Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 271844 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 244 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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Strong ridge of high pressure sfc and aloft will hold through Sun morning before it begins to drift east. This will continue to suppress convective development over the area. Developing onshore flow tonight will probably result in low cloud development east of the Blue Ridge as suggested by 00Z NSSL WRF ARW and 12z NAM models. The 00Z ECMWF also suggested low clouds rolling in, but the new 12Z has backed off now suggesting low clouds staying over southeast VA. The latest GFS does not indicate low cloud development and instead keeps skies clear overnight. Given the onshore flow and high skill of the NSSL WRF ARW have raised sky cover grids to show a 3-6 hr period of low cigs overnight east of the Blue Ridge. Low clouds then mix out during the mid-late morning. 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/...
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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.
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&& .AVIATION /18Z SATURDAY THROUGH THURSDAY/...
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Potential for low clouds to roll in overnight and affect metro terminals as suggested by 00z ECMWF, NSSL WRF ARW and NAM models. The new 12Z ECMWF has backed off on it suggesting low clouds staying over southeast VA. Introduced a 3-hr period of IFR cigs at BWI, MTN, and DCA and MVFR at IAD. Low clouds 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...
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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.
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&& .CLIMATE...
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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
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&& .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...None. && $$ SYNOPSIS...LFR NEAR TERM...LFR SHORT TERM...LFR LONG TERM...DFH AVIATION...LFR/DFH MARINE...LFR/DFH CLIMATE...

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