Archived forecast for Sunday, December 10, 2023
This is archived here due to a significant avalanche incident in the area on Dec 9.

Date Issued: Saturday, December 9, 2023 at 04:00
Valid Until: Sunday, December 10, 2023 at 04:00
Prepared by: SH

Up to 60+ cm of recent storm snow will take time to settle over the weaker basal layers. A spike in wind starting Saturday afternoon will be a factor in keeping the danger elevated.

Saturday:

Alpine: 4 - High
Treeline: 3 - Considerable
Below Treeline: 2 - Moderate

Travel and Terrain Advice

Avoid exposure to overhead avalanche terrain, avalanches may run surprisingly far.

Avalanche Problems:

Avalanche Problem 1: Wind slab
What Elevation? - Alpine
Which Slopes? - North, Northeast, East, Southeast, south, Southwest, West, Northwest
Chances of Avalanches? - Likely - Very likely
Expected Size? - Small - Large

Winds will start to increase mid-day at higher elevations. With lots of snow to transport, wind slabs could form and fail quickly. Once initiated, they could trigger deeper slabs. Watch closely for their development and consider your exposure to overhead terrain in gullies.

Avalanche Problem 2: Deep persistent slab
What Elevation? - Below treeline, Treeline, Alpine
Which Slopes? - North, Northeast, East, Southeast, south, Southwest, West, Northwest
Chances of Avalanches? - Likely
Expected Size? - Small - Large

The lower snowpack comprises two layers. Facets and a crust lie at the base, and the Dec 2nd layer of surface hoar, facets and crust above. These layers may be separated a bit in the alpine but, in many places, are right above each other. Avalanches can be significant in size and run below treeline.

Avalanche Summary

Avalanche control Friday produced results to size 2.5. Most were observed initiating on the basal facets, but it is unknown what layers many slid on. As skies clear, there are more observations of natural avalanches from the last few days. Most are up to size 2.5, failing on or near the ground.

Snowpack Summary

Up to 60 cm of storm snow overlies the Dec 2 layer of surface hoar, facets and a crust. Below this layer are basal facets and a crust formed in late October. We suspect there is some separation between these weak layers in the alpine, but at treeline and below, they are essentially the same layer. Snow depths range from 80-100 cm at treeline and up to 140cm observed in alpine locations.

Weather Summary

Winds will increase mid-day Saturday in the alpine to strong, starting NW and switching to SW. Temperatures will cool to -14 to -16 with mainly sunny skies. A trace of snow on Sunday with continued strong winds.

Confidence: Moderate