Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 230802 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 402 AM EDT Sat Sep 23 2017 .SYNOPSIS... Surface and upper level high pressure will remain in place through the weekend and into early next week. The high will slowly weaken its grip over the area by the middle of the week as Hurricane Maria moves northward through the Western Atlantic. && .NEAR TERM /THROUGH TONIGHT/... Have seen some patchy, locally dense fog early this morning, especially in the Frederick, Maryland area, and in the Manassas-Warrenton corridor of northern Virginia. It would probably be more widespread, but some high clouds remain over the Shenandoah Valley and Potomac Highlands. Once the fog burns off this morning, it will be another largely sunny and unseasonably warm day. Highs should be at least a couple degrees warmer than yesterday...mostly in the mid 80s. Overnight, another possibility for patchy fog to develop with lows mainly in the 60s, except in the urban centers, where temperatures may stay around 70. && .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... On Sunday and Monday, the upper ridge is at its strongest over our area, which should also yield the warmest (dare I say hottest?) temperatures of this stretch. Can`t rule out that we hit 90 in some spots. Even 89 degrees would be the warmest we have seen in over a month. Dewpoints will start creeping upward too, and that means uncomfortable humidity levels for late September, but nothing to spark any precipitation through Monday night. && .LONG TERM /TUESDAY THROUGH FRIDAY/... The long term period will be dominated by attention to Hurricane Maria. On Tuesday, ridge axis will be to our north, with Maria pushing northwest from the south. Latest guidance has shifted a bit west somewhat, bringing the storm closer to the North Carolina Outer Banks than previous runs. Guidance now stalls the storm just southeast of the Outer Banks Wednesday before the next strong upper trough and cold front moving in from the northwest finally starts kicking it out to sea on Thursday. While most guidance still does not show a significant impact in our region, attention should continue to be paid to this storm until it moves safely out to sea. Please refer to the latest products from the National Hurricane Center for the most up-to-date information on Hurricane Maria. Behind the cold front (which could bring a few showers regardless of what Maria does), temperatures will drop significantly Friday into Saturday. The long September warm spell looks likely to end. && .AVIATION /06Z SATURDAY THROUGH WEDNESDAY/... MVFR visibility possible at CHO/MRB/IAD this morning and again tonight. Otherwise, VFR with light winds and just a few clouds through the valid TAF period, and continuing through Monday. Attention will be on Hurricane Maria during Tuesday and Wednesday. While sub VFR conditions are not likely, a gusty northwest breeze of 15-20 knots is possible, as are a few showers. A further deviation northwest in the track of Maria could bring worse conditions. Refer to latest NHC statements for up-to-date information on Maria. && .MARINE... High pressure will allow for light winds around 10 knots or less through the weekend. Perhaps some patchy fog on the waters overnight. SCA winds looking likely across the waters on Tuesday and Wednesday as Hurricane Maria approaches and we get enveloped by its expanding wind field. A few showers will also be possible. If the storm`s track deviates further northwest, more significant impacts are possible (though not likely). Refer to latest NHC statements for up- to-date information on Maria. && .TIDES/COASTAL FLOODING... September is always a prime month for tidal flooding and this is proving to be no exception. Minor coastal flooding is forecast to persist through this morning`s tide cycle and likely this afternoon`s tide cycle from Annapolis southward on the western shore of the Bay and on the lower tidal Potomac. Outlook...DC will be close to minor threshold with tonight`s tide cycle if current tidal departures rise at all. Straits Point (St. Mary`s Potomac side) will likely continue to see tidal flooding around high tide through at least the Sunday afternoon tide cycle. Elsewhere, things are more in question due to the light winds. Local research has shown that in light wind regimes, the tidal anomaly locally is more controlled by what`s coming in to the lower Bay. Those anomalies are currently higher than what we have locally, and seem unlikely to drop much, so our forecast might prove to be optimistically low on Sunday/Monday. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...Coastal Flood Advisory until 10 PM EDT this evening for MDZ018. Coastal Flood Advisory until 1 AM EDT Sunday for MDZ014. Coastal Flood Advisory until 9 PM EDT this evening for MDZ017. VA...None. WV...None. MARINE...None. && $$ SYNOPSIS...JE NEAR TERM...JE SHORT TERM...JE LONG TERM...RCM AVIATION...JE/RCM MARINE...JE/RCM TIDES/COASTAL FLOODING...JE is the U.S. government's official web portal to all federal, state and local government web resources and services.