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Avalanche Forecast

Archived

Nov 19th, 2019–Nov 20th, 2019

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.

Regions

Glacier.

The Winter Permit System will go into effect Wed, Nov 20. Permits are required to enter restricted areas within Glacier National Park.

Reactive slabs are catching early season travelers by surprise. Choose conservative lines today.

Weather Forecast

A ridge of high pressure will begin a clearing trend around Rogers Pass for the remainder of the week. A mix of sun and cloud today, with light NE winds, and fzl at 1400m. Wednesday should be sun with clouds, light NW winds, and fzl around 1000m. Thursday will be similar to Wed with a weak inversion bringing warmer alpine temps.

Snowpack Summary

35-50cm of new storm snow overlies an early season snowpack, complete with a series of melt-freeze crusts throughout the height of snow. Mod/strong winds and mild temps have created a persistent slab in alpine and tree-line lee features. These slabs sit upon a crust/surface hoar/stellar layer and are easily triggered by human loading.

Avalanche Summary

Human-triggered avalanches to size 2 were reported from Balu Pass yesterday and the Asulkan Hut area 2 days ago. The Balu Pass avalanche buried the person to their neck and gear was lost. Numerous natural avalanches to size 2.5-3 were observed from Tupper, Macdonald, and Cheops during the storm Sunday morning.

Confidence

Due to the number of field observations

Problems

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.