Turnagain Pass

• Gulch Creek near Hope Y: Very large avalanche observed from a distance and assumed to be a wet slab releasing on the November facets above the Halloween crust. This crown was at least 1000′ wide and estimated at 6-8′ deep (see ob here).

Crown from a very large wet slab up Gulch Creek near the Hope Y observed from the road. Photo 4.20.22

• Crow Pass Area: Wet slab released on 4.19.22 while a group was skiing in the area. We suspect this avalanche occurred on the November facets above the Halloween crust.

Wet slab avalanche occurred after the glide avalanche had already released on a south aspect at around 3000′ near the Crow Pass trailhead.

• Twentymile: Very large glide avalanche up Twentymile drainage observed from the highway (see ob here).

Large glide avalanche up Twentymile drainage on a south aspect. Photo 4.20.22

The glorious spring weather we have experienced so far this week is on it’s way out today and increasing winds and scattered snow showers are expected to impact the area starting this afternoon. The increasing winds today have the potential to build fresh wind slabs at upper elevations, especially on north facing terrain where dry snow remains on the surface and will be more prone to wind transport. Wind slabs up to a foot deep are the primary avalanche problem today and will be possible for a person to trigger along ridgelines, cross loaded gullies, and convex roll overs, but they won’t be an issue until the winds start to pick up this afternoon. Until then the same normal caution avalanche conditions we have experienced so far this week are expected throughout the first half of the day.

Cornices: The warm temperatures and sunshine this week are weakening cornices and the potential for part of a cornice to randomly fall off or be more prone for human triggering from the ridgeline exists. Be aware if cornices are getting direct sun above you and try to avoid spending too much time underneath them if that is the case. Give them a wide berth if you are travelling along ridgelines today.

We have received two observations of wet slab avalanches over the past two days that appear to have released in the November facets above the Halloween crust, but we have not had a close enough look to know for sure (observations here and here). These avalanches are very large and destructive and we know that this weak layer and crust combination exists throughout the region and is especially prominent in areas with a thinner overall snowpack depth (e.g. Crow Pass, Summit Lake). Wet slabs are unpredictable but require melt water pooling in a weak layer in order to release, which means they are most likely to fail during times of high melt from the sun and warm temperatures. The weather moving in today might save us from having enough melt for more wet slabs to release, but it is still important to be aware of the potential for these very large avalanches.

The best way to avoid wet slab avalanches is to pay attention to how much the surface snow is melting during the day and move to another aspect if you start sinking in more than ankle deep or start to see wet loose avalanches releasing naturally.

Wet Loose Avalanches: Depending on the timing of the wind and cloud cover moving in today there could be enough time for melt freeze crusts to soften enough to cause wet loose avalanches in steep south facing terrain. Yesterday on the south face of Cornbiscuit my boots were sinking in about ankle deep at 2 pm and the potential for wet loose off the steeper south facing rocky terrain seemed to just be starting. If the clouds move in earlier in the day or the winds pick up and keep the snow surface cool we might not see much melt on the surface crusts.

Rollerballs and wet loose avalanches on the south face of Cornbiscuit. Photo 4.20.22