Turnagain Pass

The northwest outflow winds did a number in many locations yesterday. Blowing snow and plumes were hard to miss for anyone out and about. Alex McLain in Seward was able to capture a natural avalanche in motion off the Resurrection Peaks behind the Lost Lake trail just north of Seward; note, this is outside of our forecast zone. The extent of other natural wind slab avalanches in the region is still being determined.

There were two human triggered avalanches yesterday. One was a snowmachine triggered wind slab on a small steep slope in Placer Valley. The other was a skier triggered persistent slab avalanche around a foot deep that failed on buried surface hoar in Placer Valley as well.

Natural avalanche and powder cloud behind the Lost Lake trail north of Seward. 2.19.21. Alex McLain.

Avalanche with powder cloud makes its way down the slope. 2.19.21. Alex McLain

Small wind slab, easily triggered by riders ascending this small steep slope. 2.19.21.

After the onslaught of northwest winds yesterday, winds have turned around and are blowing around 20 mph from the east this morning. These east winds are expected to quiet down by midday and though they may move a bit of snow around, any new wind slab is likely to be small and shallow. Snow surfaces around the region are quite variable; wind scoured, wind loaded, and even reports of slopes out of the wind harboring soft settled powder. That said, not only are the surface conditions variable, but the avalanche conditions as well. The avalanche danger will hinge on yesterday’s wind slabs, any possibility of new small wind slabs today, and lurking weak layers in the top 2′ of the snowpack.

If you are headed out, keep an eye out for any fresh shallow wind slabs that today’s winds might form. The wind is from a different direction than yesterday so soft snow may still be available to move around. Additionally, watch for harder wind slabs that were formed yesterday. These are worth avoiding as they may be sitting on weak snow, keeping them from bonding quickly. They also might simply just be stubborn and not quite healed yet. These slabs could be stiff enough to allow you onto them before realeasing. Any wind slab has the potential to step down to weaker layers buried in the top 2′ of the snowpack. More on that below.

Watching for the standard red flags will be key. Stiff snow over softer snow, cracks that shoot out in the snow around you, and whumpfing (collapsing) of the snowpack.

Loose snow avalanches (sluffs): If you are lucky enough to suss out a steep sustained slope with only loose surface snow, watch your sluff. These cold temperatures will continue to loosen surface snow and even eat away at the wind slabs out there.

Northwest winds blowing snow off of Byron and Carpathian Peaks yesterday. 2.19.21.

Triggering a slab avalanche breaking in a persistent weak layer of snow 1-2′ deep in the snowpack remains a concern. Unfortunately, a couple layers of buried surface hoar and facets sit in the top couple feet of the snowpack. Steep slopes with and without obvious wind effect are suspect. Not only are many older wind slabs sitting on these layers of weak snow, but areas with softer settled snow are as well. Add to that lower elevation terrain – under 2,000′. Between 1-2′ below the surface a layer of facets sits on a buried crust. This faceted layer produced an avalanche under Notch Mtn in Girdwood two days ago.

This is all creating a persistent slab avalanche problem. As we’ve been mentioning, it’s tricky because these layers are not reactive everywhere. Knowing what slopes could slide what ones are not likely to is tough to determine. Paying attention to any signs of instability and using good travel protocol are ways to help hedge your bets.