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Posted at 11:18 AM ET, 01/20/2012

Winter weather mess: snow, sleet, ice overnight into Saturday around Washington, D.C.


Snow accumulation potential before changeover to ice and/or rain

* Winter weather advisory issued for entire metro region & frequent questions *

Cold, dry Arctic air seeps into the region today while an area of storminess approaches from the southwest. The cold air and storminess collide tonight, delivering a frozen, wintry punch to the metro region.

Precipitation likely begins as a period of snow (except well south of Washington), before transitioning to sleet and freezing rain and plain rain in some areas. The most significant snow and ice accumulation is expected in the region’s north and west suburbs.

This storm will have the most widespread impacts of any winter weather event this season. Early Saturday morning, much of the region will contend with slick travel, especially on untreated roads, ramps, bridges, and overpasses. From western Montgomery county, eastern Loudoun county and to the northwest, temperatures may remain below freezing all day Saturday, and significant icing is possible, and even power outages.

These impacts will be somewhat mitigated by the late Friday night and Saturday timing of the storm, conveniently avoiding rush hour commute and most school operations.

Continue reading for a storm timeline and zone map.

TIMELINE

Through 10 p.m. tonight: Conditions mostly dry, clouds increase. Temperatures falling below freezing.

10 p.m. - 1 a.m. tonight: Snow and sleet developing from southwest to northeast, except sleet and freezing rain south of Prince William county . Light snow accumulations possible, especially north and northwest of D.C. Temperatures 25-30

1 a.m. - 4 a.m.: Snow and sleet transition to sleet and freezing rain, except from Baltimore and Frederick and points north where snow and sleet continue. Temperatures 25-30, northwest to southeast.

4 a.m. - 7 a.m.: Sleet and freezing most locations in metro region. Temperatures 26-32, northwest to southeast

7 a.m. - 10 a.m.: Sleet and freezing rain, possibly changing to plain rain from District and south and east. Temperatures 27-34, northwest to southeast.

10 a.m. - 1 p.m.: Freezing rain north and west of the beltway, rain or freezing rain to the south and east. Temperatures 29-35, northwest to southeast

1 p.m. - 4 p.m.: Precipitation tapers off from southwest to northeast. Temperatures 30-35, northwest to southeast.

ZONE SUMMARY


Zone 1: Little or no snow accumulation. Light freezing rain accumulation possible by Saturday sunrise, then plain rain. Slick travel probably limited to early morning hours.

StormCast

Zone 2: A little snow possible, probably a coating to half inch or so in the northern half of the zone, then mainly sleet and freezing rain (up to 0.1” - a thin glaze). Precipitation may change to plain rain between 7 and 10 a.m. Saturday morning, but there may well be some areas on the north and west end of this zone that struggle to rise above freezing. Some slick travel possible through late morning.

StormCast

Zone 3: Up to an inch or so of snow/sleet accumulation is possible through 1 or 2 a.m. before the transition to ice. 1-2” of snow is possible in the northern half of the zone, probably not much snow towards the south in Fauquier county. Icy conditions (0.1-0.2” of ice) are possible through mid-morning, and possibly longer in the colder north and west sections of this zone - which may hold near freezing much of the day. Slick travel possible through late morning, or even a bit later, especially on untreated roads.

StormCast

Zone 4: 1-2 inches of snow is possible before the transition to ice between 2 and 5 a.m. Significant ice accumulation (0.2” or more) is likely on top of the snow, and isolated power outages cannot be ruled out due to ice accretion on trees and power lines. This is a significant winter storm for this zone, with temperatures likely holding below freezing all day. Widespread hazardous road conditions are possible.

By  |  11:18 AM ET, 01/20/2012

Categories:  Latest, Winter Storms

 
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