Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 171331 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 931 AM EDT Sun Sep 17 2017 .SYNOPSIS... Warm high pressure will remain over the eastern United States this week. Meanwhile, Hurricane Jose is expected to track north off the coast of the eastern United States during the early to mid week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Large scale upper-level ridge remains over the eastern United States while a weak upper-level trough is situated over New England into the Mid-Atlantic. High pressure remains along the New England coast and an onshore flow continues to usher in more moisture to our area. Any leftover low clouds and fog should burn off by late this morning...allowing for some sunshine. Max temps will reach the lower to middle 80s across most locations...causing another unseasonably warm afternoon. Limited instability will develop as a result of the warmer and more humid conditions...but the subsidence inversion will remain strong. Therefore...isolated to widely scattered showers are expected this afternoon and early evening...but will continue to keep thunder out of the forecast due to the subsidence inversion.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH TUESDAY NIGHT/... Since there will be little change in air mass through Monday, with plenty of moisture and rather low mid-level heights, the forecast will be fairly similar through the period. The challenges will be fog development tonight, especially late at night, followed by diurnal development during the day. The fog will be dictated by where residual clouds reside; have broad-brushed the potential pretty much areawide. As for precip, Jose will be offshore but nearing the Mid-Atlantic by late Monday. While the system likely won`t be affecting the area directly, onshore flow will add to the low-level moisture profile as well as enhancing convergence. Therefore it will be harder to pinpoint where showers may or may not be. Have a 20-30 PoP just about anywhere during the afternoon. Jose`s track most likely will be far enough offshore to preclude impact as it makes its pass Monday night into Tuesday. Only minor PoPs remain in the Bay and adjacent zones. Do have some cloud cover though. While track errors will be less as the cyclone nears, and model guidance is in good agreement, changes are still possible. Please refer to the National Hurricane Center for updates on the forecast regarding Jose. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... The track of Jose becomes very uncertain for the late week, although the potential for significant impacts here is low. Also tropical storm Maria will be the next system to watch for potential U.S. impact next week. Those two Atlantic tropical systems and high pressure over the eastern United States will be the main weather features of note through this upcoming weekend. && .AVIATION /13Z SUNDAY THROUGH THURSDAY/...
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Low clouds and fog should burn off by late this morning for most areas. Isolated to scattered showers are expected this afternoon. Any impact would be limited and brief. Am keeping VFR in the forecast. Tonight and tomorrow will be a carbon copy with respect to concerns, ie: low clouds and fog to start the day followed by widely scattered afternoon showers. Once again, Flight restrictions likely in low clouds and fog, but confidence in details low. Jose will make its nearest pass in its northbound trek Monday night and Tuesday. Impacts should remain east of the terminals, based on the current forecast. Past that, only aviation concern thru Thu is the potential for patchy morning fog.
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&& .MARINE... Winds light, and should remain so into Monday. The gradient increases thereafter as Jose nears the waters. The cyclone will remain well offshore as it heads north Monday night and Tuesday. Small Craft Advisories does appear likely during this time. Gale not out of the question, but its a rather low probability event at this point. Past that, no significant marine concerns through Thu. && .TIDES/COASTAL FLOODING... Water levels running about a half-foot above astronomical normals, but that is sufficient to touch minor flood threshold at St George Island. Elsewhere, caution stages have been met at many sites. Without much flow, suspect the result will be same during the daytime tide cycle today. Water levels will then start to inch upward as Jose nears the mouth of the Chesapeake and forces water into the estuary. There is a wide range of solutions as to how extensive this rise will be. 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. Based on confidence, have extended the Coastal Flood Advisory for St Marys County for two more cycles. It likely will need to be continued beyond that. No other actions have been taken at this point, but Annapolis may be at risk for minor flooding Sunday night/early Monday morning. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...Coastal Flood Advisory until 3 AM EDT Monday for MDZ017. VA...None. WV...None. MARINE...None. && $$ SYNOPSIS...BJL/HTS NEAR TERM...BJL/HTS SHORT TERM...HTS LONG TERM...CAS AVIATION...BJL/HTS MARINE...BJL/HTS TIDES/COASTAL FLOODING...BJL

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