Following another round of snow, making Green Country white, Arctic air is plunging into the state. This is a super-charged Arctic air mass as the core of cold air is actually totally displaced from above the Arctic Circle to the Midwest! This is an historic cold spell and the most dangerous aspect of this winter storm.
We should feel fortunate that this is just a glancing blow. Wind chill values over the Upper Midwest will range from -40 to -60 degrees from now through Monday evening! I can't even fathom what that would feel like. It shouldn't downplay what we're experiencing here though. With a snow pack of 1" to locally 5" in northeastern Oklahoma (see first map), and strong advection of cold air from the Arctic, our temperatures will dip to near or below 0°. When you factor in even a modest breeze, it will feel like -10° to -20°! It hasn't been that cold here since after the blizzard of 2011! The second map shows projected wind chill values at 7am Monday.
In case you wonder how we calculate a wind chill, the third image I've attached is a chart on how we correlate temperature and wind. It's rare that we ever see wind chill readings dip much below 0° and especially to the range where frostbite occurs in 30 minutes or less to exposed skin. Ouch!
The good news in all of this is that it's a brief cold spell. Harsh, but fairly short-lived. Our wind will die off Monday evening and switch from the northwest to southwest by Tuesday morning. This begins our warming trend, which will allow ice and snow on roadways to melt by midday Tuesday. It will be a welcome thaw indeed. A chance of rain is back Wednesday as a fast-moving upper-level wave comes in. That will help to further melt the snow, but we may be cold enough for a transition to a light wintry mix again Wednesday night – stay tuned.