Cooke City

Recent avalanche activity has been both impressive and dangerous, with 37 avalanches reported in the last 10 days. Very large, human-triggered slides breaking 2-5 feet deep are likely in steep terrain. Minimize or eliminate your exposure to slopes steeper than 30 degrees. Weak layers are less widespread on low-elevation slopes.

OVERVIEW

The primary avalanche concern remains persistent slab avalanches in which slabs of snow fail on weak layers buried near the ground. These weak layers developed when snow from October and early November turned into loose, sugary facets.

The differences between areas result from two factors:

1. Elevation: how much of the early-season snow melted back to dirt before snow began falling in late November.
2. The amount of snowfall over the last two weeks - The most around Cooke City (more dangerous) and the least around West Yellowstone and Island Park (less dangerous).

COOKE CITY

Recent avalanche activity around Cooke City has been both impressive and dangerous.

• Thirty-seven avalanches were reported in the last 10 days, many breaking 2–5 feet deep, with close calls, and a burial and rescue (avalanche activity log).
• Yesterday was the first day without a reported avalanche in over a week.

Last night, we received a great observation that discussed the incredible number of avalanches and seemingly stable test results. This highlights a time to ignore your stability test and focus on observed instability.

• Danger rating: CONSIDERABLE at middle- and upper-elevations. Largely avoid slopes steeper than 30 degrees.
• Danger rating: MODERATE at lower elevations. Weak layers are less widespread. Dig, test, and decide whether to dabble in some lower-consequence avalanche terrain.

BRIDGER RANGE, GALLATIN RANGE, MADISON RANGE, LIONHEAD AREA, ISLAND PARK

The likelihood of triggering a 1–3-foot-deep persistent slab avalanche has decreased in the mountains around Bozeman, Big Sky, West Yellowstone, and Island Park, but the underlying snowpack structure remains weak at middle and upper elevations. Warm temperatures have not eliminated the problem (Mt. Blackmore obs and video, Beehive obs and video).

Yesterday, I got my first look at snowpack on Saddle Peak in the Bridger Range. Because the terrain matches no components of the day’s travel advice, we choose to return to the ridgeline and back to Bridger Bowl Ski Area (video).

• Danger rating: MODERATE at middle and upper elevations. Evaluate for instability. Smaller, gentler avalanche terrain free of traps like gullies and trees is a good choice. Avoid steep, large, and high-consequence avalanche paths. For what it's worth, slopes where the skiing and riding are bad (meaning there is a thick melt-freeze crust) are generally safe for now.
• Danger rating: LOW at lower elevations. Avalanches are unlikely. This also applies to mid-elevation, south-facing slopes in the Bridger Range.

LOOKING FORWARD

We are all excited to return to snowy conditions. On slopes where the skiing and riding feel good and soft today, you are likely riding on “recycled powder,” also known as near-surface facets. This is a weak layer that forms during periods of high pressure, and incoming snow is likely to bond poorly to it.