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
-- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KLWX 182016 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 316 PM EST Thu Jan 18 2018 .SYNOPSIS...
-- Changed Discussion --
High pressure will build south of the area through the weekend. A cold front will cross the area early next week.
-- End Changed Discussion --
&& .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
-- Changed Discussion --
A ridge of high pressure extends from Louisiana to West Virginia. Skies are virtually clear for the entire eastern United States (east of the Mississippi River) except for along the US-Canadian border. There is still a pressure gradient east of the Appalachians due to an ocean storm off North Carolina. Wind gusts have occasionally gusted to 20-25 kt. Anticipate these winds will decouple late today, if the gradient does not relax before then. Since the area will have clear skies, light winds, and low dewpoints (single digits) tonight, radiational cooling should be favorable. Have trended down toward the lowest of guidance, and the end result may be lower than that for preferred (sheltered) valley locations. Those valleys should easily drop into the teens.
-- End Changed Discussion --
&& .SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY NIGHT/...
-- Changed Discussion --
Warm advection should be underway Friday, with little tangible weather. Aside from perhaps some high clouds, it will largely be a temperature forecast. Readings should get into the 40s Friday (without the winds) and 50s Saturday. Lows will drop into the 20s Friday night and near freezing Saturday night. As an upper disturbance tracks along the Gulf coast Saturday- Saturday night, some moisture could spread north with isentropic lift up the mountains. At this point, there is light qpf (at best)...so PoPs are subsequently low (chance). Will need to keep an eye on temperatures though. Believe that there will be enough warm advection to preclude freezing rain, but a few GEFS ensemble members do have subfreezing air just east of where the meager PoPs will be. And deterministic output also depict a close call. PoPs are only for the western fringe zones, and are only 20-30%, but did introduce rain or freezing rain overnight...just in case.
-- End Changed Discussion --
&& .LONG TERM /SUNDAY THROUGH THURSDAY/...
-- Changed Discussion --
High pressure will be near the South Carolina coast Sunday, with a warm front lifting northward to our west. An area of low pressure will develop along the tail-end of this warm front over the central Plains. The low is expected to move toward the Great Lakes region Sunday night through Monday night. With that, the warm front will bring us a chance for a rain showers along the Mason-Dixon region and the Appalachian Front Sunday night and Monday. The increased chance for rain showers will be Monday night with a cold front passage. Temperatures will be above normal Sunday night through Monday night. High temperatures could reach the 60s Monday ahead of the cold front. Rain showers could linger on Tuesday on the back side of the cold front. Colder and drier air will move in behind the front as well. Temperatures will be about 10 degrees cooler than the day before due to frontal passage. High pressure will regain control of the region with the chilly January air but plenty of sunshine Wednesday through Thursday.
-- End Changed Discussion --
&& .AVIATION /20Z THURSDAY THROUGH TUESDAY/...
-- Changed Discussion --
VFR conditions anticipated into the weekend. Winds will be decreasing this afternoon, and will be light by tonight. Will have winds 10 kt or less, varying between northwest and southwest. VFR conditions Sunday through midday Monday. MVFR to briefly IFR with rain showers late Monday and Monday night.
-- End Changed Discussion --
&& .MARINE...
-- Changed Discussion --
Winds sporadically reaching Small Craft criteria this afternoon; envision a timely expiration based on trends. Flow will back southwest Friday, and will remain there at 10 kt or less through Monday.
-- End Changed Discussion --
&& .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory until 4 PM EST this afternoon for ANZ530>543. && $$ SYNOPSIS...HTS NEAR TERM...HTS SHORT TERM...HTS LONG TERM...KLW AVIATION...HTS/KLW MARINE...HTS/KLW

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