Summary:

Significant precipitation will fall over most of Colorado from Thursday midday through Friday with snow accumulating over 10,000. Mountains that are along and east of the divide will see the heaviest snow with amounts over 10 inches for elevations above 11,000-12,000ft. After the storm, Saturday will dry out and be sunny, then a colder storm will bring 5-7 inches of snow for the northern half of the state on Sunday. Most of next week should be dry.

Details:

Here we go! There are two storms to talk about over the next four days, with some hefty snow amounts possible from each system.

The first storm will move through Colorado on Thursday and Friday. This storm is what's left over from Hurricane Simon, so it will bring LOTS of moisture and relatively warm air (ie. high snow levels).

Snow and rain showers will cover the state on Thursday, likely reach peak intensity on Thursday night into Friday morning, and then linger through the day on Friday. You're not going to see a lot of sun for the next two days.

For snowfall, the heaviest amounts will be on mountains over 12,000ft (flakes will accumulate down to 10,000ft). As for locations, since the system will generally bring winds from the south, southeast, and east, the mountains favored by these directions will be Wolf Creek, Monarch, the Sangre de Cristo Range and Wet Mountains in southeast Colorado, the Collegiate Peaks near Buena Vista, and the Front Range mountains from Mt Evans north to Berthoud Pass and the Indian Peaks. The areas that I mentioned above could see double-digit snowfall totals by Friday evening, and again, the deepest accumulations will generally be found above the elevations of most mountain passes. Rocky Mountain National Park is often favored by east winds, but I'm not sure the heaviest precipitation will make it that far north

The map below is the snow forecast for Thursday and Friday from the National Weather Service, and it looks about right to me.

The other component of storm #1 will be the rain. For locations in southern and eastern Colorado that are below 9,000ft, the precipitation will generally be in the form of rain and not snow. Some areas could see 1-3 inches of rain with most models showing the heaviest rain falling south of Denver. Yesterday some models pushed this heavy rain as far north as Boulder and Ft. Collins, but by this morning the models trended back south. In summary, most areas will see rain with the largest totals south of Denver and along / east of the mountains.

The map below, from Weatherbell.com, shows the precipitation forecast for Thursday and Friday from the high resolution NAM4km model (rain and melted snow). Amounts of 1-3 inches are large for Colorado, especially in October which is usually a drier month east of the mountains.

Following this storm, clouds should slowly clear over western Colorado on Friday evening, then most of Colorado will see a sunny day on Saturday.

On Sunday, the second storm will move through bringing snow to most central and northern mountains starting around daybreak and continuing into Sunday evening. Amounts would be enough for a mid-winter powder day with about 5-7 for many mountains, and the snow level will likely dip down to 8,000ft by the end of the storm. 

Monday will start with a few lingering clouds and snow showers, then should turn out sunny and the rest of next week should follow that trend with sunny and dry weather. A few storms will push through the northwestern states next week and we may be brushed by one of these systems, but most of the action will stay in Oregon, Washington, and British Columbia.

JOEL GRATZ