Wintry slop moves in this evening and overnight; light accumulations possible

* Winter Weather Advisory for Frederick, Loudoun and northern Fauquier counties midnight to 6 a.m. Monday *


Radar & lightning:Latest regional radar shows movement of precipitation and lightning strikes over past two hours. Refresh page to update. Click here or on image to enlarge. Or see radar bigger on our Weather Wall.

Wintry precipitation is on the approach (snow falling in Blacksburg, Roanoke and near Charlottesville) and should reach the Washington, D.C. metro region late this afternoon into this evening.  A mix of rain and snow should change to a period of snow for most of us tonight with many of us waking up to at least a white coating on grassy areas by morning.  Accumulations on road surfaces are most likely in colder north and west suburbs with more elevation.

Accumulation potential

Capital Weather Gang winter weather expert Wes Junker sums up for areas within a one county radius of the District:

Temperatures are expected to remain above freezing near  the city through the event but may hover close enough to freezing early Monday morning before sunrise to allow some light accumulations on grass providing the precipitation rates are high enough.  That remains a big if.  If rates are high enough there could be accumulations of a sloppy inch or two in the suburbs west and north of the city with an inch or less in the city.  After the sun comes up on Monday, snow will have a hard time accumulating and should gradually mix with and change to rain.

From northern Fauquier county through central Loudoun county and into central and western Frederick county, accumulating snow of at least 1-3 inches is likely, with higher amounts of 3-6 inches or so possible at elevations above 1,000 feet.

Boom potential: If temperatures are on the low side and precipitation is on the heavy side of forecasts, amounts of  2-4 inches could be realized even inside the Beltway (still mostly on grassy areas but a little on roads possible during heavier bursts) with 3-6 inches west and north of the beltway, and even 6 inches or more in some of the elevated areas west of Leesburg and Frederick. (20-30 percent chance)

Bust potential: If temperatures are on the warm side of forecasts (generally above freezing) and precipitation is lighter, no snow would likely accumulate inside the beltway with perhaps just a dusting immediately north and west, and an inch or two in colder areas around Leesburg and Frederick. (30 percent chance).

The map below summarizes our general accumulation forecast, and is a pilot of our new approach to snow accumulation maps in the wake of Snowquester. Note the confidence levels and probabilities for “boom” (more snow than forecast) and “bust” (less snow than forecast) scenarios…

CWG's snow accumulation forecast for late Sunday through Monday afternoon. "Boom" indicates probability of more snow than predicted. "Bust" indicates probability of less snow than predicted.
CWG’s snow accumulation forecast for late Sunday through Monday afternoon. “Boom” indicates probability of more snow than predicted. “Bust” indicates probability of less snow than predicted.

Timeline

3 p.m. – 7 p.m. (Sunday): A mix of precipitation moves into areas from southwest to northeast. Temps 37-43.

7 p.m. (Sunday) – 1 a.m. (Monday): Mixed precipitation transition to snow, except perhaps remaining a rain/snow mix east of I-95. Temps 33-38.

1 a.m. – 7 a.m. (Monday): Snow, with some accumulations possible, mainly north and west of the city on grassy areas. Temps 31-35.

7 a.m. to 1 p.m. (Monday): Snow, mixing with and possibly changing to rain.  Little additional accumulation after 9 a.m. Temps 32-37.

1 p.m. to 7 p.m. (Monday): Mixed rain and snow changing to light rain/drizzle, and ending. Temps 35-40.

SchoolCast





Alexandria/Arlington/District and points east:





Montgomery/Howard/Fairfax/Prince William/Stafford counties:





Loudoun/Fauquier/Frederick counties:





FedCast:

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Jason is currently the Washington Post’s weather editor. A native Washingtonian, Jason has been a weather enthusiast since age 10.
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