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Avalanche Forecast

Archived

Feb 17th, 2020–Feb 18th, 2020

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.

Regions

Little Yoho.

Good conditions this week as the snowpack and the weather stabilizes. The sun is higher in late February, so be aware of the increased power of solar radiation on the snowpack. Don't climb under large sun exposed start-zones when the sky is clear.

Weather Forecast

NW flow aloft will keep the temperatures relatively cool over the next few days, with overnight lows near -15 and daytime highs reaching -5. With the sun higher this time of year, be wary of the local heat that can develop in sheltered areas from solar radiation. No new snow and light winds are forecast for Tuesday.

Snowpack Summary

Continued settlement and cool temperatures are slowly stabilizing the recently formed windslabs, which could still be triggered in steep, loaded areas in the alpine. Suspect sun crust formation on steep S and SW facing terrain. Overall the deep snowpack is strong in Little Yoho with no significant shear test results.

Avalanche Summary

No new avalanches were observed or reported on Monday, but Sunday saw many windslabs up to size 2 and a couple of very large (size 3.5) avalanches that ran to valley bottom in adjacent forecast regions with shallower snowpacks.

Confidence

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.