Initial rain/snow map for the Tue-Thu storm system

10/12/26 8:30pm: Hi, hope you are having a good Monday evening. My initial rain and snowfall forecast map below for the approaching storm system but just know this is another complicated forecast and the uncertainty in the details is high.

Even though the models agree for the most part on the upper-level low track, they can't agree on some important details like how strong the low will be (it is forecast to weaken slowly), how cold it will be as the low moves over CO, what the wind-flow will be in spots (looks to be sporadic wind-directions) and also really where the best lift and convergence will be...and hence they can't agree on rain/snow amounts in spots.

For example for Wolf Creek models show anywhere from 1.00" to 2.50" of liquid but with different temperatures (and low track) and hence show anywhere from 2-20" of snow there (yeah that is what we are dealing with).

Even for Den/Bou and the front-range, we are looking at a legit range of 0.25" to 1.50" depending on the model (although latest high-res models like HRRR and RRFS have been more consistent, showing closer to 0.50"-1.00"+ with highest amounts near the foothills and from Boulder north to Ft. Collins).

So take the forecast amounts with a grain of salt. Still looking at overall impacts from 6am Tue to 12pm Thu.

Still questions on if we get another little wave and colder air on the back-side of the low (as ECMWF is still showing) from late Wed into the day Thu, continuing into Thu evening potentially.

There is still a chance that Den/Bou will see a rain/snow mix or all snow falling by Thu am (and maybe some accumulation). Also looks chilly by Thu (highs in the 40s) and if it clears out Thu night, likely the first freeze of the season for Den/Bou (with lows in the upper 20s).

Some snow seems likely in the foothills by Wed into Thu (1-5" mostly above 8500ft), could be more in spots if things come together right (and we get that second wave).

For the north-central mountains also a tricky forecast (with a wide-range of wind-flow scenarios, and uncertain cold air timing), but overall looks like a good rain/snow event. Rain moves in Tue am but the heaviest rain/snow will be Wed afternoon into Thu am.

Initially the snow-level will be near 12k ft Tue morning, falling to 10k ft by late Tue night into Wed am and then falling to likely 8500ft by Thu am.

Looks like a widespread snow event for much of the mountains by Wed pm into Thu, even into the mountain valleys. So the local ski areas / higher terrain / mountain passes should get a good 5-10" of snow above 9kft by Thu am, favoring areas near the Cont. Divide. Refer to map for amounts.

Still looks like overall heaviest rain/snow amounts will be across parts of western CO near the western San Juans up to the Elks, Grand Mesa, Flat Tops and maybe even the Park Range (north of Steamboat, models show a bunch of precip there). 1-2.5" of liquid precip and 6-12"+ of snow above 9500ft.

As I mentioned some high uncertainty in the snowfall forecast for the San Juans, will depend on if the cold-air can make it in during the best southwest flow / lift

Thats all my thoughts for now. Getting stoked and nervous, fingers crossed it all holds!

First image is my preliminary rain and snowfall forecast map through Thu pm (it will probably change some tomorrow). Image 2 shows forecast total liquid precip from now through 6pm Thu from latest (18z) ECMWF model. Image 3 and 4 show forecast total liquid precip and snowfall from now through just 6pm Wed from very latest 00z HRRR model, it does not show the entire event, so could be more in spots. But take modeled rain/snow amounts with a big grain of salt, just shows where the best chances are.