Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 180142 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 942 PM EDT Sun Sep 17 2017 .SYNOPSIS... Warm high pressure will remain over the eastern United States this week. Meanwhile, Hurricane Jose is expected to track north off the coast of the eastern United States Monday through Wednesday. Refer to the National Hurricane Center`s website hurricanes.gov for the latest on Jose. && .NEAR TERM /THROUGH MONDAY/... Large scale upper-level ridge will remain over the eastern United States while a weak upper-level trough remains situated over New England into the Mid-Atlantic. High pressure along the New England Coast will extend south into the Mid-Atlantic through tonight. The onshore flow around the high has allowed for more moisture and it remains unseasonably warm due to the large scale upper- level ridge. Remaining showers should dissipate by midnight. Areas of low clouds and fog are likely late tonight as moisture gets trapped underneath the nocturnal inversion. Fog may be locally dense. A light onshore flow suggests that there may be a better chance of low clouds vs. fog east of the Blue Ridge...but perhaps a better chance for locally dense fog vs. low clouds west of the Blue Ridge. && .SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/... High pressure will continue to wedge into the area from New England Monday and there will be a weakness overhead in the large scale upper-level ridge. Therefore...more of the same is expected when compared to recent days. Areas of low clouds and fog will burn off by late morning...and more unseasonably warm conditions are expected with max temps in the lower 80s across most areas. Shower coverage will remain isolated to widely scattered and most areas will end up dry. Jose will move north up the Mid-Atlantic Coast Monday night through Tuesday night. Jose is most likely to remain far enough offshore to prevent any significant impact on our area. Outer bands of rain will make a push toward our CWA during this time. Will keep slight chance pops across our eastern areas. As of now...it appears that much of the time will be dry and that most rainfall should stay to our east. However...should Jose track just a bit farther west then a soaking rain is possible across our eastern areas. Will have to closely monitor the track of Jose over the next couple days. For the latest information regarding the track of Jose...please refer to the National Hurricane Center`s website hurricanes.gov. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... Wednesday-Friday: By 12Z Wed...Jose will have weakened to a tropical storm and moved well north of the area. Subsidence expected on the periphery of Jose over our area could allow temps to spike up on Wed even with northerly winds. By Wed night into Thur...a large upper-level high pressure system over the Great Lakes will build eastward...but just how far east will depend on the the future track of Jose of the New England coast. For our region, weak high pressure is expected in the wake of Jose for the remainder of the work week Thursday and Friday. Temperatures are expected to average above normal Wednesday through Friday. With northerly/northeasterly winds expected Wed-Fri, would also expect to see some locally dense fog set up in favored valley locations...and even the DC/Baltimore metro areas could see locally dense fog around sunrise (or just after) for an hour or two. There`s a suggestion in some models of a weak backdoor cold front poised to the north of our region early Friday. This front will sag southward on Friday...and could bring a cooler and more moist maritime influence to the northeastern and eastern zones Friday. This front would dissipate late Friday. For the weekend...surface ridge of high pressure extending from New England into North Carolina will control the weather. && .AVIATION /02Z MONDAY THROUGH FRIDAY/... Generally VFR conditions currently...but more low clouds and fog are likely later tonight into Monday morning. IFR and subIFR conditions are possible. Cigs/vsbys should improve Monday morning. An onshore flow will continue Monday night through Tuesday night. Low clouds are possible during this time...especially during the overnight and morning hours. Expect mostly VFR conditions through the extended with IFR to locally LIFR visibilities in early morning fog at IAD/MRB...and MVFR/IFR fog for BWI/DCA/CHO/MTN terminals. && .MARINE... An onshore flow will continue through Monday morning...but winds should remain below SCA criteria. The gradient will strengthen as Jose moves north off the Mid-Atlantic coast later Monday through Tuesday night. Have issued Small Craft Advisory through Monday night and will likely need to extend through Tuesday night. A Gale Warning may be needed for portions of the waters as well...particularly across the southern Maryland Chesapeake Bay late Monday night through Tuesday. Small craft winds possible Wednesday depending on how fast Jose moves away. The pressure gradient will diminish Wednesday afternoon...and sub advisory winds/waves are expected for the remainder of the week. && .TIDES/COASTAL FLOODING... Onshore flow will continue through tonight...but it will be light. Elevated water levels around one half foot to three quarters of a foot above normal are most likely. This will cause water levels to be close to minor flooding thresholds for sensitive areas. Confidence remains highest for Straits Point in St Marys County where a Coastal Flood Advisory remains in effect. Annapolis and Washington DC will also be close overnight into early Monday morning and this will have to be monitored throughout this remainder of the night. The onshore flow will strengthen a bit for Monday into early Tuesday as Jose moves north off the Mid-Atlantic Coast. Water levels will likely increase and there is a better chance for minor tidal flooding...especially during the preferred high tide overnight Monday into early Tuesday. Depending on how close the storm gets, moderate is not impossible, but uncertainty on this is very high at the moment. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...Coastal Flood Advisory until 3 AM EDT Monday for MDZ017. VA...None. WV...None. MARINE...Small Craft Advisory from midnight Monday night to 6 AM EDT Tuesday for ANZ531-532-539-540. Small Craft Advisory from 6 PM Monday to 6 AM EDT Tuesday for ANZ533-541-542. Small Craft Advisory from 3 PM Monday to 6 AM EDT Tuesday for ANZ534-537-543. && $$ SYNOPSIS...BJL NEAR TERM...BJL/RCM SHORT TERM...BJL LONG TERM...SMZ AVIATION...BJL/SMZ/RCM MARINE...BJL/SMZ/RCM TIDES/COASTAL FLOODING...BJL/RCM

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