* Winter weather advisory for Loudoun, Frederick and Carroll counties through this 8 p.m. this evening *

UPDATE, 11:30 a.m.: The National Weather Service has posted a winter weather advisory for up to 1” of snow and sleet in Loudoun, Frederick and Carroll counties.

From earlier: A weak weather system coming up from the southwest has already produced a mix of snow, sleet and rain in central Virginia. This area of mixed precipitation should reach the Washington, D.C. metro area this afternoon.

In Charlottesville, precipitation has been a mix of snow, sleet and rain. Sleet is falling in Stafford county and around Fredericksburg. When the batch of precipitation reaches the D.C. area, we’ll likely see a variety of precipitation types with snow and sleet favored north and west of the beltway, a mix of snow, sleet and rain inside the beltway, and rain and sleet south and east of the beltway (maybe mixing with snow).

For large parts of the metro area, precipitation may change back and forth between rain, sleet, and snow, whereas for places like Leesburg and Frederick, snow may well dominate.

The bottom line is this: areas north and west of the beltway have the best chance of seeing snow whiten the ground. We can’t rule out this happening inside the beltway too....but with temperatures already climbing through the 30s, it’s going to be difficult for snow to sustain itself. As you head into northwest Montgomery county, Loudoun and Frederick county, a coating to an inch or so is possible, and even a bit more at elevations above 1,000 feet (up to 2 inches or so).

Any snow accumulation is most likely on grassy areas. Roads probably remain wet except if/when snow falls heavily and/or at high elevations. Any slicks spot in areas that get snow/sleet are most likely after around 4 p.m. when the sun starts to go down.

Because temperatures are so marginal for snowfall, there is some risk that the balance of precipitation is rain and sleet, especially inside the beltway and to the southeast.

For most of the area, this mixed precipitation lasts around 6 hours, starting within an hour or two of 1 p.m. and ending within an hour or two of 7 p.m. (early side of window to southwest, and later to the northeast).

This is a very tricky event, but we feel confident that at least parts of the area will have some ambiance snow falling this Christmas Eve.