Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 290114 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 914 PM EDT Sun Aug 28 2016 .SYNOPSIS... High pressure will remain over the Mid Atlantic through Monday before moving offshore. A cold front will move through the area Wednesday night. High pressure returns for late in the week. && .NEAR TERM /THROUGH MONDAY/...
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Ridge of high pressure persisting over the region through tonight with subsidence leading to generally dry conditions. A weak surface trough over western PA combined with weak mid level shortwave energy has triggered showers and thunderstorms across a good portion of the state. However, airmass over our CWA stable enough to preclude anything more than a stray shower or thunderstorm into the far northwestern corner around midnight.
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&& .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
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Upper level trough swings through Monday with a surface front passing to the north, looking to be washed out south of the Mason-Dixon. Region will then be on the eastern periphery of surface high pressure as well as the eastern side of ridging building across the central US. Moisture advection on the surface flow which could result into a bit more of instability Monday afternoon, so cannot rule out scattered showers and thunderstorms over the higher terrain of the western CWA, but generally staying west of the Blue Ridge. Anything that forms will weaken overnight Monday. The ridge weakens on Tue allowing for better chances of convection especially west of the Blue Ridge, but still not likely to reach the metros.
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&& .LONG TERM /WEDNESDAY THROUGH SUNDAY/...
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A cold front will drop into the area from the northwest Wednesday into Wednesday night. The operational GFS runs the last day or so have wanted to push the surface front south ahead of the 850 mb front, which means northerly low-level flow by the time any forcing gets here. This is not totally out of the question given the anomalously strong surface high building in behind the front, but a few showers and thunderstorms will still be possible in the frontal zone late Wednesday afternoon and Wednesday evening. GFS/ECMWF have 850 mb temperatures dropping into the 12-15 C range behind the front for the latter portion of the week indicating a potential for temperatures several degrees below normal. The airmass will be much drier on a northerly flow as well. A few ensemble members of the GEFS/EC indicate a potential for some shower activity moving north associated with Gulf of Mexico moisture late in the upcoming weekend. Temperatures and humidity will begin to rebound during this time as well.
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&& .AVIATION /01Z MONDAY THROUGH FRIDAY/...
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Few aviation impacts expected through tomorrow afternoon with generally light/variable winds. Only low chance of MVFR possible at KCHO/KMRB due to patchy fog prior to sunrise. Low chance of TSRA at KMRB tomorrow afternoon, though kept out of the TAF due to low probability. A shower or thunderstorm is possible late Wednesday afternoon or evening along a cold front. Southerly flow less than 10 knots Wednesday will become northerly Wednesday night and increase to 10 to 15 knots Thursday with a few gusts possible.
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&& .MARINE...
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Occasional easterly gusts to 20 knots this evening, have covered with MWS. Otherwise sub-SCA conditions on all waters through Wednesday. Northerly flow behind the front could result in SCA level gusts Thursday.
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&& .CLIMATE... Ranking of summer 2016 in terms of average temperature (JUN 1 - AUG 27) Site Rank Average Temperature DC 3 80.5 Balt 18 77.3 IAD 3 77.3 && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...None. && $$ SYNOPSIS...LFR NEAR TERM...Sears SHORT TERM...Sears/LFR LONG TERM...DFH AVIATION...MSE/DFH MARINE...Sears/DFH CLIMATE...LWX

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