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Posted at 09:06 PM ET, 03/17/2013

Chance of snow/mix for Monday morning commute; most likely impact west of D.C. Beltway

* Winter weather advisory N and W of D.C. midnight to 2 p.m. Monday | Winter storm warning western Va., mountains (map) *

Cold air has seeped into the region today setting the stage for some messy weather late tonight into Monday morning as a wave of low pressure approaches. West and northwest of the beltway, a light accumulation of snow (one to perhaps two inches) is possible. Little accumulation is expected inside the beltway and to the east and southeast where more of a mix of precipitation is favored.

In short, the same areas that got accumulating snow during the Snowquester (or Noquester) are those most likely to get a bit of accumulating snow from this event (though overall amounts should be less in most areas).

Link: Snow accumulation map from National Weather Service (we concur with this, but favor the lower end of the given ranges, generally.)

Key points

* The steadiest precipitation should fall between around 2 a.m. and 8 a.m. In the District and points south and east precipitation may begin as rain before changing to mixed precipitation and/or snow. In the colder suburbs to west and northwest, mixed precipitation and snow are more likely.

* Generally, precipitation amounts should be light, but a period of moderate, accumulating snow is possible towards dawn, especially west of the beltway and into western Virginia.

* Any snow accumulation (if it occurs), especially at lower elevations and within the immediate metro region, would occur mainly on grassy areas, car tops, mulch, etc. Road temperatures are fairly warm.

* Some snow accumulation is *possible* on roads in western Fairfax county, the northwest half of Montgomery county, west Howard county, and especially into northern Fauquier, Loudoun and Frederick counties. Even though road temperatures are warm, temperatures in these areas may fall to freezing or a degree or two below and, as the precipitation will be falling when it’s dark, some sticking is possible.

* The higher your elevation and farther west you go, the more snow you will get. Winter storm warnings are out for the western Virginia, including places like Front Royal, Winchester, Charlottesville and Harrisonburg, where several inches are possible.

* Like the Snowquester storm, the I-95 corridor is in that tricky transition zone where just a couple degrees could make a big difference. Interestingly, the modeled temperatures are a little colder for this storm compared to the Snowquester in D.C. proper. On the other hand, there will be less precipitation overall.

* Mixed precipitation and snow should gradually change to rain and drizzle between around 8 a.m. to noon from southeast to northwest. Even after precipitation changes over to liquid form, it will remain cold and raw, with many locations struggling to reach 40 degrees Monday.

* This is just a *medium confidence* forecast given the rain-snow line issue and generally light, patchy nature of incoming precipitation. So everyone is aware of the range of possibilities, please consider these probabilities:

For locations inside the beltway, including the District:, and east/south

No snow: 20 percent

Snow falls but doesn’t stick except for a coating on the grass: 40 percent

1 inch of snow, mainly on grassy areas: 25 percent

1-2+ inches of snow, mainly on grass, but some on roads: 15 percent

For locations north and west of District under winter weather advisory

No snow: 10 percent

Snow falls but doesn’t stick except for a coating on the grass: 30 percent

1 inch of snow, mainly on grassy areas: 35 percent

1-3+ inches of snow, mainly on grass, but some on roads: 25 percent

SchoolCast

D.C., Arlington, Alexandria, Prince George’s County, Charles, Calvert, St. Mary’s counties:

Fairfax, Howard, Anne Arundel, Montgomery, Prince William and Stafford counties:

Loudoun, Frederick, Fauquier counties:

FedCast

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By  |  09:06 PM ET, 03/17/2013

Categories:  Latest, Winter Storms

 
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