Turnagain Pass Avalanche Forecast

Thumbs up for snow and thumbs down for wind. Human triggered wind slabs, 2-3′ deep, will be likely in steep wind-loaded terrain, especially on unsupported slopes and in cross-loaded gullies. Yesterday’s storm brought about a foot of snow (1″of SWE) to the forecast area with periods of snow falling around an inch per hour. After the mostly dry month of February it really felt like a welcome return to winter. With the snowfall the winds were easterly 10-20 mph with gusts into the 30s. They were definitely strong enough to blow snow around and form wind slabs as observers noted. Last night the winds shifted to the northwest and are forecast to blow 15-30 mph with gusts into the 40s today. As we have mentioned 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 pattern also increases through channeled terrain and can be more pronounced in Crow Pass and Portage. Because of the flip flop in wind direction there may be wind slab on all aspects.  Remember, expect any wind slab you find to be sitting on weak faceted snow and/or surface hoar and that they may be triggered remotely. The wind slabs may also be on a somewhat of spectrum from really stiff and easy to identify in the Alpine to softer slabs that are just slightly more cohesive than the weak layer below at lower elevations.

What to look for if you’re headed out today:

• Areas with current wind-loading (Northwest winds should blow all day), natural avalanches and cornice falls are possible. Pay attention to what terrain is above you.
• Slabs lower on slopes from cross-loading, especially with the winds funneling through Turnagain pass from the south.
• Stiff snow over softer snow (punchy snow), does it feel slabby?
• Cracks shooting from your skis or machine
• Whumpfing (collapsing of the snowpack into those recently buried facets/surface hoar underneath the new snow)
• Avoid cornices. They may be tender and easy to trigger

Storm slabs: Yesterday below approximately 1400′, the snow that fell was upside down with heavier/wetter snow on top of drier colder snow and you may find some storm slabs in areas out of the wind. However, the cold temperatures overnight may have helped this situation.

Persistent slabs: There is also a chance that a wind slab avalanche triggered near the surface overloads the older weak layers in the snowpack and steps down creating a larger avalanche. This is another reason for extra caution today.

Sluffs: Steep slopes that are sheltered from the wind have a foot of new soft snow and a few inches of loose facets from before the storm. It will be easy to trigger dry loose avalanches (sluffs) in this terrain.

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Sunburst 24 hour Windrose. Note the direction change and the northeast winds 16-25 mph (yesterday’s winds).

The new snow slid easily on the faceted snow below yesterday in a shovel tilt test. Another 6″ of snow fell on top after this photo was taken. Tincan, 3.10.21.