Such events distort the polar vortex, which causes Arctic air to descend into the U.S. and causes temperatures to plummet.

We will spend the entire day Friday below freezing with highs in the 20s throughout most of Massachusetts.

The brutal cold will continue with temperatures Monday night as much as 20 degrees below normal, forecasters say.

At 3:26 a.m. on Thursday, the NWS Blacksburg VA issued a winter weather advisory valid for Friday between midnight and 7 p.m. The advisory is for Surry, Stokes, Rockingham, Caswell, Wilkes and Yadkin counties.

An updated winter weather advisory was released by the NWS Blacksburg VA on Friday at 6:40 p.m. in effect until Saturday at 8 a.m. The advisory is for Stokes, Rockingham and Caswell counties.

A cold weather advisory was issued by the NWS San Francisco CA on Wednesday at 5:46 p.m. valid for Thursday between midnight and 8 a.m. for Southern Salinas Valley/Arroyo Seco and Lake San Antonio and Monterey County.

If you're heading out, brace yourself—it's the coldest day of the season.

Below-freezing temperatures are forecast for Denver until about 11 a.m. Thursday, according to the NNWS. Until then, ice will remain on roads throughout the Denver area.

The two periods of light snow also will affect two different areas. The first snow shower burst will roll across northern Lower Michigan and the Upper Peninsula Friday night into Saturday morning. This snow should just be a very spotty light snow as it moves into southern Michigan. I would say it runs out of gas heading south.