Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 151854 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 254 PM EDT Sun Oct 15 2017 .SYNOPSIS...
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A cold front will push into the Mid Atlantic tonight followed by a return to high pressure early in the week and hold through the end of the week.
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&& .NEAR TERM /THROUGH TONIGHT/...
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Low clouds have been frustratingly slow to clear in the Baltimore-Washington corridor today. Evidently, the inversion has been strong enough to trap low-level moisture, with the mixing winds merely overriding the top of the saturated layer. We still have broken clouds from GAI-DCA northeast as of 230 pm. Am hopeful that these clouds will erode in the 4-5pm window if not before. The band of incoming precipitation has been thin, and is not close to the forecast area...emerging off Lake Erie at this time. Guidance has been backing off PoPs through the rest of today, and have been following suit. While low-level convergence and 850 mb thermal forcing good, these features outrun the upper level support. As a result, mesoscale guidance all depict a rapid weakening as soon as the line hits the Appalachians. Regardless, the best chance will come in the night time hours... Blue Ridge/Catoctins west at or before midnight, east of there overnight. Am keeping this as chance PoPs for most places, but there could be local enhancement as this line approaches southern Maryland early Monday morning.
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&& .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
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The front will be clearing the area Monday morning. Based on current extent and speed, there could be some lingering showers east of I-95 early. Otherwise, the day will be marked by clearing skies and increasing winds due to a surge of cold advection. Gusts to 20-25 mph seem likely. Temperatures may not be purely diurnal, but advection and compression may balance out during the afternoon. High pressure will be building over the area Monday night through Tuesday night. If winds decouple quick enough early Tuesday morning, frost would be possible as radiational cooling conditions should be otherwise nearly ideal. Have added it to the HWO. Tuesday night into Wednesday morning would also have that potential.
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&& .LONG TERM /WEDNESDAY THROUGH SUNDAY/...
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Dry weather conditions are expected in the long term period as surface high pressure is centered near or over our area between Wednesday and Sunday. At the upper levels, ridge will be amplifying and building over our region Thursday night and remain into Sunday. High temperatures will above normal, and will be gradually increasing from the 60s and low 70s on Wednesday to upper 70s/near 80 on Sunday.
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&& .AVIATION /19Z SUNDAY THROUGH FRIDAY/...
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Low clouds have been frustratingly slow to clear in the Baltimore-Washington corridor today. MVFR conditions linger across DCA/BWI/MTN; these should erode 19-21 UTC. As soon as clouds do break up, gusty winds will commence...up to 20 kt. A cold front will cross the terminals tonight. Precipitation should be scattered and brief. Restrictions unlikely. The wind shift will be the most notable item, within a few hours of midnight. A period of VFR clouds (cigs 040-050) will also transpire. Northwest winds will gust to 20-25 kt on Monday. Winds will diminish Monday afternoon-evening. Otherwise VFR through Friday.
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&& .MARINE...
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Persistent low clouds have been hindering good mixing, but 20 kt winds have been present and have been punching through on brief/random occasions. Clouds beginning to break apart. Small Craft threshold gusts should become more common. Likely will have a lull this evening as a cold front approaches the area. But, after frontal passage, which will be pre-dawn, a surge of northwest winds will have good momentum transfer potential. Will keep a Small Craft Advisory for all waters through Monday, and then end in a staggered fashion during Monday night. Winds will be lighter for the rest of the week as high pressure crests overhead.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...None. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory until 2 AM EDT Tuesday for ANZ531>533- 539>542. Small Craft Advisory until 6 PM EDT Monday for ANZ530-535-536- 538. Small Craft Advisory until 6 AM EDT Tuesday for ANZ534-537-543.
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&& $$ SYNOPSIS...HTS NEAR TERM...HTS SHORT TERM...HTS LONG TERM...IMR AVIATION...HTS MARINE...HTS

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