Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 151918 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 318 PM EDT Fri Sep 15 2017 .SYNOPSIS... High pressure will dominate the region through Sunday. Tropical Storm Jose is forecast to move north as a hurricane 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 /UNTIL 6 AM SATURDAY MORNING/... Current surface analysis shows a ridge of high pressure centered over the Appalachians and dominating most of the eastern US. However, a weak upper level low, the remnant of Hurricane Irma, is near the New England coast, with a trough trailing back over our region. This trough is providing enough instability for plenty of cumulus, and could spawn a stray shower just about anywhere during the rest of the afternoon into this evening, though best odds are over the higher terrain. Overnight, most cumulus should dissipate, but some mid clouds could linger. Where enough clearing occurs, patchy fog is expected, particularly in the typical locations (Shenandoah and Piedmont). Lows will be mild for mid-September, with low 60s common. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY NIGHT/... Large scale upper level ridge will be building overhead Saturday and Sunday, but a weakness from Irma`s remnants will remain over our region. This combined with warming temps but lingering moisture could once again get a stray shower going, potentially anywhere, but most likely over the terrain. Highs Saturday will be a little warmer than today, with mid 80s more common, but may drop a little Sunday with just a little cooling aloft. Saturday night will be almost a carbon copy of tonight... dissipating clouds followed by patchy fog in the favored spots. Lows look to be a little milder than tonight. However, by Sunday night, Jose may start to influence the weather, with a bit more cloud cover and perhaps a few showers making their way into the middle bay. Lows will remain mild, in the 60s. && .LONG TERM /MONDAY THROUGH FRIDAY/...
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Weather conditions in the long term period will highly depend on how close to the shore Jose tracks. Most likely it will stay relatively dry with perhaps a few showers with the northeasterly flow while Jose moves north to our east. The future track of Jose is highly uncertain with large variations in the model guidance, though concensus and the NHC forecast keeps what is currently Tropical Storm Jose offshore. Keeping in mind the average track forecast errors (increasingly large on days 4 and 5), it is encouraged to monitor the progress of this system. If Jose tracks closer to the shore, there could be an increase in the chance of heavy precipitation, scattered tornadoes, tidal flooding and damaging wind, with greatest odds being east. However, at this time, odds favor minimal impacts. Thursday into Friday weather conditions look dry with upper ridge building in.
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&& .AVIATION /19Z FRIDAY THROUGH WEDNESDAY/... VFR overall through Sunday night. Main concern is the late night and early morning hours when patchy fog may result in IFR cigs and vis at the terminals. Right now, odds of this at DCA are very low, and remain low at BWI. They are slightly higher at IAD, but best chance is at the usual spots, MRB and CHO. Have taken those two sites down to IFR late tonight and they have a good shot at doing it again Saturday night. Otherwise, other than a very isolated shower, its mostly mid clouds and light winds through the weekend. VFR conditions expected Monday-Wednesday, though this is dependent on Jose staying offshore. A track closer to the coast or inland would significantly alter this forecast. && .MARINE... No marine hazards expected through Sunday night with high pressure and light winds. Wind gusts are expected to reach Small Craft Advisory criteria Monday into Wednesday based on the latest forecast track for Jose. Any track shift could alter this forecast, resulting in either higher or lower wind speeds than currently forecast. && .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. 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...None. VA...None. WV...None. MARINE...None. && $$ SYNOPSIS...RCM NEAR TERM...RCM SHORT TERM...RCM LONG TERM...IMR/RCM AVIATION...IMR/RCM MARINE...IMR/RCM TIDES/COASTAL FLOODING...

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