Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 200758 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 358 AM EDT Wed Sep 20 2017 .SYNOPSIS...
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A ridge of high pressure will remain over the eastern United States through early next week. Hurricane Maria may approach the coast of the Carolinas by the middle of next week.
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&& .NEAR TERM /THROUGH TONIGHT/...
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Showers have mostly dissipated across the region as a lingering outer band of Jose pushes westward. Could still be a sprinkle out there, but nothing more than that expected early this morning. Otherwise, high pressure continues to dominate across the Appalachians, while Tropical Storm Jose is still located off the Delmarva and continues heading northeast away from us. Though high pressure is present aloft, there is a weak upper level low aloft over Ohio. Thanks to light winds and clearing skies plus moist low levels, patchy fog has developed. This fog may become locally dense, but at this point do not expect a need for a dense fog advisory. Through the day, any fog should dissipate mid morning, and it should turn out partly to mostly sunny. However, while subsidence around Jose should prevent showers near the metro, the upper low over Ohio is expected to dive southeast into the Appalachians and weaken. This may allow enough instability for a shower or thunderstorm across our southwestern zones in eastern WV and western VA. Otherwise, the increased sunshine and subsidence plus warmer air aloft should result in above normal temps, with highs in the mid-upper 80s. Tonight, surface high pressure remains, so it should turn out mostly clear after any cumulus (or CB in SW zones) dissipates. Patchy fog will again be a concern. Lows will be mainly in the 60s.
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&& .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
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Northeast flow aloft will dominate Thursday through Friday night as ridge builds to our west and Jose stalls to the east. Jose should have little to no effect on our weather during this time, so it will be unseasonably warm and humid, but dry, with the ridging preventing any convection. Highs will be in the mid to upper 80s, with lows in the 60s. Patchy late night and early morning fog will be the main forecast concern, mainly in the more rural, inland locations.
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&& .LONG TERM /SATURDAY THROUGH TUESDAY/...
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Ridge of high pressure will gradually strengthen through early next week. Latest Euro is much stronger than GFS/GEFS with the h5 ridge showing a 591 decameter ridge. No wx is expected as a result. The first half of next week, flow will turn more onshore north of Hurricane Maria. Latest Euro has trended westward and slower with the track of Maria bringing it closer to the NC Outerbanks, but so far models have been inconsistent on track longitude thus far, limiting confidence. Please refer to NHC for the latest on Maria.
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&& .AVIATION /08Z WEDNESDAY THROUGH SUNDAY/...
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Patchy fog is developing in parts of the area and MRB has already gone IFR as of this writing. CHO is possibly next, and a chance (albeit much smaller) exists for IAD and BWI. DCA has little chance of IFR or even MVFR this morning. For locations where the fog does develop, it should dissipate mid morning with VFR presiding rest of the day. Patchy fog will be a concern again over the next several late night and early morning periods thanks to persistent high pressure and light winds. Best odds same as early this morning as described above. Other than that, should be VFR thru Friday night. VFR conditions through Sun with no sig wx.
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&& .MARINE...
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Winds gradually declining as Jose slowly moves northeast away from the area. SCA ends on much of the waters around 6AM and remaining waters near noon. Might need to add/extend SCA for some waters this afternoon with mixing resulting in a little higher gusts despite Jose`s movement away, but uncertainty is high so have not done so yet. From tonight through Friday night, high pressure and light winds will dominate, with no SCA concerns at present. Light winds through the weekend. Winds will start strengthening during the first half of next week as pressure gradient tightens in response to approaching Hurricane Maria.
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&& .TIDES/COASTAL FLOODING...
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Minor coastal flooding appears will continue for the foreesable future from Annapolis south to Straits Point.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...None. MD...Coastal Flood Advisory until 6 PM EDT this evening for MDZ018. Coastal Flood Advisory until 10 PM EDT this evening for MDZ014. Coastal Flood Advisory until 7 PM EDT this evening for MDZ017. VA...None. WV...None. MARINE...Small Craft Advisory until 6 AM EDT early this morning for ANZ532-540. Small Craft Advisory until noon EDT today for ANZ533-534-537- 541-543.
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&& $$ SYNOPSIS...LFR NEAR TERM...RCM SHORT TERM...RCM LONG TERM...LFR AVIATION...RCM/LFR MARINE...RCM/LFR TIDES/COASTAL FLOODING...LFR

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