Turnagain Pass

Girdwood Valley:  A large natural wet slab avalanche released yesterday evening on the lower east shoulder of Raggedtop. Note the wide propagation along the terrain. See more photos HERE.

Large wet slab avalanche that occurred yesterday evening on the lower east shoulder of Raggedtop. Photo taken by George Creighton from the Crow Creek Road 4.21.22.

After a brilliant 12-day stretch of clear weather, a good-sized low pressure is churning south of Seward and impacting the coastal mountains. This is bringing moderate to heavy rainfall up to 1,000′ coupled with strong ridgetop east winds. Around 3-5″ of snow has fallen overnight in the high elevations but another 5-10″ is expected today with another 5-10″ overnight tonight. The rain/snow line looks to stay near or just above 1,000′.

With springtime avalanches beginning to occur and a storm to add to the equation, we can expect a variety of avalanche problems in the mountains. The largest and most destructive will be wet snow avalanches that could occur in the mid and lower elevations. Rain, or wet snow, on the existing snowpack, along with cloud cover keeping the old surface from re-freezing, will both contribute to naturally occurring wet slab and wet loose avalanches. These could be very large and scour down to the ground, as seen in the wet slab that released on Raggedtop yesterday. These types of avalanches are common in the spring when the snowpack becomes saturated and wet. It looks as though we are headed into a period of the springtime shed cycle where the snowpack is literally falling apart and we should start to see more and more avalanches like this in the coming week. Something to be extra careful for when the skies clear again.

Another photo looking up the path of a portion of the wet slab avalanche from yesterday on Raggedtop. Photo George Creighton 4.21.22.

Glide Avalanches: In addition to the wet avalanche issues, glide avalanches are occurring as well. These can look similar at times when wet avalanches scour down to the ground giving the debris a dirty look. With the mountains starting to shed their snow right now, it’s good to be extra conservative and just avoid being under any glide cracks.

Glide crack on Cornbiscuit photographed by John on Wednesday 4.20.22.

In the higher elevations where dry snow is falling we can expect the typical wintertime storm snow avalanche problems to be forming. These are wind slabs on wind loaded slopes. They could be up to 2′ thick by this evening and very easy to trigger. Storm slabs are possible on slopes out of the wind in places where over a foot of snow piles up. And last, Cornice falls. I’d expect this storm to push some of the large cornices over the brink of failure.

This new snow is falling on a mixed bag of surfaces. On southerly facing slopes and all aspects below ~2,000′ a sun crust was present before the storm. On more shaded northerly slopes in the higher elevations there was a mix of soft snow and wind crusts with some surface hoar on top. The new snow may or may not stick to the crusts, but is most likely not going to stick that well to the loose snow and surface hoar. As with any rapid loading snowfall event, we should always be suspect of storm snow avalanches during and just after a storm. Looking ahead, once the sun comes back out all this new snow could become pretty touchy as the sun heats it up.

Sunburst 5am image of the snow storm up along the ridge. Images are found on the Sunburst weather station page HERE.