With strong northwesterly winds blowing, wind chills will be near zero during the day Thursday and may be as low as -10 to -15 Thursday night and Friday morning along mountain ridges. Winds N 5-15, gusting to 20 miles per hour. The kicker overnight is that some patchy drizzle will be possible in addition to those freezing temperatures.
This is unsafe cold, the likes of which we haven't seen since late February of 2015. Highs will stay in the upper teens and lower 20s.
WHAT WE'RE LOOKING INTOThe cold air and snow showers will stick around into Thursday night.
Then Winter Storm Decima coming from out of the western states will leave a swath of accumulating snow through the northern Plains, upper Mississippi Valley, Great Lakes and parts of the Northeast late this week into the weekend. Our color charts don't even go colder than that. Chicago has a chance to see its first subzero temperature in December since 2013, while Pittsburgh may record its first December single digit low since 2009. This means serious wind and chill.
There is a chance for a messy mix Saturday.
A warm front will push through Saturday morning with a band of snow. Also keep in mind, the warmer temperatures and steady rain will likely wash/melt a lot of that snow away through Saturday afternoon, so we wouldn't face a potential half-foot of snow for long anyway. For Sunday, we trend even warmer as some towns could hit the 50s for highs, but it will be soggy as rain continues.
Thereafter, the second cold front moves through, unleashing super cold air into the region.
Because systems are moving rather fast the winds should weaken Friday afternoon and diminish Friday evening. I wouldn't rule out some light snow shower activity on the backside of the rain and the front, as temperatures begin to drop again. Aside from some eroding clouds Wednesday morning and a few more clouds Wednesday afternoon, sunshine should dominate the sky.