Avalanche Forecast

Issued: Mar 21st, 2015 8:51AM

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

Avalanche Canada rbuhler, Avalanche Canada

Touchy storm slabs will make for tricky conditions on Sunday. Conservative decision making is critical. Stick to low angle slopes and avoid avalanche terrain.Check out our blog on the current conditions: http://goo.gl/i7J4MQ

Summary

Confidence

Fair - Due to the number of field observations

Weather Forecast

A weak ridge of high pressure should bring a mix of sun and cloud for Sunday. Freezing levels are forecast to reach around 1500m in the afternoon and alpine winds are expected to be light. Good overnight recovery is expected during the forecast period with freezing levels falling to around valley bottom each night. On Monday and Tuesday, mostly cloudy conditions are expected with light convective flurries. Afternoon freezing levels should reach around 1500m each day and alpine winds should remain light.

Avalanche Summary

Avalanches observations have been limited due to the storm conditions but a widespread natural avalanche cycle is expected to be occurring at higher elevations. On Friday, several natural size 2 avalanches were observed. On Wednesday, natural and skier triggered slab avalanches were reported up to size 2. On Sunday, natural activity is expected to taper off as temperatures become cooler. However, if the sun is out in the afternoon, natural avalanches are possible from sun-exposed slopes. Human-triggering of storm slabs is expected to be a major concern for the next few days, especially at higher elevations where the snow is still dry.

Snowpack Summary

At higher elevations, new storm snow (30-50cm) sits over a variety of surfaces including moist snow, crusts, wind affected surfaces, and/or old wind slabs. Anywhere from 50-80 cm now sits over the mid-February persistent weak interface. This interface has recently been very reactive and may continue to produce large avalanches. In exposed terrain, strong SW winds have redistributed new snow into wind slabs on leeward features. The snow surface has been reported to be wet to around 1700m and moist to ridgetop. The snow surface is now expected to undergo melt-freeze cycles as freezing levels fluctuate overnight. The late-January crust/surface hoar layer (over 1m deep) and the mid-January surface hoar (around 1.5m deep) have been dormant for several weeks.

Problems

Storm Slabs

An icon showing Storm Slabs
Storm slabs up to 50cm thick may overlie a weak layer and are expected to be reactive to human-triggering for several days. These slabs may be moist or wet at lower elevations.
The new snow will require several days to settle and stabilize.>Use conservative route selection, stick to low angled terrain with low consequence.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 4

Persistent Slabs

An icon showing Persistent Slabs
The persistent weak layer buried mid-February is down up to 1m below the surface and has produced numerous large avalanches recently. Storm slab avalanches may step down to this layer.
Be aware of the potential for wide propagations resulting in large avalanches.>Remote triggering is a concern, watch out for adjacent slopes.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

3 - 6

Valid until: Mar 22nd, 2015 2:00PM

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