Backcountry Avalanche Forecast
Sawtooth & Western Smoky Mtns
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Issued Friday, February 19, 2021 - 7:32AM
Expires Saturday, February 20, 2021 - 6:00AM
Author Ethan Davis

THE BOTTOM LINE

Continued snowfall and moderate winds have created dangerous conditions. Human-triggered avalanches and sensitive cornices are likely at upper elevations. You can reduce your risk by steering clear of steep slopes with drifts or stiff snow near the surface.

Avalanche Danger
Friday, February 19, 2021
Upper Elevation Considerable (3)
Middle Elevation Moderate (2)
Lower Elevation Moderate (2)
				
Avalanche Problem #1
Wind Slab
Upper Elevations, all aspects
Likely
Small (D1) to Large (D2)

Yesterday, Ben experienced cracking in freshly formed wind-drifts in the Fishhook drainage of the Sawtooths. Light to moderate wind and continued snowfall is expected over the next few days. Small, sensitive slabs and weak cornices will form in terrain exposed to the wind. These hazards are most likely in upper elevation terrain near and just below prominent ridgelines and in cirques beneath large cliff bands. 

You can greatly reduce your risk of triggering a slide by sticking to terrain that's more sheltered from the wind. Keep in mind that even small slides can have big consequences if they drag you through trees or bury you in gullies or creek beds. 

ADDITIONAL DISCUSSION:

In this zone, the December facet layer is buried beneath a very dense, 3-4'+ slab. It would take being in the wrong terrain, as well as a dose of bad luck, to trigger this layer. But if you did trigger a deep slab, you'd need all the luck in the world to survive it. You can reduce the odds of triggering a deep slab by sticking to sheltered, mid-elevation slopes where a more uniformly deep snowpack exists.

Forecast Discussion

In the past few weeks, snowpack characteristics have diverged significantly across our forecast area. In our northern zones, we are primarily dealing with "new snow" avalanche problems including fresh wind slabs created by new snow + wind (photo, photo, photo) as well as small slabs failing on mid-storm interfaces and loose snow avalanches in very steep terrain. Less snow has fallen in our southern zones and an overall shallower snowpack has kept persistent weak layers or "old snow" avalanche problems at the top of our problem list. 

In many ways, the snowpack around Banner Summit and in the Sawtooths simplifying. The rise and fall of avalanche danger here is primarily tied to storm activity. In the last week, a series of storms have deposited anywhere from 2.5-3.5' of snow (2.2-2.75" SWE). The ebb and flow of NW wind built wind slabs in exposed terrain. The Banner Summit area, with overall lower elevations and less steep alpine terrain, tends to keep its head out of the wind a little better than the Sawtooths. For this reason, the avalanche danger has remained elevated in the Sawtooths where both wind slab and loose snow avalanche problems are more prominent. 

Weak layers in these zones do exist. In fact, it's likely that the snowmobile-triggered slides near Cape Horn Summit on Tuesday involved a layer of weak facets and surface hoar that we've been tracking since late January. These avalanches (if indeed attributed to this weak layer) stand in glaring opposition of a trend of improving stability in the past week. So, as tempted as we may be to toss them aside as outliers, that's not how it works—more information is warranted. The primary weak layer of concern in our southern zones, and the one which produced extensive natural and human-triggered avalanche activity earlier this season is buried under a hard 4'+ slab of snow. Triggering an avalanche on a weak layer this deep is unlikely.