Wind slabs are once again our main concern, as winds ramp up during the day ahead of the next round of snow starting this evening. Winds are light out of the east as of 6:00 this morning, but are expected to to bump up to 20-30 mph with gusts of 30-50 mph by this afternoon. Although little or no snow accumulation is expected during the day, there is already plenty of soft snow on the ground that is ready to be drifted into sensitive wind slabs. The most likely place to find unstable snow will be on the usual suspects for wind slabs- steep slopes near ridgelines, convex rolls, and in gullies. Luckily this type of avalanche problem usually presents warning signs when conditions are unstable. Be on the lookout for shooting cracks, collapsing, and fresh avalanche activity as you travel today, and be cautious with your terrain choices as conditions are expected to become more reactive through the day. Yesterday I found reactive wind slabs on steep convexities in the Girdwood valley (details here), and similar activity is expected today. These avalanches will be most likely above 2000′, where most of the recent precipitation has been snow.
On some slopes there is a weak layer of snow sitting on top of the New Year’s crust, which was the culprit for a large human-triggered avalanche on Tincan Proper on Friday (more details here). This layer appears to be highly variable across the advisory area, but is somewhere around 2-3′ deep on the shallower end, and over 6′ deep in areas that saw the most snow over the past two weeks (Girdwood, Portage, Placer). The most likely place to run into trouble with this setup will be at higher elevations on slopes with a thinner slab sitting on top of the weak layer. It is possible an avalanche triggered near the surface could step down to this weak layer, resulting in a larger and more dangerous avalanche. Poor visibility and strong winds will make travel challenging in the alpine today, but if you are trying to get up high, this is the kind of setup that is worth looking out for. Be on the lookout for a stiff slab of snow sitting on top of weaker snow on top of the crust. This can be identified by digging a quick pit, probing with a pole as you travel, or hopping off your machine and looking for places where you can punch through relatively supportable snow in the upper 2-3′ of the snowpack. Ultimately, the best way to address higher uncertainty with a dangerous problem like this is to adjust your terrain choices, avoiding steep and consequential terrain until we have a better understanding of how this layer is behaving.
A strong system is approaching later this evening, bringing storm totals of 12-18″ by the end of the day tomorrow. It is looking like this storm is arriving late enough that it won’t increase the avalanche danger until late tonight, but be aware of increasing danger if the weather starts acting up earlier than expected. Tune in to tomorrow’s advisory for more details, and keep your fingers crossed for snow to sea level!
Cornices: Cornices continue to get larger and more sensitive as winds continue to blow snow off the ridgelines. These have a reputation for breaking farther back than expected, so be sure to keep a healthy distance from the edge as you travel along ridges. One group had a scary encounter with a cornice fall on Goldpan last Sunday (details here), and similar activity is possible today.
Loose Wet Avalanches: There is wet snow at the surface up to around 1800-2000′, which will make loose wet avalanches likely today. These are usually slow moving and on the smaller side, but they can have serious consequences if they carry you through dangerous terrain traps like trees, rocks, cliffs, or creeks. Be aware of this hazard as you travel around steep terrain in the mid and low elevations today.
Fresh wind slab release on a steep test slope at 2200′ on Notch Mtn., entraining loose wet snow as it slid. 01.22.2022
Rollerballs in the Tincan Trees yesterday, showing how wet the snow is at the surface. This snow is becoming wetter as above-freezing temperatures continue, making loose wet avalanches likely in steep terrain below 2000′. Photo: Adam Rothman, 01.22.2022.
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