Avalanche Forecast

Issued: Mar 13th, 2017 4:25PM

The alpine rating is high, the treeline rating is considerable, and the below treeline rating is considerable. Known problems include Storm Slabs, Deep Persistent Slabs and Cornices.

Avalanche Canada shorton, Avalanche Canada

It's uncertain how the snowpack will respond to a warm, wet, windy storm. It's time to be extra conservative with your terrain choices.

Summary

Confidence

Moderate - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

TUESDAY: Wet flurries with 5-15 cm of snow, strong southwest winds, freezing level around 1900 m.WEDNESDAY: Periods of snow and rain with 10-20 cm of snow above 1900 m and strong southwest winds.THURSDAY: Morning flurries then clearing in the afternoon with freezing level dropping to 1000 m, strong southwest winds.

Avalanche Summary

Natural storm slabs in the size 1.5-2.5 range have been reported in steep alpine terrain on a daily basis with the ongoing snowfall. Explosive cornice control on Sunday triggered numerous storm slabs and two deeper slabs that potentially failed on the February interface about 1 metre deep. Ski cutting produced several size 1.5-2 avalanches on wind loaded terrain features. Last Wednesday, a size 3.5 avalanche on Mt. Hosmer was a sign the deep persistent slab problem still exists as well.Expect a wide range of avalanche problems during the next few days of warm weather. Expect fresh storm and wind slabs at higher elevations, touchy cornices at ridgetops, unstable wet snow at lower elevations, and the possibility of large persistent slab avalanches on the February interface and basal facets.

Snowpack Summary

A warm wet storm will form fresh slabs at higher elevations while rain with fall below treeline. Strong winds will load lee features and continue to grow large cornices on alpine ridges. March has delivered regular storms with roughly 80-120 cm of snow sitting above crust and facet interfaces from February. Little is known about the distribution and reactivity of these interfaces. Isolated basal facets still exist in shallow snowpack areas and can produce destructive full-depth avalanches. Possible triggers for these deeper weak layers include cornice falls, rapid warming, or strong solar radiation.

Problems

Storm Slabs

An icon showing Storm Slabs
New snow and strong winds will form touchy slabs throughout the day, especially in the lee of exposed terrain.
Minimize exposure to avalanche terrain during periods of heavy loading from new snow, wind, or rain.Good day to make conservative terrain choices.Stick to non-avalanche terrain or small features with limited consequence.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 2

Deep Persistent Slabs

An icon showing Deep Persistent Slabs
Storm loading and warming may increase the likelihood of triggering large deep persistent slab avalanches. Concerns include basal facets in alpine terrain and a variety of crust and facet interfaces about a metre deep.
Pay attention to overhead hazards like cornices which could easily trigger deep slabs.If triggered the storm slabs may step down to deeper layers resulting in large avalanches.Be aware of the potential for large, deep avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 4

Cornices

An icon showing Cornices
Cornices are huge and are ripe for triggering with the warm weather.
Even small cornice falls may trigger larger avalanches.Minimize exposure to overhead hazard from cornices.Extra caution needed around cornices with current conditions.

Aspects: North, North East, East, South East, South.

Elevations: Alpine.

Likelihood

Likely

Expected Size

1 - 2

Valid until: Mar 14th, 2017 2:00PM

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