Noon MST, Wednesday, December 20, 2017
First, the one important change from my weather update yesterday morning is that the cold snap for the weekend is looking less intense and less prolonged than what I was thinking yesterday. But you should still expect colder weather with a couple periods of snow Thursday and Saturday. Monday (Christmas) is rather uncertain at this point but the trend has been toward dry and not so cold.
Thursday cold front and snow
A weakening storm system moving through southern Colorado Thursday should still be strong enough for some snow accumulation, mainly in the morning and mainly in and near the foothills. Temperatures should be well below freezing all day and snow may be underway in and near the foothills from Denver north by daybreak. Snow will probably become intermittent and end along the northern Front Range by early afternoon; early evening south of Denver.
2-4 inches: in and near the foothills (Cheyenne, Boulder, western Denver suburbs, and Castle Rock).
trace-2 inches: Fort Collins Longmont, eastern metro Denver, Colorado Springs.
Friday: dry with temperatures rising to near or a little above freezing in the low elevations after a very cold morning.
The next cold front on Saturday will keep temperatures in the teens (or drop them into the teens if the front doesn’t arrive until late morning), and then into the single digits for many locations at night. Minor accumulation of snow appears probable along the Front Range.
Sunday will probably be dry and cold, but the cold air mass may be easing up during the day.
Christmas Day is an interesting forecast. A reinforcing cold air mass will likely move south into the north-central U.S. and could slip into eastern Colorado. But it may be fighting against a milder airmass pushing in from the west. Right now it appears the dry and somewhat milder weather might win out, maybe even with some Chinook wind. But that forecast could change dramatically, so I’ll update toward the end of the week.