Turnagain Pass

Seattle Ridge: Multiple loose and slab avalanches were visible from this week’s storm snow on Seattle Ridge.

Summit Lakes: Several natural avalanches were noted near Roaring Ridge, along with a glide avalanche on Gilpatrick.

Alyeska: Avalanche hazard reduction produced avalanches at Alyeska.

Don’t let the pleasant weather fool you– the snowpack is about to experience a rapid transition from dry to wet, and avalanche conditions will become very dangerous. There is a chance we could see just about every type of avalanche in the next few days, and the activity is expected to start this afternoon. The mountains near Girdwood have gotten 2-4′ snow this week, while Turnagain Pass has seen 1-3′. This storm snow is mostly dry above 1700′, and will become increasingly unstable as temperatures rise and the sun comes out to cook the snow. It will be tempting to get up into higher elevations to seek out drier snow, but the conditions may actually be the most dangerous where storm totals were higher and the new snow has not yet seen any melt or refreeze prior to the rapid warming expected today. Keep an eye out for classic signs of instability like shooting cracks and collapsing (‘whumpfing’) throughout the day, clear indicators that the snowpack is capable of producing an avalanche. Although the exact timing of these avalanches will be difficult to  predict, we can expect the likelihood of large natural and human-triggered avalanches to increase this afternoon.

We are entering uncharted territory for this season, and we have seen similar conditions result in large avalanches in the past. Avoid travelling on or below steep southerly slopes, especially later in the day, and use caution while approaching northerly aspects. Elevated danger is expected to continue through the weekend, as we are expecting more sunshine and continued warm temperatures.

Cornices: Warming temperatures will start to weaken large cornices, increasing the likelihood of cornice fall. As always, give cornices plenty of space and limit time spent travelling below them. A falling cornice could trigger a large avalanche today.

Loose Snow Avalanches: These will become more likely when the sun makes an appearance. They may be triggered naturally as snow falls off rocks and trees that heat up in the sun, or they could be triggered by a person in steep terrain. A relatively small loose snow avalanche will be likely to trigger a larger slab avalanche today.

Roof Avalanches: For buildings that have not already shed their snow, warming temperatures and melting snow will increase the likelihood of roof avalanches today. Pay attention to children and pets, and be mindful of where you park your car.

Recent avalanche activity on Seattle Ridge, likely within past 3 days. 04.15.2021

At elevations below 1700′, most of this week’s storm snow is already moist or wet. Mostly clear skies and cool temperatures overnight have allowed the snow surface to refreeze, which will improve stability for the first half of the day. But be aware of quickly deteriorating stability as temperatures rise and the snowpack softens this afternoon. It will become likely a person can trigger an avalanche in these lower elevations, and it may involve weak layers deeper in the snowpack (see problem 3).

Glide Avalanches: Two new glide releases were noted yesterday, and we will likely see similar activity today. Avoid travelling below glide cracks since they can release suddenly and without warning.

Glide avalanche in the Skookum Valley. 04.15.2021

The persistent weak layers buried in the upper surface have now experienced a significant loading event, and may start to see meltwater this afternoon. Both of these factors are increasing the likelihood of natural and human-triggered avalanches failing on multiple layers of buried surface hoar and near-surface facets. If we do see avalanches failing on these weak layers, they will be large and destructive. This problem will be important to keep in mind on all aspects, since it is not necessarily related only to warming, but also to the recent loading event.

It looks like spring is making a dramatic appearance to our advisory area. This rapid change means we can expect to see large avalanches, although the exact timing may be difficult to nail down. The best way to navigate the current avalanche conditions is by being extra conservative with your terrain choices, especially by entirely avoiding avalanche terrain on southerly slopes.