a cold front approaches.
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&& .MARINE... Sub-SCA conditions through Mon. No t-storms expected. The pressure gradient will remain relatively weak Tuesday into Wednesday despite an approaching cold front, with winds likely staying below Small Craft Advisory levels during this time. && .CLIMATE... Ranking of summer 2016 in terms of average temperature (JUN 1 - AUG 26) Site Rank Average Temperature DC 3 80.5 Balt 19 77.2 IAD 3 77.3 && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...None. && $$ SYNOPSIS...LFR NEAR TERM...HAS/LFR SHORT TERM...LFR LONG TERM...DFH AVIATION...MSE/DFH MARINE...LFR/DFH CLIMATE...LWX

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