A massive pool of Arctic air is plunging south through the Great Plains. Triggered by a broad dip in the jet stream (an atmospheric trough), the dense, frigid air is sliding down along the Front Range and will soon encompass much of the Central and Eastern U.S., from the Northern Plains to North Texas and from the Rockies to New England.
Dropping afternoon highs into the teens or single digits (F) and overnight lows below zero, the Arctic dome will produce snow (and regional blizzards) along its leading edge as it interacts with warmer, more humid air to its south and east. After an exceptionally warm autumn across most of the country, the frigid air will feel even colder and offer a blunt reminder that weather patterns can shift dramatically; though our climate is clearly warming, the seasons continue to unfold.
While these Arctic fronts often produce an upslope flow along the Colorado Front Range, resulting in snow and very low temperatures, the dense air tends to slide toward lower elevations of the Great Plains and Midwest, sparing the urban corridor from a prolonged period of severe cold. In addition, as the Arctic dome shifts eastward, downsloping, southwest winds often develop on the east flank of the Continental Divide; these chinook winds rapidly warm the Front Range cities, bringing seasonal conditions back to the region.