Area Forecast Discussion
Issued by NWS Sterling, VA

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399 FXUS61 KLWX 181332 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 932 AM EDT Mon Sep 18 2017 .SYNOPSIS... Warm high pressure will remain over the eastern United States this week. Meanwhile, Hurricane Jose is expected to track north off the Mid Atlantic coast tonight through Wednesday. Refer to the National Hurricane Center`s website hurricanes.gov for the latest on Jose. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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An upper-level ridge will remain over the eastern United States today while surface high pressure over New England wedges down into the Mid-Atlantic. Low level moisture trapped underneath the subsidence inversion has resulted in areas of low clouds and fog. The fog in sheltered valleys west of the Blue Ridge Mountains should burn off by late this morning. Areas of low clouds will gradually dissipate late this morning into early this afternoon...but a broken cu deck will develop for most areas due to the higher amounts of low-level moisture. More warm conditions are expected today along with breaks of sunshine. Max temps will be in the lower 80s across most locations. Limited instability underneath the subsidence inversion may be enough for a couple popup showers west of the Blue Ridge Mountains...but coverage will be isolated and most areas will be dry.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY NIGHT/... By tonight, the forecast will begin to be influenced (indirectly) by Jose, although the bigger influence (again, relatively speaking) will be felt on Tuesday. Northeast/north winds will increase tonight, especially near the Bay, with a fair amount of cloud cover east of the Blue Ridge as well. Will be bringing a chance of showers inland to the western shore by dawn Tuesday, with better chances during the day on Tuesday. The inland reach of these showers likely won`t spread west of I-95, but that is an aspect that is highly conditional on the track of Jose, as well as how much the storm expands as it weakens. A slight nudge westward would increase the potential that an outer band could spread inland, providing a soaking rain. Am still keeping a solution of subsidence in the wake of the cyclone, which will affect the forecast area Tuesday night and Wednesday. && .LONG TERM /THURSDAY THROUGH SUNDAY/... Ridge of high pressure surface and aloft will build over the region Thu through Sun as Jose remains well offshore. Tranquil conditions are expected as a result. Temperatures will remain a few degs above normal during this period. By early next week, the ridge begins to weaken as a weakening post- tropical Jose likely completes another loop and heads back to the mid-Atlc coast. We`ll also be watching Hurricane Maria move into the southwest Atlc during the second half of the week. Recent trends indicate Maria may stay out to sea, but it is really too early to tell at this time. Please refer to NHC for the latest on Jose and Maria. && .AVIATION /14Z MONDAY THROUGH FRIDAY/...
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Low clouds underneath the subsidence inversion has resulted in MVFR cigs this morning. MVFR cigs will be slow to lift...gradually turning to VFR conditions during the early to middle afternoon hours. Jose will make its nearest pass to the terminals late tonight through Tuesday. Significant impacts will likely remain to the east, but northeast winds tonight suggest there may be another round of low clouds to deal with. VFR should prevail Tuesday afternoon through Friday, aside from perhaps early morning fog.
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&& .MARINE...
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The gradient has strengthened a bit...and there have been a few reports of gusts around 18 knots across the middle portion of the Maryland Chesapeake Bay and the lower Tidal Potomac River. A Small Craft Advisory is in effect for these areas today...but it will be marginal. The gradient will strengthen more tonight and SCA conditions are expected across these areas. By Tuesday, the gradient will be at its strongest, with several model solutions suggesting the gales will be possible on the mid Bay. That is contingent on the track of Jose. Have added a Small Craft to all Maryland and DC waters on Tuesday since confidence in 20+ kt gusts high. Would not rule out an upgrade to Gale Warning for a portion of this area. Winds should stay generally below SCA Wednesday through Friday under ridge of high pressure.
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&& .TIDES/COASTAL FLOODING...
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Water levels continue less than a foot above astronomical predictions. This trend should gradually increase over the next couple of days. At this point, St George Island will be the only site forecast to consistently exceed minor flood. Based on strong confidence in the trends, have extended the Advisory for St Marys County for another three tide cycles, through the daytime cycle Tuesday. Elsewhere, model spread precludes action at this time. While moderate flood possible at sensitive locations, confidence in this outcome at the low end of the spectrum. Elevated water levels likely to be a concern through the end of the week.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...None. MD...Coastal Flood Advisory until 4 PM EDT Tuesday for MDZ017. VA...None. WV...None. MARINE...Small Craft Advisory from midnight tonight to 8 PM EDT Tuesday for ANZ531-539. Small Craft Advisory from 6 AM to 8 PM EDT Tuesday for ANZ530- 535-536-538. Small Craft Advisory until 8 PM EDT Tuesday for ANZ532>534-537- 540>543.
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&& $$ SYNOPSIS...HTS NEAR TERM...BJL/HTS SHORT TERM...HTS LONG TERM...LFR AVIATION...BJL/HTS MARINE...BJL/LFR/HTS TIDES/COASTAL FLOODING...BJL

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