Turnagain Pass

After a little new snow and a couple days of temperatures climbing above freezing, we are seeing a cooling trend this morning. The snow that became moist or wet yesterday should have a delightful crust today…  Cooler temperatures, cloudy skies and WNW winds should keep the crust locked up and prevent any wet loose avalanches or warming issues in the snowpack. Our main avalanche concern continues to be persistent slabs due to layers of weak snow buried in the top 1-3′ of the snowpack. The natural avalanches in Summit Lake on Monday likely failed on these buried weak layers, as well as the most recent human triggered avalanches last week. These layers are still easy to find in snow pits and observers report variable results with snowpack tests. Some test results are pointing towards the potential for avalanches to be initiated on these layers. We have not been seeing widespread avalanches but we know these weak layers exist in the snowpack across the forecast area and south from Summit Lake to Seward. With wind loading today, triggering a wind slab avalanche (see Problem 2) could add stress to the layers below and result in a larger avalanche. Previously wind loaded slopes also harbor deeper slabs over the weak layers. Be on the lookout for areas that were previously wind loaded and those with any new wind loading. As always, use good travel protocol, and think about terrain consequences. This type of avalanche issue might allow you to get well out on the slope before the avalanche releases and it might not be the first person that triggers the avalanche.

Despite the weather forecast, because it is springtime and due the reality that we have dynamic weather, pay attention to cloud cover, temperature, and surface conditions. If the sun pokes out and/or temperatures shoot above freezing and you see signs of surface snow warming, move to shadier aspects/drier snow.

It was easy to see the line of buried surface hoar in a snow pit on Eddies yesterday, 3.30.21, at 2000′ on a N aspect. This weak layer was propagating in Extended Column Tests.

With moderate WNW winds in the forecast today and soft snow available for transport, watch for new small wind slabs to develop in the 6-8″ range. These are most likely to be found in the higher terrain along ridgelines. Watch for active wind loading and avoid any slope or cross-loaded gully with fresh wind deposited snow. Shooting cracks are a good indicator as well areas with stiffer snow over softer snow. As mentioned above, wind loading could overload buried weak layers and make it easier to trigger a larger avalanche. As we have said before, this wind flow direction is tricky for Turnagain Pass. It can funnel through the Pass from the south and load north aspects on the non-motorized side, while at the same time load the SE face of Seattle Ridge. It can also split around the Pass and not affect much of the terrain in the heart of Turnagain at all. This wind direction often has a greater impact near Crow Pass, through Portage, and south of the forecast area from Summit Lake to Seward.

Loose snow avalanches: Steep slopes are that sheltered from the wind have loose snow sitting on top of firm surfaces. It will be easy to trigger dry loose avalanches (sluffs) in that terrain today, and they can pick up enough volume and speed to carry a person. While it is unlikely they will be big enough to bury you, they can be dangerous if they drag you into terrain traps like cliffs, trees, rocks, or gullies.