Avalanche Forecast

Issued: Mar 28th, 2014 8:00AM

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

danyelle magnan, Parks Canada

Glacier.

A mixed forecast, with some new snow but possibly some sunny breaks, will make this weekend interesting. Even a bit of sun can pack a punch and rapidly increase danger.

Summary

Weather Forecast

A series of weather systems are expected to pass through the region over the weekend. Today should be mostly cloudy with flurries. Freezing levels may rise to 1500m, with alpine temps of -1. Light, but gusty SW winds are expected at ridgetop. Up to 10cm are expected by Sat morning. This pattern will continue through the weekend.

Snowpack Summary

On shaded and northerly aspects dry snow exists above 1500m. Soft wind loaded pockets may be forming with moderate SW winds. On solar aspects breakable sun crusts exist, and overlie a series of crusts in the top meter which react with hard planar results in tests. The Feb10 layer is down ~2m, shallower in thin areas, and continues to be a concern.

Avalanche Summary

Yesterday, skiers reported easily triggering small size 1-1.5 slabs, where the storm snow failed on convexities and unsupported slopes. On Wed, loose moist avalanches triggered by skiers when a bit of sunshine provided a lot of warmth. These avalanches ran fast and and far, into mature timber, with some growing to size 2.5.

Confidence

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

Problems

Storm Slabs

20cm of new snow from earlier this week has bonded poorly to the snow below. It is especially reactive on solar aspects, where it is rapidly destabilized by even a little bit of sun. On lee aspects, soft slabs may exist from windloading by SW winds.

Start on small terrain and slope-cut the top of slopes before riding them.Be cautious as you transition into wind affected terrain.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

2 - 3

Persistent Slabs

Weak layers from early March, now buried a meter deep, are still reactive in tests. They are most likely to be triggered on solar aspects where sun crusts exist. Smaller avalanches may step down to these layers, resulting in a big avalanche.

Choose well supported terrain without convexities.Avoid shallow snowpack areas where triggering is more likely.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 3

Deep Persistent Slabs

A persistent weak layer from late Jan/early Feb remains a serious concern as it continues to be responsible for very large avalanches. This layer is variable in its distribution, is now buried up to 2m deep, is hard to trigger, and harder to predict.

Resist venturing out into complex terrain, even if you observe no obvious signs of unstable snow.Avoid convexities or areas with a thin or variable snowpack.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely

Expected Size

3 - 5

Valid until: Mar 29th, 2014 8:00AM