Turnagain Pass

No new avalanches were reported yesterday. However, it’s likely that at least some wet loose slides occurred in steep rocky terrain during the afternoon hot temperatures. Two days ago there was a report of a natural slab avalanche seen in motion from Tincan, this was on Monday and pictured below.

Avalanche seen in motion on Monday while digging a snowpit on Tincan. Thanks to Bryce Barnes for snapping this pic and the added info! 3.18.24.

The springtime transition is beginning. Yesterday was the first ‘official’ day of spring and for the next 6 months our days will be longer than our friends in the lower-48. With increasing daylight and generally warming temperatures the snowpack will undergo a change from cold wintertime snow to warm/melt-freeze summertime snow. This transition can take weeks and create very large natural avalanches at times. Something to keep in mind for the next month or more.

Wet Loose Avalanches:  For today, despite the sunshine, a light westerly breeze may keep the snow a bit cooler than yesterday. However, surface crusts should melt to some degree by this afternoon. These crusts are found on southerly aspects and all aspects at the mid and lower elevations. A reminder that the warmest part of the day is between 2 and 5pm. Once these crusts melt then wet loose avalanches will become possible. Watch for indicator slopes like steep rocky terrain baking in the sun where the darker colors of rocks/vegetation enhances warming. This is often where wet loose slides start. Triggering a wet loose avalanche can be easy and inconsequential, but if caught very hard to escape from. These wet ‘sluffs’ can also trigger slab avalanches below.

Glide Avalanches:  Glide cracks are starting to open again. Pictured below is an opening crack on Eddies southerly face around 2,000′. If you see these cracks it’s best to avoid being under them, or go fast and one at a time, in case they happen to release into an avalanche.

Glide crack opening on Eddies south face. Seen from Tincan. Thank you to N. Dumont B. Matthys for the photo. 3.19.24.

There is a layer of weak snow and/or buried surface hoar between 2-3′ deep. It’s the layer under all that storm snow from last week. Snow pit tests are still showing concerning results, meaning the potential for us to trigger a large avalanche. Side note: for a reminder on the snow science jargon used in observations, check out Andrew’s Cheat Sheet on interpreting stability tests. The last avalanches we know of for certain were from last Thursday, but a few others, including the one seen on Monday on Seattle Ridge, may have released on this layer.

The most likely place to trigger a slab is where the surface still has soft settled powder (shaded steep slopes) or in the afternoon on southerly aspects when the surface crusts have melted. Essentially where the riding/skiing is best. The chances of triggering a slab 2-3′ deep is decreasing, but it’s still a possibility, which is that tricky situation we often find ourselves in.

It is difficult to assess buried weak layers because no obvious signs of instability may be present and the snowpack can ‘feel stable’. In this case, snow pits are the only tool that might provide useful information. Yet pit tests can provide false stable or inconsistent results and we don’t recommend relying entirely on pit information to make ‘go’ or ‘no-go’ decisions. If you decide to travel in steeper terrain we recommend giving yourself a wider margin for error, carefully evaluating the snowpack, and using safe travel practices to minimize your group’s exposure.

Snowpit at 2,700′ on a WSW aspect on Tincan from two days ago, Monday. Test results in an Extended Column Test showed a layer of buried surface hoar propagated across the column, a concerning test result. Photo and pit by Bryce Barnes 3.18.24.