Turnagain Pass

There was skier triggered avalanche in steep, complex terrain on an unsupported and cross-loaded slope below Hippy Bowl. Fracture broke at skier’s feet then propagated uphill 25 feet. Avalanche initiation was slow, and skier had continued out of its path by the time it gained momentum. The avalanche was 9″ deep and 20′ wide.

Observers in Lynx Creek noted wind slabs both natural and small snowmachine triggered.

Small natural wind slab avalanches were also observed in Girdwood Valley.

Natural wind slabs on Captain’s Chair, 2.28.21. Photo: AAS Moto Level 1

Dear March Weather,

Please send lots of snow our way. The few inches in the forecast today won’t cut it and enough with the February wind events… We could use a good old crush n’ flush storm to get rid of the persistent weak layers and some powder would be lovely! Remember January? Just do that again. Thanks, Everyone

Yesterday observers from Girdwood to Seward noted blowing snow and wind affected surfaces as another northwest wind event impacted the region. Winds were sustained from the west/northwest throughout the day.  There were a few natural wind slab avalanches observed as well as the small skier and snowmachine triggered wind slabs noted above.  Triggering a wind slab will still be possible today but they might be a bit more stubborn. With snow forecast to fall throughout the day (2-6″/0.25 SWE), it may be hard to determine where the wind slabs are as the wind effect gets covered up. Consider wind slab habitat when choosing terrain. Slabs may be found near ridges, on steep unsupported slopes and in cross-loaded gullies. Watch for cracks shooting out from your snowmachine or skis, and ‘punchy’ feeling stiff snow over weaker snow under the new snow. Because of the multiple wind events and changing directions lingering wind slabs may be found on all aspects. If you do find and trigger a wind slab, remember it could step down to old buried weak layers deeper in the snowpack. In this case, a larger avalanche is possible (more on this in Problem 2).

Cornices: When traveling along ridgelines be sure to give cornices plenty of space, and minimize the amount of time spent traveling below them. Cornices could fail under the weight of a person on skis or a snowmachine, and might trigger an avalanche if the slope below is wind-loaded.

Wind transport on Gilpatrick in Summit Lake, 2.28.21 at 3 pm.

Cracking in recently wind-loaded snow on Eddies, 2.28.21. Photo Andy Moderow.

Click HERE for video.

As we have said now for weeks, this snowpack has to be viewed with some uncertainty and caution. We continue to track two weak layers of snow (surface hoar and facets) buried in the top three feet of the snowpack. The data continues to show triggering an avalanche in one of these layers remains possible. The small human triggered avalanches observed in lower elevations north of the Girdwood Valley (1100-1900′) on Friday and Saturday failed on one of these layers.  Observers also reported whumpfing associated with the buried weak layers in lower elevation terrain near Shark’s fin on Friday.

We know these layers are present in most areas and at all the elevation bands. The trick is, they are not reactive everywhere. They seems to be more of an issue below 2000′. However, a persistent slab avalanche in upper elevation terrain cannot be ruled out. Each snow event and wind-loading event add a little more stress to the snowpack. Triggering a recently formed wind slab or cornice fall may step down to one of these buried weak layers. There may be older hard wind slabs sitting on top of the weak layers allowing you to get well out onto the slope before an avalanche initiates or an avalanche may occur after other machines or skiers have have already ridden the slope.  In addition to trying to figure out where wind slabs lurk today keep in mind that these buried weak layers exist. Watch for signs of instability, follow safe travel protocol and evaluate terrain consequences.