9:50 AM MDT, Monday, September 7, 2020

The main change from yesterday is that the storm progression is slower, so the chance for periods of accumulating snow will likely extend well into Tuesday night. Before the cold front this evening, some hot, dry westerly winds may develop again along the foothills.

Storm progression

The strong cold front is likely to move through this evening before nightfall north of I-70, and around or after sunset as you go south. Clouds and precipitation are likely by about midnight (snow above 7500 feet) along the foothills from the western Denver suburbs northward, and spread south and east during the late night.

Rain will probably change to snow before 3 AM in Cheyenne, between 4 and 7 AM from Fort Collins to Denver, and after sunrise as you move south. Snow may be heavy at times Tuesday and become more intermittent as it continues through part or all of Tuesday night.

Peak depth in grassy areas through Tue night

Accumulation this time of year is more efficient at night, but accumulation during the day can occur quickly during periods of heavy snow, and then melting can dominate during lighter snow periods. For that reason, snow depth at the lower elevations is likely to be quite variable.

Above 8000 feet: 10-18 inches

6000-8000: 6-12 inches

Fort Collins (west side), Boulder, Broomfield, west & south sides of metro Denver, Castle Rock: 4-9″

Greeley, Fort Collins (east side), Longmont, DIA, Aurora, Colorado Springs: 1-5″

*NOTE: the official snowfall may be greater than the peak depth on the ground, especially in the lower elevations because the snow depth may increase and decrease more than once during the storm

Impact

Prepare for power outages and damage to vegetation.