Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 141926 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 326 PM EDT Wed Mar 14 2018 .SYNOPSIS... Low pressure will linger over the Canadian Maritimes for the next couple days. A weak cold front will cross the region on Thursday. Another weak system will pass through the region Saturday. High pressure will return Sunday. A stronger storm system may threaten the region by the middle of next week. && .NEAR TERM /THROUGH THURSDAY/... Deep upper trough attached to the closed low over New England is passing the region at present, and with the warm March sun combined with chilly air aloft, we`ve had plenty of clouds and a few flurries develop. Strong winds have also been mixing down, with widespread gusts of 30-40 mph. This will all continue through early evening, at which point the lack of mixing will allow clouds to diminish, the flurries to dissipate, and the wind to drop off a bit. However, another disturbance will rotate southeast across the region late tonight and Thursday. There will be a strong southwesterly low level jet developing across the region late tonight into Thursday, which will especially increase winds at higher elevations, so have issued wind advisory for the southern Shenandoah Valley and Blue Ridge along with the Potomac Highlands for later tonight and Thursday. Elsewhere, expect winds to stay below 45 mph, but it will be breezy once again. Weak warm advection ahead of a weak cold front will allow temps to warm a bit on Thursday after another chilly night tonight, with lows below freezing rebounding to highs in the 40s to even low 50s. As the system passes, a few showers or flurries may occur, most likely across Maryland, with drier air in place further south and west, except near the Allegheny Front. There, upslope flow will get underway again late tonight and continue through Thursday, with a few more inches of snow likely. We may need to issue another winter weather advisory for these areas, but confidence is not quite there yet. && .SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/... Low pressure will linger nearby on Friday, but with no further upper level disturbances or weak reinforcing cold fronts approaching, the chance of snow showers especially in the mountains will diminish. Temperatures will be a few degrees colder Thursday night and Friday, but big changes in temperatures are not expected. With the low still nearby, it will remain quite gusty, with winds still gusting above 30 mph in the afternoon. Highs will be mostly in the 40s. The next system approaches from the west Friday night. Most guidance is still very slow with it, holding off precip until Saturday, but a few models now bring precip into the region before dawn. Given radiational cooling expected as winds relax Friday night, this could present a wintry mix potential. For now have held POPs at slight chance, but this will need further review. Lows will again be below freezing Friday night. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... High pressure will move in from the northwest heading into the weekend. But a weak trof passing to our southwest could bring some light rain or snow showers (or ZR if early enough in the morning) to the southwest half of our forecast area Saturday. The better chance of precipitation for all comes with a large area of low pressure that moves towards the region from the Plains and Midwest. Current guidance has the low passing directly over our region late Mon and early Tuesday. Of course this late in the winter, with spring starting Tuesday, timing and track will be everything determining precip type. Time will tell. && .AVIATION /19Z WEDNESDAY THROUGH MONDAY/... VFR thru Friday night all terminals. Gusty northwest winds during the daylight hours through Friday, with winds gusting above 20 knots, but they will relax somewhat at night. There can be a stray flurry or sprinkle at times, most likely during the afternoon hours today and Thursday, but they should not present any restrictions. VFR conditions should be the rule until the large low can reach us early next week. && .MARINE... Gale on all waters at present thanks to reinforcing shot of gusty winds rotating around the low. Winds should drop off on all waters slowly tonight, but renewed gusts to just shy of gale are expected again on Thursday. Gusts again drop back a bit Thursday night but likely return Friday. No marine headlines or hazards are expected this weekend. Winds will be on the increase early in the workweek around the large area of low pressure expected to cross the region. && .FIRE WEATHER... Low pressure will remain over the Canadian Maritimes through Friday. High pressure will approach from the north and west during this time. A tight gradient between these systems will bring gusty winds to the area, especially from the late morning through the early evening hours each day. A downsloping west to northwest flow will cause low relative humidity. For Thursday, lower fuel moistures are expected along with gusty winds and low relative humidity. Temps will be in the 40s and 50s, a bit warmer compared to today. There will be an enhanced threat for the spread of wildfires, especially across central Virginia where winds will be strongest and relative humidity will be lowest (near 30 percent). Have issued SPS for this potential. For Friday...more gusty winds are expected. Somewhat chillier conditions may limit the RH drop a bit, but fuel moistures will be quite low. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...Wind Advisory from 2 AM to 8 PM EDT Thursday for VAZ025-026- 503-504-507-508. WV...Wind Advisory from 2 AM to 8 PM EDT Thursday for WVZ505-506. MARINE...Small Craft Advisory from midnight tonight to 6 AM EDT Friday for ANZ530>534-537>541-543. Gale Warning until midnight EDT tonight for ANZ530>543. Small Craft Advisory from midnight tonight to midnight EDT Thursday night for ANZ542. Small Craft Advisory from midnight tonight to 3 AM EDT Thursday for ANZ535-536. Small Craft Advisory from noon Thursday to midnight EDT Thursday night for ANZ535-536. && $$ SYNOPSIS...RCM NEAR TERM...RCM SHORT TERM...RCM LONG TERM...CS AVIATION...CS/RCM MARINE...CS/RCM FIRE WEATHER...RCM/BJL is the U.S. government's official web portal to all federal, state and local government web resources and services.