Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 161342 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 942 AM EDT Sat Sep 16 2017 .SYNOPSIS... High pressure will dominate the region through Sunday. Hurricane Jose is forecast to move north along...but well offshore of... the Atlantic coast early next week. See the National Hurricane Center bulletins for the latest information on Jose. && .NEAR TERM /THROUGH TONIGHT/...
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A ridge of high pressure will remain over the eastern United States through tonight. A small weakness in the ridge remains over our area in the form of an upper-level low. The upper-level low is weak...but there are enough height falls for limited instability to develop this afternoon and early evening. An easterly flow will usher in moisture from the Atlantic as well...and that can be seen currently with dewpoints in the 60s for most locations. Unseasonably warm conditions are expected today due to the upper-level ridge over the eastern U.S. Max temps will be in the lower to middle 80s for most locations. Isolated to scattered popup showers are expected this afternoon and evening due to daytime heating and limited instability. Latest soundings show that convection will be low topped due to the large scale subsidence from the upper-level ridge. Therefore...left lightning out of the forecast at this time and any showers that do occur are expected to be brief. Any showers should cease around sunset. Once again, fog potential will be dictated by clouds overnight. Don`t have a solid feel for where that will/won`t be, but will entertain current thought of patchy fog possible just about anywhere by dawn.
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&& .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... Since the weather regime will be similar Sunday, the forecast will be about the same as well: early morning fog, daytime cumulus developing, with a chance of afternoon showers. The main difference is a better indication for building instability across the highlands... roughly I-81 west...perhaps as soon as mid morning. As such, have morning showers for that area, and included a slight chance of afternoon thunder as well. From a synoptic standpoint, Monday will be similar as well. However, the track of Jose will become more important. Forecast area may be in the subsidence surrounding the cyclone, and have maintained a more stringent PoP approach for the diurnal cycle. Temperatures not far from a MOS mean. With dewpoints rising well into the 60s, overnight lows will be muggy for September. Highs aren`t that far from average. && .LONG TERM /TUESDAY THROUGH FRIDAY/... There is still some degree of uncertainty as to how the tropical system, Jose, will affect our region Tuesday through Tuesday night. The consensus of the computer models tend to keep Jose well offshore of the Tidewater of Virginia and the Delmarva as it moves northward and parallel to the East Coast. Should Jose remain well offshore, about 250 miles offshore, then the best case scenario will be dry conditions for most of our region and a north wind becoming northwest around 10 mph with gusts around 20 mph, mainly over the Chesapeake Bay. Consult the latest bulletins from the National Hurricane Center on Jose. As Jose either moves north toward New England or north then northeast to the nearshore waters of the Eastern Canadian Maritimes Tuesday night through Thursday, dry conditions will develop across all areas. High pressure will build in Wednesday through Friday, ensuring that we will have dry conditions and seasonable temperatures. && .AVIATION /14Z SATURDAY THROUGH WEDNESDAY/... For the next several days, the key features will be similar: early morning fog, then perhaps a few afternoon showers. In terms of restrictions, the fog will be more meaningful. Currently, an extensive mid-level cloud deck have precluded widespread fog formation, although MRB has demonstrated some wild fluctuations. Could have MVFR at IAD before sunrise as well. Confidence at specifics for next couple of days too low to detail here, just the potential is present. Shower coverage should be limited, with low probability of an airfield impact. The best chance probably will be Sunday PM at CHO and MRB. VFR conditions Monday through Wednesday night for all terminals. This is dependent on Jose staying offshore. A track closer to the coast or inland would significantly alter this forecast. && .MARINE... Light flow this weekend, likely becoming onshore in the afternoon. Winds will become increasingly northeast late Sunday into Monday as Jose approaches the waters. Based on the current forecast, likely will need a Small Craft Advisory at some point Monday into Tuesday, and perhaps into Tuesday night. Any track shift could alter this forecast, resulting in either higher or lower wind speeds than currently forecast. No marine hazards expected Wednesday and Wednesday night. && .TIDES/COASTAL FLOODING... Water levels remain a little elevated. They should remain below minor thresholds for the next couple cycles. By Sunday and especially Monday, the approach of Jose may further elevate them, resulting in minor flooding at sensitive sites. The nighttime tide cycle is astronomically preferred. Depending on how close the storm gets, moderate is not impossible, but uncertainty on this is very high at the moment...as seen in the forecast spread via SNAP-Ex. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...None. && $$ SYNOPSIS...HTS NEAR TERM...BJL/HTS SHORT TERM...HTS LONG TERM...KLW AVIATION...BJL/HTS/KLW MARINE...BJL/HTS/KLW TIDES/COASTAL FLOODING...BJL

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