Area Forecast Discussion
Issued by NWS Sterling, VA

Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KLWX 301823 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 223 PM EDT Tue Aug 30 2016 .SYNOPSIS... High pressure will remain over the Mid Atlantic today, moving offshore Wednesday ahead of an approaching cold front. The cold front will move through the area Wednesday night. High pressure returns late in the week, lasting through the weekend. && .NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
High pressure the main surface feature today impacting the region, resulting in predominately dry conditions. Hi-res models still hinting at convection over the mountains this afternoon where the best surface convergence lines up. But with a drier airmass in place as noted by the much lower PWs today than yesterday, really not expecting much in coverage. Plenty of sun will allow for temps to warm into the upper 80s to lower 90s. Any thunderstorms that form will dissipate this evening. Dry overnight with patchy fog possible in the valleys of the western CWA.
-- End Changed Discussion --
&& .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
-- Changed Discussion --
A change in the pattern finally Wednesday as the high moves out of the area as a cold front slowly moves in from the west. 12Z models slightly slower the previous model runs, bringing the front into the western areas late in the day Wednesday and eventually pushing it south on Thursday. As such, have slowed PoPs with the best chance late in the day and through Wednesday night. As such, could very well end up being more just showers though cannot rule out isolated thunderstorm right along the front tomorrow night. The front finally exits the region by midday Thursday, so carrying over PoPs for the eastern half Thursday morning. A pop up shower or thunderstorm will be possible Thursday afternoon into evening as the upper level trough and associated energy lag behind a bit, finally moving through Thursday night.
-- End Changed Discussion --
&& .LONG TERM /FRIDAY THROUGH TUESDAY/...
-- Changed Discussion --
A large area of high pressure will sprawl southward out of Canada towards the region Friday, then pass to the north over New England and into the northwestern Atlantic over the weekend. This high pressure will be accompanied by a much cooler and drier airmass (850 mb temperatures around 10 C and PWATs of around 0.75 inches). This will likely lead to highs in the mid 70s to lower 80s and lows in the 50s to lower 60s through the first half of the weekend, which is around 5 degrees below normal for this time of year. Whatever becomes of Tropical Depression 9 looks to pass south and east of the area over the weekend, but it could linger offshore a bit if it gets trapped by the building high. Of note, the 12z guidance has exhibited a westward shift in the eventual track of TD 9 which may bring at least fringe effects of precipitation to parts of the area over the weekend. Since this is the first model cycle to indicate a further west track, the forecast for this time range is highly uncertain. For the latest on TD 9 please see products issued by the National Hurricane Center. A gradual warming trend is expected to ensue during the first half of next week, but the rate of warming will depend on how quickly high pressure is able to re-establish itself in the wake of any departing tropical system over the western Atlantic.
-- End Changed Discussion --
&& .AVIATION /18Z TUESDAY THROUGH SUNDAY/...
-- Changed Discussion --
Generally VFR conditions through the TAF period. Patchy fog may develop tonight at KCHO. Showers and thunderstorms will be possible Wednesday into Wednesday night at all TAF sites as a cold front moves through the Mid Atlantic and possibly lingering into Thursday. This could bring brief sub-VFR conditions. Mainly VFR is expected Friday into Saturday with northerly flow around 10 knots. Some higher gusts are possible during this time. Lower ceilings and higher wind gusts are possible over eastern terminals by Saturday afternoon depending on the eventual track of TD 9.
-- End Changed Discussion --
&& .MARINE...
-- Changed Discussion --
Generally sub-SCA conditions on all waters. A cold front will push through the waters Thursday morning which may cause thunderstorms to develop. A Small Craft Advisory may be needed Thursday afternoon and through Friday with increasing northerly winds behind front. Higher wind gusts are possible over the waters this weekend depending on the eventual track of TD 9.
-- End Changed Discussion --
&& .CLIMATE... Ranking of summer 2016 in terms of average temperature (JUN 1 - AUG 29) Site Rank Average Temperature DC 3 80.6 Balt 14* 77.3 IAD 3 77.4 * tied with 1937, 1944, 1994, and 2006 && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...None. && $$ SYNOPSIS...Sears NEAR TERM...Sears SHORT TERM...Sears LONG TERM...DFH AVIATION...Sears/DFH MARINE...Sears/DFH CLIMATE...LWX

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.