Colorado Avalanche Bulletin December 6, 2025
Not current - archived for an incident north of Loveland Pass

Issued on:Sat, Dec 6, 2025 at 6:15 AM

Saturday, Dec 06

Above Treeline: 4 - High
Near Treeline: 3 - Considerable
Below Treeline: 2 - Moderate

A potent storm with strong westerly winds and heavy snow will result in very dangerous avalanche conditions on north through east-facing above treeline slopes. The strong winds will build thick slabs over collapsible weak layers near the ground. Avoid traveling on or under these slopes. Be careful around, and consider avoiding, any north through east-facing slope where there is drifted snow or storm totals exceed 12 inches.

Avalanche Problems (2)

Problem 1: Persistent Slab

N-E Near and Above Treeline
Very Likely
Small to Large

Persistent Slab avalanches can be triggered days to weeks after the last storm. They often propagate across and beyond terrain features that would otherwise confine Wind and Storm Slab avalanches. In some cases they can be triggered remotely, from low-angle terrain or adjacent slopes. Give yourself a wide safety buffer to address the uncertainty.

Problem 2: Wind Slab

E-S All Elevations
Likely
Small to Large

Wind Slab avalanches release naturally during wind events and can be triggered for up to a week after a wind event. They form in lee and cross-loaded terrain features. Avoid them by sticking to wind sheltered or wind scoured areas.

Northern Mountains Regional Discussion
Issued on:Fri, Dec 5, 2025 at 4:30 PM

A large storm is moving into the Northern Mountains with strong westerly winds and heavy snowfall. The Park Range could receive 3 to 4 feet of snow, and the Gore Range won’t be far behind. We have issued an Avalanche Warning for these ranges. The main concern is upper-elevation slopes that face north through east, where weak, faceted layers exist near the ground. Observations from other areas with a similar basal weak layer have shown that avalanches are easily triggered, even with relatively light loading. We expect this intense loading event to result in a widespread avalanche cycle and very easily human-triggered avalanches anywhere that had at least a foot of snow on the ground before the storm.

The next most dangerous area on Saturday in the Northern Mountains is the Front Range down through Summit County. There is more forecaster uncertainty in these areas. We debated whether above-treeline locations could reach HIGH (4 of 5) danger with such a shallow snowpack, even with a large storm. With 18 inches of snow and strong winds, will slopes be connected enough to produce a widespread cycle of D2-sized avalanches? We erred on the conservative side. There is more certainty at lower elevations—where there is a foot or less of snow on the ground—that avalanches will generally remain smaller. Below treeline, most places will likely remain in Low (1 of 5) danger, but again we leaned higher due to the strong winds and the potential for wind-drifted slopes near the upper end of this elevation band.

It’s a tricky forecast: a large, intense storm arriving on top of very little early-December snow. When uncertainty is higher than usual, it’s wise to exercise patience, give the snowpack time to adjust, and evaluate how it responds to this load before moving into any steep terrain.