Turnagain Pass

There were a few natural wind slab avalanches spotted along the Seward Highway near Girdwood yesterday. These were generally on the smaller side, and would have most likely occurred sometime between Wednesday night and Thursday morning. The last known human-triggered avalanche was on the south face of Magnum last Saturday.

The crown of a wind slab avalanche that failed near Kern Creek along the Seward Highway sometime Wednesday or early Thursday. 03.02.2023

Wind slabs will once again be our primary concern today as northwest winds ramp up through the day. These will be around a foot deep on average, but could be up to 2′ deep or deeper in areas that saw more snow on Tuesday and Wednesday (especially in the Placer Valley). The most likely places to trigger an avalanche will be just below ridgelines, in steep gullies and on convex rolls. The chances for encountering unstable snow increase as you gain elevation, where winds will be the strongest.

There are a few factors that increase the uncertainty with this round of wind loading. For one, the windiest areas might not have that much snow left to blow around after three days of strong winds. This will limit the potential size for a new round of wind slabs forming today. The other big question is whether these outflow winds will impact our core advisory area for the mountains near Girdwood and Turnagain Pass. These winds tend to favor periphery zones like Summit Lake and Seward, and often will leave Turnagain Pass relatively unscathed. Determining the extent of wind loading today will require some work once you are out. This can start on the drive up to the pass. Expect to find fresh and reactive wind slabs if you see snow blowing off the higher ridgelines as you head up. Once you are on the snow, be wary of any slopes where you find stiff snow on the surface, and be especially cautious if you notice cracks shooting through the snow from your skis or snowmachine. Areas that don’t get a lot of wind today will be closer to the moderate danger range, with fresh wind slabs more isolated and less likely to trigger.

Dry Loose Avalanches (Sluffs): For steep slopes that have been protected from recent winds, the light snow on the surface is likely to form fast-moving sluffs today. It is unlikely these will be big enough to bury a person, but they can still be dangerous in consequential terrain.

Turnagain Pass stayed out of the wind for the most part yesterday. Let’s hope that trend continues today… Photo: Megan Guinn. 03.02.2023

There are a few concerning weak layers in the upper 2-3′ of the snowpack that may be capable of producing bigger avalanches in isolated pockets. The most problematic terrain will be in areas with a thinner snowpack. This includes the southern end of Turnagain Pass (See this observation from Pete’s North on Wednesday) and down towards Summit Lake. Luckily, for most of our core advisory area it is looking like these layers are much more stubborn and less likely to trigger. It has been several weeks since we’ve seen any avalanches failing deeper in the snowpack, but it is worth keeping these layers in mind and adjusting your terrain use accordingly if you are traveling in a zone with a thinner snowpack.