Turnagain Pass Avalanche Forecast

Two human triggered avalanches were reported yesterday. One on the northern most edge of our forecast zone and one just outside and to the south.

Berry Pass area north of Girdwood:  Skier triggered large slab avalanche in lower elevation terrain, crown around 600′ and on an easterly aspect. Skier is ok. This was reported to be up to 3′ deep in places, ~300+’ wide and running ~400′. Weak layer was facets below a crust. This is suspected to be the old January 28 crust.

Tenderfoot Ridge in Summit Lake (just to the south of the forecast zone):  Third snowboarder on slope triggered a slab avalanche around 300′ wide, 12″ deep and running ~600′. Rider was able to ride off slab and was not caught. The two members below deployed their airbags and rode away from the path, narrowly avoiding the moving debris. The slope was wind loaded and although the weak layer is unknown, it is likely this was a wind slab that sat on a buried weak layer. A big thank you to the party for writing in. See their report HERE.

Tenderfoot avalanche. Snowboarder triggered slab. 3.18.21. Photo by Alex McLain taken from the highway.

With sunshine in the forecast and the breezy northwest winds slated to decrease by noon, it could be a nice afternoon in the mountains today. Although the snowpack around Turnagain Pass itself is trending toward a LOW avalanche danger and triggering an avalanche large enough to bury a person is becoming unlikely, there are still traps out there. These traps could produce a larger avalanche and are most likely to be found in the periphery of our forecast zone to the north and to the south in the Kenai mountains. This was seen yesterday with the two human triggered avalanches. Regardless of where we travel, we need to evaluate each slope and consider the consequences if we happen to find and trigger an avalanche.

Persistent Slabs:  We know there are weak layers of buried surface hoar and facets in the top 3 feet of the snowpack. The slab above these layers has become quite loose and faceted, which is keeping it from sliding on many slopes (you can’t have a slab avalanche without a slab). It also sports a sun crust on many south slopes. However, daytime warming and wind loading can change all this and form a slab. In the lower elevations (below 1,000′), which is proving to be the most concerning, a thick layer of soft snow may be just stiff enough to act like a slab as well. These lower elevations also harbor a crust that is associated with the weak layers and can create a more tricky situation. That said, be suspect of lower elevation steep slopes.

Wind Slabs:  The ridgetop northwest winds bumped up last night and early this morning averaging around 10mph with gusts to 26mph at Sunburst. This is just enough that there could be some shallow new wind slabs in the forecast zone. To the south of the forecast zone (Summit Lake to Seward) wind slabs should be more prevalent as the winds blew stronger in that region. Keep a close eye out for any active or recent wind loading, stiff snow over softer snow and cracking in the snow around you. Wind slabs may be sitting on buried weak layers and could be larger than expected, as was the case in the Tenderfoot avalanche mentioned above.

Sluffs:  Steep slopes with a foot or so of soft surface snow (little wind effect and no sun crust) have been sluffing easily due to firmer snow underneath. As always, watch your sluff as these can be dangerous if they drag you into terrain traps like cliffs, trees, rocks, or gullies.

Sun effect:  If the winds truly die down today there could be enough solar heating to warm the surface crusts on southerly slopes. If this happens, these slopes will be ripe for wet loose avalanches and the potential for a slab avalanche that slides on that buried sun crust that sits about a foot deep.