Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 202007 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 307 PM EST Fri Jan 20 2017 .SYNOPSIS...
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A front will remain stalled south of the area through Saturday. Low pressure will impact the area Sunday through Monday before moving away Tuesday. A cold front will pass through the area Wednesday into Wednesday night and an upper-level trough may build overhead late next week.
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&& .NEAR TERM /THROUGH SATURDAY/...
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Warm front remains to the south at this hour though some breaks have appeared in the clouds west of the Blue Ridge. These are struggling to make it east of the mountains, however, so still think eastern areas will stay pretty cloudy tonight and at least through Saturday morning. Last showers are currently pushing northeast into the metro, then otherwise it should be dry except for patchy drizzle, through Saturday, as a weak ridge builds aloft and some drying also occurs aloft. Given the high low level moisture now present, any breaks in the clouds will allow fog to form, so have kept patchy fog in the forecast. Lows tonight should stay mild, generally in the 40s, with 50s likely on Saturday especially if we can get some breaks in the clouds.
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&& .SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
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Guidance continues to show a significant coastal storm system Sunday and Monday, though they continue to shift on the details. Today`s guidance has shifted west a bit, and somewhat weaker. Overall however, still expect rain to overspread the area Sunday with the first wave of low pressure, then another surge of rain late Sunday night or early Monday with the main center. This second, stronger low looks weaker than yesterday but still will bring some breezy conditions. A wind advisory is still not out of the question on Monday, but the odds look lower than yesterday given the weaker low and its shift westward. Generally, between the two waves of low pressure, looks like most of the region should end up with around an inch of rain, with potential for up to two inches. Given recent dry weather, this probably isn`t a big flood threat, especially given the long period over which the rain is expected to fall. Also given the shift westward on the guidance, the small threat of snow that some models showed yesterday is looking less likely today.
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&& .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
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Surface low pressure over or near our area will continue to push northeast away from our region Monday night into early Tuesday. Precipitation associated to it should be tapering off, mainly east of the Blue Ridge during this time... while higher elevations could experience different p-types Monday night. Dry conditions expected on Tuesday into Wednesday -some showers possible at higher elevations per some GEFS members- before another cold front moves through the region Wednesday night into early Thursday, with limited precipitation. Upper trough to our west will slowly move east, bringing precipitation west of the Allegheny Front Thursday into Friday. Some precipitation could reach east of the Blue Ridge Thursday night into Friday, but still highly uncertain if it will, and what p-type. High temperatures will be in the 40s and 50s Tuesday and Wednesday, decreasing into the 30s and 40s on Thursday and Friday. Low temperatures will be in the 30s and 40s, with Thursday night being the coldest.
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&& .AVIATION /20Z FRIDAY THROUGH WEDNESDAY/...
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Very tricky aviation forecast. Guidance has grossly overdone moisture today, so cigs and vis have generally verified significantly less restrictive than expected. That having been said, there are still some IFR cigs out there and these may continue to affect terminals tonight into Saturday. There is potential that the clearing west of the Blue Ridge may expand eastward this evening, but this may open the window for fog. Winds should remain light through Saturday night. Cig/vis should improve Saturday afternoon, but rain moving in late Saturday night will cause restrictions to return for Sunday and Monday. Winds will also likely start getting gusty by Sunday night and Monday, generally from a northeast direction. Low pressure system will move away Monday night into early Tuesday and precipitation will be tapering off during this time. Breezy conditions expected, with wind gusts reaching 20 kts... decreasing into Tuesday night. Dry conditions expected Tuesday into Wednesday. Some showers possible Wednesday night. So, sub-VFR conditions possible Monday night into Tuesday, becoming VFR sometime Tuesday and remain into Wednesday.
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&& .MARINE...
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Sub-SCA conditions through Saturday night with southerly winds tonight, gradually turning southeasterly on Saturday. Winds increase markedly for Sunday and Sunday night out of the east/northeast with Small Craft Advisory conditions likely Sunday, with Gales possible Sunday night. Low pressure system will move away Monday night into early Tuesday and precipitation will be tapering off during this time. Breezy conditions expected, with wind gusts reaching 20 kts... decreasing into Tuesday night. Dry conditions expected Tuesday into Wednesday. Some showers possible Wednesday night. Small craft advisory expected for Monday night into Tuesday night as winds diminish below the threshold.
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&& .TIDES/COASTAL FLOODING...
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Onshore flow will strengthen later Sunday through Monday as a coastal storm moves northward into the area. Tidal flooding is possible during this time. The flow will turn offshore later Monday night and Tuesday as the storm moves away.
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&& .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...None. && $$ SYNOPSIS...RCM NEAR TERM...RCM SHORT TERM...RCM LONG TERM...IMR AVIATION...IMR/RCM MARINE...IMR/RCM TIDES/COASTAL FLOODING...RCM

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