Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 190044 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 844 PM EDT Mon Sep 18 2017 .SYNOPSIS...
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A ridge of high pressure will remain over the eastern United States this week. Meanwhile, Hurricane Jose is expected to track north off the Mid Atlantic coast tonight through Wednesday. Refer to the National Hurricane Center`s website hurricanes.gov for the latest on Jose.
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&& .NEAR TERM /UNTIL 7 AM TUESDAY MORNING/...
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A ridge of surface high pressure is in place this evening across the northeastern US with Hurricane Jose well offshore of Cape Hatteras. This has led to low level northeasterly flow across the region. Isolated showers in far outer bands from Jose earlier this afternoon have dissipated, but scattered to broken clouds remain. For tonight, low level moisture is expected to continue to move into the region, increasing the likelihood for a combination of low clouds and fog. Initially may see patchy fog develop in some locations east of the Blue Ridge, but as pressure gradient increases as Jose moves northward, increasing low level wind field becomes more favorable for low stratus instead. For areas west of the Blue Ridge, further removed from the wind field, fog may be more prevalent, however low stratus possible here as well. Additional light showers are also possible close to the Chesapeake, mainly towards morning, as additional bands from Jose approach. Lows tonight generally from 58-68F.
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&& .SHORT TERM /7 AM TUESDAY MORNING THROUGH WEDNESDAY NIGHT/... Jose will pass by well to our east Tuesday before moving well off to our north and east Tuesday night through Wednesday night. Outer bands of showers from Jose will approach areas near and east of Interstate 95 into portions of north-central Maryland Tuesday. The best chance for showers will be near the Bay. Any rain amounts will be light across these areas. Elsewhere...subsidence from a large scale upper-level ridge overhead and behind the tropical system will allow for dry conditions along with some sunshine. Max temps will range from the mid to upper 70s near the Bay where more clouds and possible showers are expected to the lower 80s across most other locations where more breaks of sunshine are expected. Jose will move well off to the north and east Tuesday night while surface high pressure builds overhead. Dry conditions are expected during this time. Another upper-level disturbance will build in from the west later Wednesday into Wednesday night while weak surface high pressure remains overhead. There may be a couple showers across central Virginia into the Potomac Highlands later Wednesday into Wednesday evening...but any instability will be limited so much of the time will be dry. Elsewhere...dry conditions are expected along with more warm conditions. && .LONG TERM /THURSDAY THROUGH MONDAY/... Benign conditions expected in the long term period as upper level ridge/surface high pressure builds over our area Thursday into Monday. Maybe some showers over the ridges, but looking minimal. So, looking at an extended period of dry conditions and high temperatures near 80 of in the low to mid 80s. Remnants of Jose might be lingering off of the Mid- Atlantic/New England coast, away from us, and Maria could be somewhere in the west Atlantic, but it is too early to tell. && .AVIATION /00Z TUESDAY THROUGH SATURDAY/...
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VFR this evening will see an overall downward trend as low stratus and patchy fog develop. Expecting ceilings at our central/eastern TAF sites (IAD, DCA, BWI, MTN) to drop to primarily MVFR, although some localized IFR is possible. At MRB/CHO, where fog may be more of a concern, IFR or sub-IFR is more likely. Low clouds and fog will gradually dissipate Tuesday, but a few showers are possible across the eastern terminals. Even across these areas much of the day should turn out dry with the steadier rain remaining off to the east. High pressure will build overhead for Tuesday night through Wednesday night. Patchy fog cannot be ruled out during the overnight and early morning hours. VFR conditions expected Thursday into Saturday with high pressure built into our area.
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&& .MARINE... Jose will move north offshore tonight and pass by well to our east Tuesday before moving off to the north and east Tuesday night through Wednesday. A strengthening gradient will allow for winds to strengthen through tonight into Tuesday. Will continue with the Small Craft Advisory for the middle portion of the Maryland Chesapeake Bay and lower Tidal Potomac River tonight...and all of the waters Tuesday into Tuesday evening. The strongest winds will be across the southern Maryland Chesapeake Bay Tuesday with gusts around 30 knots likely. A Small Craft Advisory remains in effect for the middle portion of the Bay and lower Tidal Potomac River Tuesday night and it may need to be extended Wednesday for portions of the waters. High pressure will build overhead Wednesday night. No small craft advisory expected between Thursday and Saturday due to low wind speeds over our area. && .TIDES/COASTAL FLOODING... An onshore flow has led to elevated water levels around one half to three quarters of a foot above normal. The elevated water levels will continue through Tuesday morning as the onshore flow strengthens. A Coastal Flood Advisory remains in effect for Straits Point in St. Marys county during this time. Water levels will be close to minor flood thresholds in Annapolis and Washington DC during the high tide cycle late tonight into Tuesday morning. Model spread remains high for later Tuesday and Wednesday. Water may be piled up near the Bay from Jose...but a northerly flow should push water out of the Bay. Will continue with elevated water levels in the forecast with caution stages being met...but confidence in forecast is low and minor flooding cannot be ruled out. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...Coastal Flood Advisory until 4 PM EDT Tuesday for MDZ017. VA...None. WV...None. MARINE...Small Craft Advisory from midnight tonight to 8 PM EDT Tuesday for ANZ531-539. Small Craft Advisory from 6 AM to 8 PM EDT Tuesday for ANZ530- 535-536-538. Small Craft Advisory until 8 PM EDT Tuesday for ANZ542. Small Craft Advisory until 6 AM EDT Wednesday for ANZ532>534- 537-540-541-543. && $$ SYNOPSIS...BJL NEAR TERM...BJL/MM SHORT TERM...BJL LONG TERM...IMR AVIATION...BJL/MM/IMR MARINE...BJL/MM/IMR TIDES/COASTAL FLOODING...BJL

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