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Avalanche Forecast

Archived

Jan 14th, 2023–Jan 15th, 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 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.

Regions

Glacier.

The warm temps and addition of new snow has initiated a steady cycle of size 3-3.5 avalanches out of steep, rocky terrain along the highway corridor.

The new storm slab may require several days to stabilize, stick to conservative, low consequence terrain. The possibility of avalanches stepping down to deeper weak layers persists, and would result in large destructive avalanches.

Confidence

Moderate

Avalanche Summary

There has been fairly continuous avalanche activity since Friday evening with numerous size 3-3.5 out of the steep terrain on Mt. MacDonald and Mt. Tupper, with some of these running over the snow sheds and full path into the creek.

Elsewhere in the Park there were several size 1.5-2.0 from Mt. Smart, Ross Peak, Mt. Abbott and Cougar Mountain.

On Wednesday, explosives training produced numerous size 1-2 avalanches in steep terrain, mostly failing on the Jan 3 surface hoar, which is now buried ~40cm. One result scrubbed to ground on a shallow rocky rib and then stepped down to the Nov 17 deep persistent layer on the slope below, with a 1 meter deep crown, resulting in a size 3.

Snowpack Summary

30cm of recent storm snow buries the Jan 12 surface hoar, and the Jan 3 surface hoar is ~20cm below that. The mid-pack consists of rounding facets and is gaining strength, while the bottom of the snowpack is weak and facetted with the Nov 17 facet/crust/surface hoar. This layer is ~50cm above the ground and has become less reactive in tests, but still shows 'sudden' results.

At tree line there is ~160cm, which is 70% of an average snowpack

Weather Summary

Sunday will be mainly cloudy with isolated flurries and sunny periods. Ridge-top winds will be light from the South with alpine temps ranging from -6 to -3. Freezing level will reach up to ~1700m.

Monday will have similar weather.

Tuesday will see increasing winds and cooler temps.

Terrain and Travel Advice

  • 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.
  • Use caution when approaching steep and rocky terrian.

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.