Turnagain Pass

There were no new avalanches reported yesterday, which is likely partly due to the fact that there was very little traffic in the backcountry. The last known avalanche was a skier-triggered avalanche seen on Notch Mtn. in Girdwood on Friday.

With the weather quieting down today our main focus switches back to the weak layer of snow buried by last week’s storms, now 2 to 3′ deep. Prior to the storm, we observed a well-connected layer of surface hoar from the road up to ridgetops. This was sitting on top of a layer of faceted snow on shaded aspects, and on top of a sun crust on solar aspects. We saw avalanches failing on that interface four days in a row last week, and there is still a chance a person will be able to trigger a big avalanche on that layer today.

These persistent weak layers can be a real challenge to assess. With a depth of 2 feet or deeper, it is unlikely you will be able to gain a lot of info digging a quick hand pit and it is dangerous and unreliable to try to use test slopes to see how the layer reacts. That leaves us with full snow pits and stability tests to try to gain some information on how reactive the layer remains. We saw this layer producing reactive results in pits on Seattle Ridge on Saturday, and expect it to be very slow to change.

For now, we are still treating this layer with caution. With quiet weather on the way it is unlikely we will see natural avalanches, but we may still be able to trigger a large avalanche. The easiest way to manage the problem is to avoid steep terrain while the snowpack gains strength. If you are trying to get into steeper terrain, it will be important to take the time to carefully evaluate the layer of concern. This includes things like looking for fresh avalanche activity, paying attention to clear signs like shooting cracks or collapsing (which you might not always see, even when conditions are unstable), and digging quick test pits. Because of the higher uncertainty associated with persistent weak layers like the one we are dealing with now, it is a good idea to give yourself wider safety margins and avoid more consequential terrain.

Wet snow avalanches will remain likely at lower elevations that have seen rain on snow for the past two days. Snow surfaces are now saturated below treeline, making natural and human-triggered wet loose avalanches likely below treeline. There is a chance that a wet loose avalanche may pull out a larger slab as it travels downslope.

This is the challenging setup we are currently faced with. We got a very unstable test result in this pit on Saturday, and expect similar behavior today. 03.16.2024

Winds are expected to taper off quickly this morning, but after 24 hours of sustained easterly winds averaging 10 to 35 mph, it will remain possible to trigger an avalanche up to a foot deep on wind-loaded slopes. Be on the lookout for reactive wind slabs at upper elevations below ridgelines, steep rollovers, or loaded gullies. Be skeptical of stiff snow sitting on top of softer snow, and watch for clear signs of unstable snow like shooting cracks or fresh avalanches. Unlike the persistent problem mentioned in Problem 1 above, these wind slabs may be assessed quickly using travel tests like hand pits and test slopes.

Although the fresh wind slabs that have formed over the past 24 hours may not be huge on their own, they have the potential to step down to the weak interface mentioned above, making a much bigger avalanche. With challenging avalanche conditions like we have today, it is usually best to keep your terrain objectives simple so you don’t get caught by surprise.

Strong winds were building fresh wind slabs through last night. They are expected to calm down today, but those fresh wind slabs will remain reactive through the day. 03.18.2024