Area Forecast Discussion
Issued by NWS Sterling, VA

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
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 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
278 FXUS61 KLWX 221852 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 252 PM EDT Sat Oct 22 2016 .SYNOPSIS... Surface high pressure will build south of the area through the remainder of the weekend as low pressure pulls away into the Canadian Maritimes. A reinforcing cold front will move through Monday with cool high pressure to follow for mid week. A low pressure system will approach from the west late in the week. && .NEAR TERM /THROUGH TONIGHT/... Deepening low pressure is located over Maine this afternoon as high pressure builds over the southern MS Valley. The tight pressure gradient has been resulting in strong winds. The few hours of 40 kt wind gusts during late morning/midday may have been the peak, as KLWX VWP shows 40 kt winds now located around 7kft. This evolution generally agrees with forecast soundings. However, will leave Wind Advisory in effect for now as gusts near 40 MPH are still notable. Low level winds are expected to strengthen/lower this evening, although nocturnal stabilization should prevent stronger gusts from reaching the surface. It will still be a breezy night (except perhaps in sheltered valleys). Ridgetops will remain windy, but low confidence on magnitude since CAA pattern will be reversing. Within our CWA, we have only received one reports of flurries in Grant County, although favorable upslope areas are likely still seeing off and on rain and snow showers. This activity should diminish by this evening as moisture, lift and wind direction become less favorable. Lows tonight will be in the 40s for most with lower to mid 30s in higher elevations. && .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... Main trough axis lifts to the northwest for Sunday and Sunday night which will allow for dry weather. Since we will still be in the gradient with low pressure to the NE and high pressure to the SW, it will still be breezy with 20-35 MPH gusts during the day. Under weak warm advection, temperatures should recover 5-8 degrees. A reinforcing cold front will drop south into the area on Monday. It will be moisture starved though, with only a small chance of showers in the highlands. High temperatures will depend on the timing of frontal passage, with southern areas standing the best chance to see highs reach the 70+. The wind will still be noticeable as well with gusts of 20-30 MPH. High pressure will build from the west Monday night with lows returning to the 30s and 40s. && .LONG TERM /TUESDAY THROUGH SATURDAY/... Long term starts out with a big closed low over Atlantic Canada and fast northwest flow on its southwestern flank over our region. This low will very slowly shift east out into the Atlantic so that by early Thursday a weak ridge is located over our region. This will quickly be followed by a sharp trough which will move in Thursday night. After that uncertainty grows with some guidance pushing the shortwave through but leaving the longwave trough in place...while other guidance cuts off a deep low over the region aloft. For our sensible weather at the surface, this translates to high pressure slowly building in with diminishing northwest winds Tuesday. While the surface high doesn`t build directly overhead, it will be close enough such that we could have a good radiational night on Tuesday night, perhaps enough to bring frost into suburbs again. High pressure remains to our north influencing our weather on Wednesday into Wednesday night, but by Thursday, the next surface low pressure will be approaching from the west with increasing clouds and rain chances. Depending on the progress of the system, the rain may continue into Friday or even Friday night, or end fairly quickly. This is still pretty uncertain. Overall, temps will stay below normal, with the coolest period likely Tuesday with a little warming possible just ahead of the front on Thursday. && .AVIATION /18Z SATURDAY THROUGH THURSDAY/... The primary aviation impact for the TAF period (and to some extent through Monday) will be the wind. NW gusts to 35 kt will remain possible through late afternoon. They will abate some tonight, but westerly gusts of 20-30 kt are expected on Sunday. Otherwise, VFR conditions are expected with only some cumulus clouds around FL050. A cold front will pass through Monday, with winds becoming NW again with gusts 20-25 kt. VFR overall Tuesday through Wednesday night outside of any early morning fog, which would mainly CHO/MRB/IAD. Sub-VFR cigs/vis possible Thursday on as a storm system brings rain back to the region. && .MARINE... NW gales continue through the afternoon. Should see the more sheltered waters decrease to Small Craft Advisories by late afternoon, with other waters not following suit until late tonight. For now, have allowed a decrease in winds for the upper Potomac and Patapsco tonight, but this is not certain. Otherwise Small Craft conditions will likely continue through Monday night (westerly Sunday, then northwest again Monday with a frontal passage), especially on the wider parts of the Bay. Will allow future headlines to be refined as near-term headlines become resolved. Overall looking like winds will diminish through Tuesday with sub- SCA likely by Tuesday night. Southerly channeling could bring winds back to SCA levels Wednesday night or Thursday, but this is still highly uncertain. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...Wind Advisory until 5 PM EDT this afternoon for DCZ001. MD...Wind Advisory until 5 PM EDT this afternoon for MDZ003>006-011- 013-014-016-018-503>508. VA...Wind Advisory until 5 PM EDT this afternoon for VAZ025>031- 052>054-501-503>508. WV...Wind Advisory until 5 PM EDT this afternoon for WVZ051>053-055- 501-502-505-506. MARINE...Small Craft Advisory from 2 AM to 8 PM EDT Sunday for ANZ531>534-539>541-543. Gale Warning until 2 AM EDT Sunday for ANZ531>534-539>541-543. Small Craft Advisory from 6 PM this evening to midnight EDT tonight for ANZ535-536-538. Gale Warning until 6 PM EDT this evening for ANZ530-535>538- 542. Small Craft Advisory from 6 PM this evening to 8 PM EDT Sunday for ANZ530-537-542. && $$ SYNOPSIS...ADS NEAR TERM...ADS SHORT TERM...ADS LONG TERM...RCM AVIATION...ADS/RCM MARINE...ADS/RCM is the U.S. government's official web portal to all federal, state and local government web resources and services.