3:55 PM, Sunday, December 4, 2016
The beginnings of a cold few days will start Monday afternoon, and then very cold with some snow likely Tuesday afternoon into Wednesday.
It may still be rather mild Monday morning, but don’t be fooled. A cold front will move down the Front Range from Cheyenne to Colorado Springs and temperatures will fall and not likely reach above freezing again until late in the week. Temperatures on Tuesday will likely not get out of the 20s even in the lower elevations, and it may start turning even colder by afternoon. Wednesday will likely stay below 20 at all elevations.
Wednesday and Thursday mornings will be very cold with single digits Wednesday and around zero on Thursday in the lower elevations. If we get clear skies over fresh snow cover Thursday morning I would expect to see many locations slip below zero. At the Boulder climate station +3 on January 1st is the coldest so far in 2016 (an atypically warm reading for an annual low), so we may get a more typical annual min yet!
Some scattered light snow may accompany the first push of cold air late Monday into Tuesday with light accumulations in the mountains and little or nothing in the lower foothills and plains. This is the kind of setup that sometimes leads to freezing drizzle along the Front Range, but with low moisture values across the high plains we may be on the edge of forming freezing drizzle and fog.
The second push of colder air will be accompanied by Pacific moisture in the mid levels and maybe deeper upslope too. So snow is likely late Tuesday into early Wednesday. At this time it looks like relatively light amounts, 2-5 inches, probably topping 6 in a few locations in the mountains. I will be watching for the small possibility that a mid level circulation will develop and increase the snow potential, but that does not appear likely right now.