Avalanche Forecast

Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.

Thursday night: Decreasing cloud, strong outflow winds from the northeast, alpine temperature -12 C

Friday: Mostly clear, strong outflow winds from the northeast, alpine high temperature near -10 C

Saturday: Clear, strong outflow winds from the northeast, alpine high temperature near -10

Sunday: Clear, moderate northeast winds decreasing to light, alpine high temperature near 0 C

With increasing and shifting outflow winds, fresh wind slabs are expected to form and become reactive to human triggering. 

In the aftermath of the storm earlier in the week, avalanches releasing on surface hoar layers have continued. Operators reported several large (size 2-3) avalanches breaking on both the March 9th and March 1st surface hoar layers from human and explosive triggers. Several of these avalanches were remotely-triggered. Check out this MIN from the Shames area for a helpful example.

The recent storm brought about a widespread natural avalanche cycle in the region over Monday and Tuesday. There were reports of numerous natural, explosives, and human triggered avalanches up to size 2.5.

The recent storm delivered 30-60 cm of new snow to the region with strong southwest winds. Winds have since shifted to the northwest and are forecast to shift again to the northeast and increase in a strong arctic outflow event on Friday. With this pattern, few aspects will be spared from wind slab concerns. 

The new snow is sitting on a weak layer of surface hoar buried 30-60 cm deep in many areas, especially in sheltered areas at treeline and below treeline. See this MIN from the Shames area that shows this layer when it was on the surface.The new snow will also be sitting on a crust on solar aspects (south through west facing slopes). 

There are several additional layers of surface hoar that are now buried 70-120 cm and 110-160 cm deep, and are likely the most prominent around treeline. On south through west facing slopes, this surface hoar may be sitting on a crust, which may increase the potential for triggering avalanches on these layers. Below about 1000m, the recent new snow is sitting on a melt-freeze crust.

A weak layer of facets that formed in January may be found about 150 to 200 cm deep, and an early season melt-freeze crust lingers at the base of the snowpack. These layers have produced a few very large natural and explosive triggered avalanches over the past two weeks.

• Recent wind has varied in direction so watch for wind slabs on all aspects.
• Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
• Continue to make conservative terrain choices while the storm snow settles and stabilizes.
• Be aware of the potential for large avalanches due to the presence of a persistent slab.