Avalanche Forecast

Archived

Feb 3rd, 2023–Feb 4th, 2023

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

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 unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

Glacier.

Storm slabs building on top of the low density snow that fell early in the week will remain reactive through the weekend.

A lingering weakness deep in the snowpack mean that storm slabs could step down and produce larger than expected avalanches. Minimizing overhead exposure and ensuring you do not ski cut slopes above other parties, are both good ways of managing this risk.

Confidence

Moderate

Avalanche Summary

On Friday we received a report of a natural size 2.0 slab avalanche from the South face of Bruins peak.

On Thursday there were reports of a size 2 avalanche from Frequent Flyer and a size 1.5 from Cheops North #4.

Wednesday-Thursday there was a natural cycle in steep terrain in the highway corridor of loose snow and slab avalanches failing in the recent storm snow. Avalanches were mostly size 1.5-2, with isolated size 2.5-3.

A natural cornice failure triggered a size 3 deep persistent slab on the SE slope of Grizzly Peak on Saturday.

Snowpack Summary

Snowfall and strong winds will continue to build storm slabs overnight. The 40-60cm of recently accumulated snow sits on a firm surface of old wind-effect in the alpine/treeline and a melt freeze crust below treeline.

The early Jan surface hoar layers are buried 60-90cm and were most prevalent at treeline. The November 17th weakness can still be found near the base of the snowpack in many areas - this layer is mainly facets, with a crust and/or old surface hoar in some locations.

Weather Summary

The next "storm" arrives tonight into Saturday, bringing steady flurries and strong alpine winds.

Tonight: Snow (5-10cm). Alpine low -8*C. Moderate, gusting strong, SW ridgetop winds.

Saturday: Flurries (~5 cm), Alp High -5*C, Freezing level 1300 m. Moderate SW winds.

Sunday: Cloudy with scattered flurries. Low -9 °C, High -5 °C. Light SW wind.

Monday: Cloudy with scattered flurries. Low -12 °C, High -7 °C. Light West wind.

Terrain and Travel Advice

Minimize exposure during periods of heavy loading from new snow and wind.
Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.
Storm slabs in motion may step down to deeper layers resulting in large avalanches.

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.