Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 260112 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 912 PM EDT Mon Jul 25 2016 .SYNOPSIS... A cold front will drift into the region from the north tonight. This front will stall across the region during the middle of the week. Another cold front is expected at the end of the week. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
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Boundary has sunk southward near the region this evening. Earlier convection has dissipated for the most part. Most concentrated areas of activity are across the Philly Metro area and back across portions of northern West Virginia. Still could see some additional showers/thunderstorms develop out ahead of the boundary, especially across parts of eastern Maryland near established convective line and areas from the DC Metro on southward where considerable MLCAPE remains. Can`t rule out an additional pulse severe storm, but threat of organized severe weather is waning. Otherwise...patchy fog possible, especially where rain has fallen today. Lows in the 70s to near 80F.
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&& .SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY NIGHT/... The front will become stalled across Virginia, likely toward the southern half of the area, for Tuesday and Wednesday as it becomes parallel to the upper level flow. Thunderstorm chances will largely be diurnally based each day, but with the front in the area and potential for subtle shortwave troughs to be moving across the area, it will be tough to pinpoint any dry periods. For Tuesday afternoon, bulk shear will again be in the 25-30 kt range in the midst of strong destabilization over the southern portions of the forecast area, so a Marginal Risk of severe weather has been introduced. Wednesday afternoon and evening will need to be monitored as well as the pattern changes very little. High PWAT will mean heavy rain is also a threat. Temperatures will lower a little for the next two days, generally in the low to mid 90s. However, heat indices will approach 100 yet again, especially Tuesday, with the highest values over the far southern areas. Due to values near 105...have issued a Heat Advisory again for Tuesday for Nelson, Albemarle, Orange, and Spotsylvania Counties. Overnights will remain in the 70s. && .LONG TERM /THURSDAY THROUGH MONDAY/... Main story Thursday through the weekend will be persistent above normal temperatures (though not too extreme) and the potential for showers and thunderstorms (some of which could be heavy at times). Front will linger near the area Thursday, which will keep chances for at least isolated afternoon thunderstorms in the forecast. Mid 90s temperatures coupled with upper 60s dewpoints yields heat index values in the upper 90s Thursday. Heights begin to fall late Thursday as shortwave approaches. While timing differences exist among long term guidance, the best chance for precipitation will occur as this feature crosses the area late Thursday into Friday. Depending on the track, there could be some heavy rain across parts of the area. While uncertainty exists with next weekends forecast, general consensus is for above normal temperatures to continue, with at least isolated afternoon thunderstorm chances. && .AVIATION /01Z TUESDAY THROUGH SATURDAY/...
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Mainly VFR expected. Could still be a few showers/thunderstorms this evening and into tonight, but coverage will be lessening. Some patchy fog possible as well, but will leave out of TAFs for now due to limited coverage. Some isolated to scattered additional showers/thunderstorms possible as well Tuesday and Wednesday. Nearby frontal boundary will allow for isolated afternoon thunderstorms Thursday. Better chance for scattered showers/thunderstorms arrives late Thursday into Friday as upper level energy approaches.
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&& .MARINE...
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Southerly winds from 5 to 15 knots will continue this evening before a cold front moves through the waters tonight into Tuesday morning and winds become W to NW behind it. There may be a brief period when winds turn west/northwest where SCA conditions may be approached or met. For now, will plan to handle with Marine Weather Statements if needed. Showers and thunderstorms are possible again Tuesday afternoon mainly across the southern waters and again on Wednesday as the front stalls out. While gradient winds remain below SCA criteria through the end of the week, thunderstorms will be possible Thursday and Friday. The best chance for showers/storms is late Thursday into Friday as upper level energy approaches.
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&& .CLIMATE... The last time we hit 100 degrees: DCA: July 26th 2012 (100) BWI: July 18th 2012 (104) DMH: July 19th 2013 (100) IAD: July 18th 2012 (101) CHO: July 8th 2012 (106) HGR: July 7th 2012 (101) MRB: July 7th 2012 (100) Record maximum temperatures for July 25th: DCA (DC area): 100 (1930) DCA only: 99 (2010, 1987) BWI (Baltimore area): 100 (2010) BWI only: 100 (2010) DMH: 100 (2010) IAD (Dulles area): 98 (2010) IAD only: 98 (2010) CHO: 101 (2010) HGR: 98 (2010) MRB: 101 (1933) DCA (DC area): 79 (1965) DCA only: 79 (1965) BWI (Baltimore area): 77 (1887, 1885) BWI only: 76 (2001, 1965) DMH: 78 (2011) IAD (Dulles area): 76 (1965) IAD only: 76 (1965) CHO: 74 (2010) HGR: 75 (2001) MRB: 73 (2010, 2001, 1989, 1979, 1965) "Area" denotes ThreadEx sites which are the numbers used for RERs. && .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...None. MD...None. VA...Heat Advisory from noon to 8 PM EDT Tuesday for VAZ036-037-050- 056. WV...None. MARINE...None.
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&& $$ SYNOPSIS...ADS NEAR TERM...ADS/MM SHORT TERM...ADS LONG TERM...MSE AVIATION...ADS/MM/MSE MARINE...ADS/MM/MSE CLIMATE...DFH

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