High uncertainty in the forecast for the Sun-Tue storm sytem

10/28/26 8pm: Hi. Well, I'm not exactly thrilled with what I'm seeing in the model data for Den/Bou and the front-range in-regards to the Sun-Tue storm system. But the models continue to be all over the place, so there is time for it to change.

Still looks like a big event for parts of western / southwestern CO favoring the San Juans: 1-3" of liquid precip 1-2ft+ of snow.

Models still show wildly different solutions in terms of the trough evolution and where the dominant low will be.

ECMWF now shows a weaker low tracking much farther west / southwest (hence the focus over southwest CO) and much less for the northern front-range (and northern mountains for that matter).

GFS and GEM show a more split flow pattern with more energy in the northern branch eventually strengthening into a strong low that moves into east-central CO by Mon (its a completely different track than ECMWF, lol).

The issue for Den/Bou and the front-range is that the models show the dominant surface low setting up too far east (or northeast) and hence too much westerly downslope flow.

Although GFS shows strong wrap-around northerly flow on Mon night into Tue with a healthy batch of precip for parts of the front-range favoring the Palmer Divide (with even some good snow accumulation above 6500ft).

For Den/Bou snow chances look pretty low, although maybe a rain/snow mix late Mon into Tue am depending on how things setup. But still likely a decent shot of cold rain (and snow above 6500ft) from 2am Mon through 6am Tue (best chances 5pm Mon to 5am Tue). Maybe a rain/snow mix or all snow falling in the metro area by Tue am.

Even for the north-central mountains / I-70 corridor there is high uncertainty in how this will unfold. Latest ECMWF is very pessimistic with the low too far south. GFS, GEM and other models still show a good shot of snow for our local mountains. Most of it from Sun night through Mon night: 5-12" likely for the ski areas and mountain passes. Front Range mountains likely favored, but hard to say.

And as I mentioned with the broad southwest flow and deep moisture, pretty much a guarantee for Southwest CO: first some rain/snow from Fri night through Sat afternoon. Then the main event moves in by 5am Sun.

Could be some more flooding in spots near Durango to Pagosa Springs to lower Wolf Creek Pass (with 1-3" of rain in the forecast).

And heavy snow in the mountains down there, although does look like the snow-line stays north of 10k ft initially on Sun am, then falling to 9k ft by Mon.

Also looks like some good rain/snow for areas in western CO and near the Elks (Aspen to CB and in-between): 0.50"-1.50" of liquid and 8-14"+ of snow above 9k ft. And good rain for western CO as well.

Thats all for now.

I've include some multi-panel model plots show forecast total liquid precip and total snowfall from now through 5am Tue from NWS Blend of Models, GFS and ECMWF, you can see they have wildly different solutions for certain parts of the state. Second image shows forecast precip-type/rate at 12pm Mon from latest GFS (we need that surface low further southwest).