Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 191339 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 939 AM EDT Tue Sep 19 2017 .SYNOPSIS... A ridge of high pressure will remain over the eastern United States through early next week. Meanwhile, Hurricane Jose is expected to track north off the Mid Atlantic coast through Wednesday. Refer to the National Hurricane Center`s website hurricanes.gov for the latest on Jose. && .NEAR TERM /THROUGH TONIGHT/...
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A ridge of high pressure will remain overhead through tonight while surface high over northern New England wedges down into the Mid-Atlantic. Jose will continue to move northward...passing us by well offshore. Low-level moisture trapped underneath the subsidence inversion has resulted areas of low clouds this morning...especially east of the Blue Ridge and Catoctin Mountains. The low clouds should gradually mix out late this morning through this afternoon. Increasing sunshine will allow for more warm conditions with max temps in the lower 80s across most areas. For locations near the Bay...moisture from Jose will bring more clouds and perhaps even an isolated shower. However...most of the time will be dry. Highs in the mid to upper 70s are expected close to the Bay. Jose will continue to move off t the northeast tonight while high pressure builds overhead. More mild conditions are expected with min temps ranging from the 50s n the Potomac Highlands to the mid and upper 60s in downtown Washington and Baltimore. Areas of fog are expected overnight...especially across central Virginia and for valley locations west of the Blue Ridge Mountains. This is where the flow will light and the atmosphere is most likely to decouple. Farther east...fog is less likely because of a sustained light northwest flow behind Jose.
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&& .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
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Ridge of high pressure will be gradually strengthening over the region Wed through the weekend keeping generally warm and dry conditions. Models, however, do show a shortwave-trough over the OH valley weakening as it approaches the Appalachians. These could result in a few diurnal showers over the mtns.
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&& .LONG TERM /FRIDAY THROUGH MONDAY/... A firm ridge of high pressure will ensure that our region remains dry with warm temperatures Friday through Monday. A stray shower or two can`t ruled out over the highest ridges of the Potomac Highlands due to daytime heating. High temperatures could be about 10 degrees above average for this third week of September. Highs ranging from near 80 in the western ridges and along the coastal waters of the Chesapeake Bay to the middle 80s elsewhere. Remnants of Jose could still linger off of the mid-Atlantic Coast or somewhere south of southern New England and the tropical system, Maria, may try to move northward from near the Bahama Islands and be somewhere in the western Atlantic. There are still uncertainties with both tropical features. Check out the National Hurricane Center`s website on both features. && .AVIATION /14Z TUESDAY THROUGH SATURDAY/...
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MVFR cigs should gradually lift to VFR levels late this morning into early this afternoon for the eastern terminals. Skies clear tonight but patchy dense fog could develop at the usual sites like KCHO and KMRB. VFR conditions Friday through Monday. Winds generally northeast around 5 knots each afternoon, then light and variable each night.
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&& .MARINE...
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Will continue with a Small Craft Advisory for the waters into this evening...but it will be marginal across the upper Tidal Potomac River and northern Chesapeake Bay. Will continue with a Small Craft Advisory for the middle portion of the Bay and the lower Tidal Potomac River tonight...and it may need to be extended into Wednesday. Winds will diminish later Wednesday through Thursday as high pressure builds overhead. No marine hazards expected Friday through Monday. Winds northeast 5 to 10 knots each afternoon, then northeast around 5 knots each night.
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&& .TIDES/COASTAL FLOODING...
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Minor coastal flooding expected at Straits Point over the next several high tide cycles. CF.Y has been extended. Elsewhere...a northwest wind may keep water levels below minor flood thresholds but confidence is low because of a build up of water near the mouth of the Chesapeake Bay. This water will try to come back north up the Bay during the next high tide cycle tonight into Wednesday...despite the northwest flow.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...None. MD...Coastal Flood Advisory until 6 AM EDT Wednesday for MDZ017. VA...None. WV...None. MARINE...Small Craft Advisory until 8 PM EDT this evening for ANZ530- 531-535-536-538-539-542. Small Craft Advisory until 6 AM EDT Wednesday for ANZ532>534- 537-540-541-543.
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&& $$ SYNOPSIS...BJL/LFR NEAR TERM...BJL/LFR SHORT TERM...LFR LONG TERM...KLW AVIATION...BJL/LFR/KLW MARINE...BJL/LFR/KLW TIDES/COASTAL FLOODING...BJL

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