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Avalanche Forecast

Archived

Dec 16th, 2013–Dec 17th, 2013

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

Regions

Little Yoho.

Expect another 15-25 cm of snow on Tuesday with very strong winds. Conditions have deteriorated over the past few days through this storm. Be patient, cold air arrives on Wed and with that the avalanche conditions will improve. GS

Weather Forecast

Another system embedded in a strong westerly flow will bring 15-25 cm of snow to areas around Lake Louise and Bow Summit on Tuesday, with less snow expected in southern areas. Winds will continue to be very strong (35-85 km/hr), with temps from -5 to -9. Clearing and cooler air arrive on Wednesday, with temps reaching -15 to -20 by Thursday.

Snowpack Summary

Areas on the west side of the Continental Divide have received up to 20 cm of snow in the last 36 hours, for a total of approximately 40 cm over the past four days. Strong to extreme winds at treeline and above have created windslabs in most open areas. Total snowpack depths range from 60-100 cm, with the lower half comprised of weak facets.

Avalanche Summary

Sunshine Village reported a ski cut size 2 avalanche that started as a 40 cm deep wind slab, then stepped down to the facets at the base of the snowpack (max fracture depth 150 cm). Similarly, Lake Louise avalanche control reported loose snow avalanches acting as a trigger for a deeper size 2 running on the weak facets near the ground.

Confidence

on Thursday

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.