Turnagain Pass

There were no known avalanches reported yesterday. The last human-triggered avalanche occurred on Sunday in the Library, where two skiers were caught and carried, with one sustaining minor injuries. The avalanche likely failed on a persistent weak layer buried about a foot deep. More details in this observation.

Today should be a fairly quiet day of weather, with light westerly winds and partly to mostly cloudy skies. The main concern to watch out for today will be triggering an avalanche where yesterday’s winds built a new round of wind slabs. With sustained winds around 15-20 mph for most of the day yesterday, it will still be possible to find reactive wind slabs today, especially at upper elevations near ridgelines, in steep gullies, and below convex rolls. The storm ended up on the light end of predicted precipitation totals, with most of our advisory area only seeing 2-4″ snow, and this will make it so the recent wind slabs should be a foot deep or less.

It may be tricky to spot unstable pockets from a distance, but there are some easy ways to assess as you travel today. Take the time to hop off your snowmachine or step off the skin track to see how the snow surface feels, before getting into steep terrain. If you notice stiffer snow near the surface, or especially if you see shooting cracks, you have found an unstable setup. With modest snow totals and light winds these wind slabs should be fairly quick to heal, but it is a good idea to navigate terrain carefully today while they are still reactive.

Dry Loose Avalanches (Sluffs): It is likely people will be able to trigger sluffs in steeper terrain that hasn’t been hit by the winds. These are unlikely to be big enough to bury a person, but can still be dangerous if they were to carry you through higher-consequence terrain like cliffs, rocks, or trees.

In addition to the problems related to the new snow mentioned above, we are also still concerned with the potential for triggering a larger avalanche on one of the weak layers buried in the upper 2-3′ of the snowpack. This includes a layer of surface hoar that was buried on 2/15 and is now 1-2′ deep, and a layer of near-surface facets buried 2-3′ deep that was buried on 2/5 and sits on top of a crust at elevations below 2000′. These problems are becoming less likely, but the poor structure is still there and we are still seeing unstable test results failing on these layers in some of our snowpits. It is important to assess these weak layers before moving into steep terrain so you don’t get caught off guard. As they become more stubborn they are becoming less likely to give warning signs like shooting cracks or collapsing prior to avalanching. It is getting to the point where these layers are getting too deep to assess with test slopes, and the best way to get an idea of how they are behaving where you are traveling is to dig a quick test pit. If you want to avoid the problem entirely, you can avoid steeper slopes.

That test result circled in red indicates that it is still possible to trigger an avalanche on that weak layer. This was John’s pit on Eddie’s two days ago, and it is likely very similar today. 02.22.2023

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In areas with a thin snowpack (i.e. Silvertip and the southern end of the forecast region to Summit Lake) there are various weak layers near the base of the snowpack that remain a concern. For these areas, triggering a larger avalanche is not totally out of the question and a more cautious mindset is recommended.