Turnagain Pass

If you have been out the past couple days enjoying the wind board and melt-freeze crusts, you may be thinking, “Snow available for transport??? No way!” However, with an inch overnight and forecast winds strong enough to erode into old snow, don’t be surprised by fresh wind slabs forming later today. Triggering a wind slab also has the potential to step down to weak layers buried in the top 3′ of the snowpack and create a larger avalanche (more in Problem 2).

With the little bit of snowfall last night/early this morning the winds were easterly 10-20 mph with gusts into the 30s. The winds will shift to the northwest this morning and blow 20-30 mph with gusts into the 40s today. Expect winds to increase throughout the afternoon and into tomorrow. Winds may blow into the 70s in the mountains closer to Seward overnight. As we have mentioned before, this wind flow direction (from the NW) 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.  This wind pattern also increases through channeled terrain and can be more pronounced in Crow Pass and Portage. The mountains from Summit Lake south to Seward are forecast to see the most wind and the snowpack has more sensitive buried weak layers. Although these areas are out of the CNFAIC forecast zone we want to highlight the potential for natural avalanches to become likely as the winds build.

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.
• Avoid cornices. They may be tender and easy to trigger.

Loose snow avalanches: Steep north facing slopes that are sheltered from the wind could have loose snow sitting on top of firm surfaces. Triggering dry loose avalanches (sluffs) in that terrain is possible today and wind loading could trigger natural sluffs.

We are still talking about a few layers of facets and buried surface hoar in the top 3′ of the snowpack. Shaded aspects, the ones that are most inviting with dry snow, are the most suspect place to trigger these now, as southerly slopes have various sun crusts. We are always concerned about something adding more load and tipping the balance causing one of these deeper layers to fail. With the winds forecast today this is on our radar. Winds channeled from the south could overload northerly aspects. Triggering a shallow wind slab or a cornice fall could potentially step down to a buried weak layer and cause a larger avalanche.

Knowing these layers are there, listening/feeling for whumpfing and watching for any other signs of instability are good things to keep in mind. As always, use good travel protocol, and consider the consequences if an avalanche does occur. Don’t forget natural avalanches will become possible today as wind loading increases.