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Avalanche Forecast

Archived

Mar 11th, 2022–Mar 12th, 2022

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

Regions

Little Yoho.

Winds have picked up in the alpine and fresh slabs should be expected Saturday as a cold front clears the region.

Give terrain with overhead hazard a miss until winds have backed off and continue to be cautious with solar slopes.

--more snow to come;)

Weather Forecast

Winds picked up Friday afternoon to Mod-Str W to SW as the warm front to a low passed just north of the forecast area. Up to 5cm of snow is expected overnight as the trailing cold front is set to pass over the region early Sat AM. Winds are expected to diminish following the passage of this front. Treeline temps will increase to reach -5C Saturday

Snowpack Summary

A new sun crust has formed over 5-10 cm of snow that sits over a sun crust on steep solar aspects. Winds on Wednesday developed reactive slabs in high alpine terrain and further slab development is ongoing Friday. February 16 sun crust down 30-40 cm on west, south and east aspects. January 30 facet or sun crust interface is down 50-80 cm.

Avalanche Summary

Tuesday a skier triggered a large persistent slab (size 3.5) on the SE slope of Vermillion Peak. Also Tuesday, we received a report of a cornice triggered size 2.5 slab on Mt. Carnarvon (YNP) - this one also likely ran on the crust. Groups on the Wapta for the week have reported several windslabs out as well as one large cornice failure.

Confidence

Intensity of incoming weather systems is uncertain on Saturday

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.

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.