Avalanche Forecast

Wednesday night: Mostly cloudy, 3-8 cm of snow, strong northwest winds, alpine temperatures near -7 C with freezing levels dropping to valley bottom.

Thursday: Cloudy, 3-5 cm of snow, moderate southwest winds, alpine high temperatures around -8 C.

Friday: Mostly cloudy, 30-40 cm of snow falling overnight and through the day, strong southwest winds, alpine high temperatures near 2 C with freezing levels rapidly rising to 2000 m.

Saturday: Mostly cloudy, 5-10 cm of snow, moderate southwest winds, alpine high temperatures around -3 C, freezing level near 1200 m.

Several large (size 2) natural avalanches were reported in the region on Wednesday (check out this MIN from Zoa Peak). This avalanche activity occurred in the storm snow. 

Few observations are available from the northern part of the region where the deeper, persistent slab problem exists. In the widespread avalanche cycle a week ago, avalanches were observed running to valley-bottom and failing on deeply buried weak layers. See this MIN report of an avalanche involvement from last week for an example of this avalanche problem.

The possibility for large human-triggered persistent slab avalanches remains a concern in the northern part of the region (e.g., Duffey, Hurley, etc.), especially as more sensitive storm slabs create the potential for avalanches to step-down to these layers.

Storm snow totals came to 20-30 cm for most of the region, creating a widespread storm slab problem. At higher elevations, strong southwest winds are expected to exacerbate the reactivity of the new snow in drifted areas. The storm covered another recent layer of surface hoar and a sun crust on steep sun-exposed aspects.

The snowpack below varies significantly between the northern and southern parts of the region. In the north (e.g. Duffey, Hurley), the upper snowpack consists of around 50-90 cm of snow that overlies a weak layer from late November composed of sugary faceted grains and hard melt-freeze crust. This presents a persistent slab problem that may remain problematic for weeks to months with the potential to produce large and destructive avalanches. This persistent weak layer is largely absent in the south of the region.

• Continue to make conservative terrain choices while the storm snow settles and stabilizes.
• Avoid freshly wind loaded terrain features.
• Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
• If triggered, storm slabs in-motion may step down to deeper layers and result in very large avalanches.