Turnagain Pass

The last human triggered avalanche that we know of was a large avalanche in the Squirrel Flats area above the Placer Valley back on Wednesday Feb. 14. There have been many natural wet loose avalanches since the temperatures started to climb in the middle of last week.

Large natural wet avalanche debris in the upper Girdwood Valley. This occurred late last week. Photo: Billy Finley, 02.17.2024

The easterly winds that have been howling through our forecast zone since early last week are easing slightly, but will likely still be strong enough to be moving snow around at the upper elevations today. After nearly a week of strong winds, the amount of soft snow on the ground available to be blown into fresh wind slabs is becoming limited, and that will most likely keep any fresh wind slabs on the smaller side. However, with sustained speeds of 15 to 30 mph avalanches may still be large enough to bury a person.

Look out for dangerous conditions on steep slopes below ridgelines, convex rolls, and in gullies. Pay attention to warning signs like cracks shooting out from your snowmachine or ski tips as clear indicators of unstable snow, but keep in mind you won’t always see these signs when conditions are dangerous. You may be able to assess this problem with travel tests like slope cuts or hand pits, but you can also manage the problem by avoiding the common problematic terrain features mentioned above. Remember, we are still dealing with a dangerous persistent weak layer that is buried deeper in the snowpack and this week-long wind event is still adding stress to that weak layer. More on this in Problem 2 below.

Wet Loose Avalanches will remain likely, especially in areas that are seeing rain on snow. These have been small for the most part, but they can be dangerous if they carry you into terrain traps like trees, cliffs, or gullies where debris can pile up deeper.

The winds were still able to find snow to blow around yesterday down in Summit, and it will be looking similar throughout the advisory area today. Photo: Trevor Clayton, 02.17.2024.

The deeper weak layer of faceted snow that formed back in January is trickier than the wind slabs mentioned above. We’ve found this layer to be most problematic at the mid elevations between around 1000′ to 2500′. This is concerning during a long wind event like we’ve been seeing since the most dangerous slopes are probably in the same elevation band where we are going to find the best surface conditions. From what we have seen lately, it seems like the weak layer is less concerning in Turnagain Pass than it is in Girdwood, Placer, or Summit. However, it still exists in Turnagain, and we think a person can still trigger a big avalanche on that weak layer.

The problem layer is around 1-2 feet deep on average, but it may be deeper where the winds have loaded the surface. As opposed to the wind slabs mentioned above, quick travel tests do not give good feedback on these layers. This one is going to be too deep to reliably assess with a hand pit, and there have been numerous accident reports in the past where people comment that they didn’t see any red flags before triggering a large avalanche. If you are thinking about stepping out into steep terrain, the only way to reliably assess this weak layer is to dig a snowpit near the piece of terrain you are considering. Stability tests can give you some information, but you can also just look for the thick layer of weak, sugary snow as a warning sign. The problem can be tricky to identify, and you can play it safe by sticking to low angle terrain a little longer while this layer continues to heal.

The AAS motorized Rec 2 group was out on the front side of Seattle Ridge digging in the snow yesterday. They were able to identify the January facet layer but did not get concerning test results. Photo: Graham Predeger, 02.17.2024