Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 220714 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 314 AM EDT Sun Oct 22 2017 .SYNOPSIS...
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High pressure will push eastward into the northwest Atlantic through Monday. Low pressure will move up the Appalachians Monday night into Tuesday. Upper troughing will remain over the region through the second half of the week.
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&& .NEAR TERM /TODAY/...
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Patchy fog early this morning, mainly near the Chesapeake Bay and in sheltered river valleys. Another delightful day is in store for the Mid-Atlantic. Basically a carbon copy of Saturday with some high cirrus, light winds, and unseasonably warm temperatures in the 70s. Enjoy it while it lasts, because the area of high pressure responsible for the gorgeous weather packs its bags and heads into the north Atlantic by tonight.
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&& .SHORT TERM /TONIGHT THROUGH TUESDAY NIGHT/...
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As high pressure sails away into the north Atlantic Sunday night into Monday, low pressure will begin to move northeastward up the Appalachians. This area of low pressure will be re- invigorated by a digging shortwave trough diving across the Great Lakes and Ohio Valley. The result will be widespread beneficial rain Monday night into Tuesday across the region (generally 0.50-1.00", locally 2" in heavier downpours/on the ridges). Model guidance has unanimously trended quicker which reduces the already meager outlook for flooding potential. Gusty winds and a few claps of thunder are still possible, though a little less likely given unfavorable timing in the diurnal cycle. The low will depart to the northeast Tuesday sending a cold front through. This will knock temperatures back to more seasonable levels.
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&& .LONG TERM /WEDNESDAY THROUGH SATURDAY/...
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We have been running over ten degrees above normal for temperatures for much of October, but finally things should trend toward "normal" in the long term. Cold front will push off the coast Wednesday and an upper level trough will briefly move over the northeastern. Skies will probably see increasing cloudiness Wednesday afternoon with isolated showers as cooler air moves into the region. Highs in the lower 60s east of the mountains, 50s west. Lows at this time of year should be in the lower 40s outside of the cities, which is close to what Wednesday night will be. Temperatures west of the Blue Ridge expected to drop into the mid to upper 30s. Frost advisories may be needed Page/Warren/ Clarke/Frederick into the eastern panhandle of WV. Trough will be lifting out Thursday allowing for sunshine but cool temperatures. After that high pressure will be developing offshore while a trough moves over the upper midwest. This will palce the eastern seaboard in warmer southerly flow. By Saturday expect to see temperatures up near 70. GFS is bringing the next front into the forecast area late Saturday while the Euro is significantly slower. Will add 30 PoPs to Saturday afternoon but these may need to be removed depending on later model runs.
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&& .AVIATION /07Z SUNDAY THROUGH THURSDAY/...
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Brief patchy fog possible early this morning and again Monday morning at outlying terminals (CHO/MRB/IAD). Lower CIGS/VSBYS likely Monday night in showers as low pressure passes to the west dragging a cold front through. LLWS possible Monday night as well, along with a few gusts to 20+ kts. Conditions improve by Tuesday afternoon as winds become westerly. VFR conditions expected Wednesday and Thursday.
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&& .MARINE...
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Light winds until late Monday/Monday night in southerly channeling as low pressure develops and passes west of the waters. Gale force gusts possible, especially in heavier downpours late Monday night into Tuesday morning. Winds become west after cold front crosses Tuesday afternoon with SCA gusts possibly lingering into Wednesday.
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&& TIDES/COASTAL FLOODING: A period of southerly winds will cause anomalies to rise early this week. Minor tidal flooding is likely Monday into Tuesday before winds become west and water levels recede. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...None. && $$ PRODUCTS...DFH/WOODY!

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