After a mild autumn across most of the U.S., a dome of Arctic air is sliding south across the Mountain West and Great Plains. Devoid of potent storm dynamics, the front is primarily bringing a dramatic drop in temperatures and producing rather light precipitation, in the form of snow, sleet or freezing rain.
Here in Metro Denver, the Arctic air mass arrived overnight and our morning low sits at 15 degrees F; light, powdery snow is falling and three inches now coat our Littleton farm (more is expected through the day). Further south, in the Four Corners region, low pressure will inject Pacific moisture into this frigid, polar air, producing heavy snow accumulations across the Colorado Plateau and San Juan Mountains.
Since the jet stream has dipped far to the south, the dome of dense Arctic air is free to drift downhill and with thus spread southeastward over the next few days. In concert, a southerly flow will redevelop along the Front Range and a rapid rebound to seasonal conditions is anticipated; unfortunately, I will depart for Missouri tomorrow, following winter's slide across the Great Plains.