Avalanche Forecast - Rollins Pass, CO
Archived - NOT CURRENT

Issued on:Fri, Jan 6, 2023 at 4:30 PM

Avalanche Forecast:

Danger Level for Jan 7
3 - Considerable - Above, Near and Below Treeline

You can trigger a large, deadly avalanche on northwest through east to south-facing steep slopes. You are most likely to trigger an avalanche from an area of shallower snow and it may break near the ground on weak layers buried one to three feet deep. You can trigger these avalanches from the bottom of a slope or from a distance and they can break wider or run farther than you anticipate. Be cautious of wind-drifted slopes that face any direction, but especially easterly-facing slopes below ridgelines, downhill of convex rollovers, and in gully features. Any steep slope with smooth, bulbous pillows of snow above weak snow at the ground is suspect; a small avalanche can easily trigger a larger more deadly slide. If you see signs of unstable snow like cracking or collapsing, move to slopes less than about 30 degrees that are not connected to larger, steeper slopes above.

Avalanche Problems

Aspect/Elevation
All Elevations on all aspects other than W and SW

Likelihood: Likely

Size
Small - 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.

Forecast Discussion
Issued on: Fri, Jan 6, 2023 at 4:30 PM

Northern Mountains Regional Discussion

As we move away from the New Year's Eve snow cycle, we grouped the Northern Mountains by areas with similar snow depths - deepest, deeper, and not-so-deep. The deepest areas, like the Park Range and Flat Tops, will see the danger from Persistent Slab avalanches diminish the quickest. Whereas that process may be slower in the deep and not-so-deep areas like the Gore Range, Front Range, and Summit County.

The most likely way to trigger a large Persistent Slab avalanche across the Northern Mountains is from a shallow area of the snowpack. As slab thickness increases, your weight can only affect the deeply-buried weak layers in shallower areas, making Persistent Slab avalanches more difficult to trigger. As the Persistent Slab problem becomes more stubborn to trigger and gives riders less feedback, it can be easy to get lulled into making a poor slope decision. It can be very difficult to recognize the thinnest parts of a slab from the surface, especially with the combination of new snow and wind. Easterly-facing slopes have been the most dangerous, but be cautious around any slope that has recently developed a slab. The snowpack will be thinner in these more recently covered areas making it easier to trigger an avalanche.

The deepest areas in the Northern Mountains are the Flat Tops and Park Range. The snowpack is about 55-65 inches deep in these areas. Deep enough that it is becoming harder to affect basal weak layers with the weight of a person or a single snow machine. While it is still possible to trigger a deep and dangerous avalanche that breaks near the ground in these areas, finding the right spot to do so is becoming more difficult. You are more likely to trigger a smaller avalanche in the recent storm snow; either on the most recent interface or on weaknesses that are lingering from the New Year's Eve storm cycle. There has been enough snow over the holidays that one of these avalanches can still bury and kill you. Don't let your guard down because a Storm Slab is not as scary as a Persistent Slab. Also, remember that if you trigger a small avalanche in the new snow it could easily step down and trigger a larger avalanche.

The northern Front Range, Rabbit Ears Range, Gore Range, and Medicine Bow Mountains are not far behind the more northern areas with about 40-50 inches of snow on the ground. The remainder of the Northern Mountains, areas like the Indian Peaks Wilderness, Berthoud Pass, and Loveland Pass, are the most shallow with snow heights of about 25-35 inches. It will take additional base-building storms in both of these areas before we can begin to travel without thinking about causing failures in basal weak layers; the deeper areas will cross that threshold first. Snow and wind on Friday and Saturday in both of these areas will create slabs of wind-drifted snow that can avalanche. Again, while these avalanches are not as dangerous as a large Persistent Slab, they can still harm or kill you. Like the storm instabilities further north, the hazard from these avalanches should diminish in the next few days. However, as the danger diminishes in both of these areas in the coming days, it is because the probability of triggering a Persistent Slab avalanche decreased, not because the snowpack structure improved.

As we move firmly into a low-probability, high-consequence scenario it is important to remain patient. Don't let diminishing feedback from the snow and less natural activity tempt you onto the wrong slopes. There will be plenty of time to ski steep terrain when avalanche conditions improve. For now, continue to practice recognizing slopes less than about 30 degrees without overhead hazard as safer areas to recreate. With a suspect and somewhat unpredictable snowpack beneath your feet (or machine) in most areas of the Northern Mountains, threading the needle around a dangerous Persistent Slab avalanche problem is rolling the dice - wait for your odds to improve.