Turnagain Pass

The remnants of widespread avalanche activity were seen yesterday morning. Despite the low visibility, the bottom of many avalanche paths that can be seen from the Seward Highway from Bird to Seward had large debris piles. Additionally, many steep rolling hills along the highway had avalanched up to 3′ deep (storm snow avalanches). There were three reports of avalanche activity in specific areas from yesterday:

Johnson Pass:  Several slab avalanches (2.5-4′ thick) were remotely triggered by snowmachiners on/near the Johnson Pass winter trail on steep rolls and hills. This group made it to an elevation of 2,200′ before turning around due to numerous Red Flags. In one case, they tested a very low consequence steep roll connected to a larger roll (40-60′ tall and ~40 degrees steep) and the entire face in every direction released. The larger avalanche paths in the area had avalanched and large debris piles were seen. On their way out they noticed many other steep rolls that they had triggered on the way in from flatter terrain.

Sunburst:  A large, 3′ thick, storm slab that released naturally earlier Friday morning was seen near the Sunburst up-track in the trees (photo below). Report HERE.

Wolverine:  A large natural slab avalanche was seen on the lower SW shoulder of Wolverine ridge on the northern end of Turnagain Pass. Slab was around 3-4′ thick and around 300′ wide. Likely released early Friday morning.

Storm slab avalanche in the ‘trees’ on Sunburst, in the mid-elevation. 1.8.21. Photo: Anonymous. 

It is not the day to push into steep terrain, nor will it be through the weekend as the danger rises again. Not only are avalanches likely to be triggered, they could be triggered remotely as was seen along the Johnson Pass trail. The mountains just had 2.5 -3.5′ of snow over the past three days along with strong east winds. Another 3′ or more is expected starting later today through Monday. It’s clear from what is listed above in our ‘recent avalanches’ section that we just went through a natural avalanche cycle and the snow isn’t bonding quickly. It fell on a weak surface (that surface we were skiing, boarding or riding on over the New Year), which is composed of small near surface facets (sugary snow) with buried surface hoar. Both these layers once buried can cause us grief as it limits new snow from bonding right away. How long will it take for the snow to bond this time, well that’s yet to be determined. With more weather on the way, it’s a moot point really as today we are still well within the 48-hour rule of letting the mountains adjust before getting onto the slopes that are luring us.

Storm slabs, these are defined as slabs composed of the new snow that have little wind effect, are equal in depth to the new snow, which is in the 2.5-3′ range. Storm slabs are what is present mostly in the trees and the type of avalanche most likely to catch a person today. Even on small steep rollovers an avalanche could pose a significant threat if you’re caught upside down and pinned in a terrain trap. For tree skiing or riding, make sure to keep an eye on your partners, be suspect of steep rollovers, and watch for cracking in the snow around you.

Although only 2-5″ of new snow is expected today, it will be the sustained moderate to strong ridgetop winds adding to the thickness of the wind slabs. Wind slabs could now be as thick as 5-6′, maybe even thicker.

Cornices: This storm was your classic Chugach sticky snow kind of event with just the right amount of wind to build large cornices. With more wind ramping up today ahead of this next Chugach storm, they may continue to release naturally and possibly trigger an avalanche below. Although these are hard to reach safely now, once these storm are over, they could be quite dangerous and easy to break.

Snow pit at 1,400′ on Seattle Ridge to the looker’s right of Repeat Offender slide path. 1.8.21.

4-7′ below the snow surface is the Dec. 1 rain crust/facet combination that exists at elevations between 1,000′ and 2,500′. This layer continues to degrade and weaken; turning into a faceted layer in places. Although it is unlikely that a person could trigger an avalanche on it, we are watching to see if a storm slab avalanche is able to step down and make it fail. So far we have no information on this, but it is a question that will help us assess if the layer is an issue moving forward or not.