Turnagain Pass

There were several wet loose avalanches that were reported during yesterday afternoon’s warm weather. These were both natural and human triggered. All these were reported to be on the smaller side. Evidence of a handful of storm slabs from the stormy weather late last week were seen in the Portage/Whittier region. These were naturally occurring from the storm – more details HERE. There was also a recent glide avalanche seen in the Skookum drainage.

A bunch of skier triggered rollerballs, the precursor to wet loose avalanches, on a southerly slope in the Portage/Whittier region. Photo by Graham Predeger 4.13.2024.

Recent glide avalanche in the Skookum drainage. Seen from the Seward Highway. Aleph Johnston-Bloom, 4.13,2024.

Mostly sunny skies and springtime weather is expected again today and into tomorrow, Monday. With many folks seeking out cold dry powder on mid and upper elevation shaded slopes, be aware there is a lurking weak layer. This layer is a combination of small facets and buried surface hoar. It has also been found on solar aspects on top of a crust. On these solar aspects, triggering a slab is much more likely when the surface crusts are soft and melting.

A skier remotely triggered a slab in the Girdwood area on Friday that was around 2 feet deep (more details in John’s forecast from yesterday) and a group at Turnagain Pass had multiple unstable test results on an upper elevation northerly aspect yesterday. Hence, triggering what appears like a surprise slab avalanche is within the realm of possibilities. The video below is from that group and shows one of two Extended Column Tests they performed. They were in the upper Spokane Creek area on a north aspect at 3,400′. How reactive this layer is in the forecast zone is uncertain, which is common for these tricky weak layers. Having a crust underneath makes them tricker. Crusts can prolong the healing process and provide a slick bed surface if an avalanche was to be triggered.

We recommend carefully evaluating how well the snow from last week is bonding to the old snow/crust underneath before committing to steeper terrain. Persistent weak layers can cause avalanches on lower angle slopes and be triggered remotely (from the side, top, or bottom). To avoid the problem entirely you can always stick to lower angle terrain.

With a clear night, we can expect a solid re-freeze in the lower elevations and on most solar aspects. With cool ambient temperatures today it may take the sun until later this afternoon to soften the crusts. As is a normal springtime routine, keep a close eye out for when the crusts do soften. Once the top several inches are wet and saturated, then wet loose avalanches should become easy to trigger.

Cornices:  Strong sun can also cause cornices to start breaking off, and there are a lot of ridgelines still holding onto huge cornices. Try to avoid spending time underneath cornices if they are receiving direct sunlight and give them a wide berth if you are traveling along a corniced ridge.

Glide Avalanches:  As the spring rolls on, don’t forget to watch for dark opening cracks on slopes. These are glide cracks and can release into a very destructive avalanche at anytime. If needing to pass under them, we recommend go fast and one at a time. If possible, avoiding being under them is the safest choice.