1/4: Very Cold Temperatures on the Way This Week; Watching Alberta Clipper for Tuesday

Sunday, January 4th 5pm

I knew today would be warm, but didn't think it'd be quite this warm...highs generally made it into the low to mid 60s across the entire Shenandoah Valley (even low to mid 70s across far SE Virginia!).  Big time changes on the way this week after the passage this evening's cold front.

Highlights:

• The Cold: This will definitely be the big story.  After today, we won't see temperatures above 40 the rest of the week.  A strong Canadian high will build down across the central portion of the country and eventually work into the east.  Wednesday and Thursday will be our coldest days with highs potentially stuck in the low to mid 20s.  We'll have a few nights of lows all the way down into the teens and even single digits.  With blustery conditions expected, prepare for wind chills down below zero.  It'd be a good idea to start making preparations to minimize bus stop wait times, bring in outdoor pets, protect against frozen pipes, etc.  

Departure from Average Temperatures Thursday... 15-20 degrees below average across the East

• Clippers: While not expecting any big storm system to meet up with this cold air, we will have clipper potential...the first on Tuesday and the second potentially Thursday night into Friday (The 2nd doesn't look to have much impact here..too far north...but will be keeping an eye on any change in track).  The first will be a pretty vigorous shortwave diving out of Alberta and across the northern plains before swinging east across the northern mid-Atlantic.  Usually for us to maximize the amount of clipper precipitation that crosses the mountains, we need the vorticity maximum (big black X on image below) to pass just to our south which doesn't look to be the case here. 

Vorticity Max with Alberta Clipper System Early this Week

With that said, it's still worth watching for a bit of light snow Tuesday...especially across the northern Valley area closer to the vort. max and western facing slopes where some upslope component will come into play.  Once again, nothing big...but wouldn't surprise me if someone squeezed out an inch or so, with a bit more up towards the Mason Dixon line.  The trend of the day has been to nudge this system south a bit so will be watching to see if that continues tonight.

Surface Reflectivity Tuesday AM