Avalanche Forecast

Archived

Dec 2nd, 2017–Dec 3rd, 2017

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

Northwest Coastal.

The recent storm snow will need time to settle and may be reactive to rider triggers. Storm slab avalanches could step down and trigger deeper layers within the snowpack, initiating large avalanches.

Confidence

Low - Due to the number and quality of field observations

Weather Forecast

Sunday: Mix of sun and cloud. Ridgetop winds light from the North West. Alpine temperatures near -6 and freezing levels 500 m. Monday: Mostly cloudy with up to 10 mm precipitation. Alpine temperatures near 0 degrees and freezing levels rising from 800-1500 m. Ridgetop winds strong from the South West.Tuesday: Mostly cloudy with light precipitation. Alpine temperatures near 0 degrees and freezing levels 1500 m. Ridgetop winds light from the South West.Check out the Mountain Weather Forecast for details.

Avalanche Summary

Considering the amount of new storm snow there has been no recent avalanche activity reported. I remain suspect of the new snow and the bond to the buried crusts, especially the basal crust. I would be diligent and use a conservative approach to route selection while traveling through low consequence terrain. The new storm snow will need more time to settle and adjust to the layers beneath. Storm slabs may be reactive to rider triggers. Check out the Mountain Information Network for recently posted observations around the Shames area. Give info, get info.

Snowpack Summary

Recent accumulated storm snow amounts are from 100-130 cm and seem to be settling quickly with average snowpack depths 100-150 cm at treeline elevations. Deeper deposits of wind slab may be found on leeward slopes. This storm snow now sits above a 5-10 cm thick crust that was buried a week ago. Digging down 90-160 cm exists a crust/facet combo buried at the end of October. Recent snowpack test results are showing hard compression tests with sudden collapse results. I would keep this on my radar through the weekend to see how the snowpack adjusts to the new load.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.