Light wintry mix possible early Friday

Even though we may flirt with 60 this weekend, Arctic air seldom departs without a little drama. A weak weather system could lay down a little light frozen precipitation early Friday morning…especially for our colder northern and western suburbs.

Frozen precipitation is by no means a guarantee. Some models simulate little to no precipitation. But some moisture will be streaming into the region from the southwest while  stale cold air lingers – especially close to the ground. That leaves open the possibility for light freezing rain.

This event may resemble Sunday’s freezing raining event to a degree. It’s a similar set up with overrunning precipitation and departing cold air. On Sunday, the colder north and west suburbs out towards Frederick and Loudoun counties experienced the worst conditions. I would expect a similar deal this time, although precipitation amounts should be lighter overall and the cold air should erode slightly faster (but may hold on longer than models predict from Ashburn to Frederick and to the west).

The GFS model, shown below, simulates a light period of freezing rain early Friday morning – mainly from the District south – before temperatures warm above freezing and precipitation departs).


GFS model showing accumulated precipitation through 7 a.m. Friday morning. Blue line is the freezing line. (WeatherBell.com)

(The European model, not shown, is similar).

In contrast, the NAM model shows the precipitation bypassing the immediate D.C. area, but clipping our colder north and northwest suburbs with a brief period of frozen precipitation which could start as snow before becoming a wintry mix.


NAM model showing accumulated precipitation through 7 a.m. Friday morning. Dark blue line is the freezing line. (StormVistaWxModels.com)

We’ll keep on eye on this little system. Right now, my forecast would be a 50 percent chance of freezing rain (possibly starting as snow and/or sleet, especially north and west of town), gradually changing to plain rain – with the longest duration of frozen precipitation in our colder suburbs. Like last Sunday’s event, just a little freezing rain can cause problems. Moreover, the stakes are a bit higher this time being a school and work day.

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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