Drastic weather changes just around the corner
As we’ve been discussing here the door to the Arctic air banked up over Canada is just about to open for the first time this winter. Enjoy today’s (Sunday’s) high temperature in the lower 50s because we won’t see that mark again for a while. This afternoon the first cold front will pass through with little fanfare other than a shift in the wind direction around to the northwest and wind gusts up to 25 mph or so. This sets the stage for a much more active weather scene on Martin Luther King day as shown here in this HPC graphic of the surface cold front positions Monday morning at 7 a.m.:
Between the first cold front shown over the southeastern U.S. and the Arctic front approaching from the northwest the surface winds over the ‘Burg will shift around to the south and southeast. This will usher in low level moisture while a lee trough forms east of the Blue Ridge over the Virginia Piedmont. This feature often sets the stage for thunderstorms during the spring and summer months, but in this instance cold Arctic air will be pushing over top of the relatively warm moist air at the surface to create instability while the lee trough provides a “lifting mechanism” that will trigger convection. The result will be scattered snow squalls over Northern Virginia, each of which will provide windy and furious snowfall for a few minutes. The scattered nature of these squalls are what has led the National Weather Service to only predict a 30% chance for the ‘Burg Monday and Monday night, but if one hits your backyard the ground could very well whiten quickly.
The story for the middle part of next week will then be the cold. Given the strength of this very cold and very dry air mass the ‘Burg may very well not see temperatures climb much above the freezing mark – even during the daylight hours – starting Monday night through Thursday night. That, coupled with the winds and very dry air, will lead to the need for parkas, mittens, scarves, and perhaps some lotion for dry skin this week. The wind chills will be noteworthy!
It looks like this very cold shot will be followed by a brief warmup and then another cold shot next weekend. In between there is the potential for a substantial low pressure system to affect the area Friday, but it’s too early to tell exactly what that storm might bring to the ‘Burg. Meanwhile the pattern of Arctic air outbreaks followed by brief warmups may continue for at least a couple of weeks so keep the warm clothes handy.