12:15 PM MDT, Friday, October 25, 2019
Enjoy the mild autumn weather today and Saturday. A cold front Saturday evening (maybe afternoon in Cheyenne) is expected to begin a 4 or 5-day period with much below average temperatures. Significant snow is likely Saturday night through Monday morning, with perhaps another period of snow on Tuesday as an even colder air mass arrives.
The first period of snow is likely to spread north-to-south from Cheyenne to Colorado Springs Saturday evening and night, and continue until late Sunday night or Monday morning. It appears that there can be periods of moderate or heavy snow alternating with periods of lull in the action. Most likely accumulations through Monday morning:
8-14 inches in the mountains from Rocky Mountain Park south through the Pikes Peak region, and in the Palmer Divide region.
6-10 inches: Denver (south and west sides), Broomfield, Boulder, Cheyenne
2-5 inches: DIA, Longmont, Fort Collins, Colorado Springs
I will update these numbers tomorrow if necessary. Additional snow is possible on Tuesday.
Sunday and Monday in Denver-Boulder are likely to stay below freezing during the day with teens on Monday morning (assuming cloud cover does not let it get colder). An even colder air mass on Tuesday should result in temperatures barely making to 20s, and falling to the single digits at night. The record low on Tuesday for both Denver and Boulder is -2 (the October record) and that will likely stand. On Wednesday we have a shot at a record if skies clear out Tuesday night. The record for Wednesday in Denver is +7 (1991) and for Boulder it is +6 (1993).
There is some disagreement in weather models about how quickly this very cold air mass will release its grip. Some have milder weather starting to return on Halloween while others keep it quite cold until then.