Avalanche Forecast

Issued: Mar 25th, 2017 8:00AM

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

ian gale, Parks Canada

Glacier.

Careful decision making is still required with lingering persistent weak layers. These layers are not always obvious and are variable across the terrain.

Summary

Weather Forecast

The low pressure system that brought us 10cm is moving out of our region & being replaced by a high pressure ridge. No significant snowfall today with freezing levels rising to 1400m. Winds will be light from the SW with occasional gusts to 45km/h. The stormy weather returns next week with 20-30 cms of snow forecast for Tuesday-Thursday morning.

Snowpack Summary

12cm of snow overnight and 30km/hr South winds have built variable soft slabs in the alpine and exposed treeline areas. Below 2000m, 20cm sits on a supportive crust. Storm instabilities down 30-60cm are present but becoming less reactive. Persistent layers exists down 150cm (February crust) and near the base of the snowpack (November crust).

Avalanche Summary

2 size 2.5 avalanches were observed from the highway corridor on the north face of Mt MacDonald. These slides were triggered during a spike in wind speed late in the day on March 22nd. There have been reports of cornices failing and triggering large slabs in steep terrain in areas near Glacier National Park.

Confidence

Due to the number and quality of field observations

Problems

Wind Slabs

Moderate winds and 10-15 cm of new snow have formed isolated wind slabs on lee features above treeline. Wind slabs may be poorly bonded to last week's storm snow and may step down to deeper layers if triggered.

Watch for shooting cracks or stiffer feeling snow. Avoid areas that appear wind loaded.Use caution in lee areas. Recent wind loading has created wind slabs.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Persistent Slabs

The month of March has been characterized by heavy loading of new snow and rain. After an intense avalanche cycle, the snow pack is still stabilizing. Deep weak layers have been failing sporadically leading to large avalanches.

Pay attention to overhead hazards like cornices which could easily trigger the deep persistent slab.Choose regroup spots that are out of avalanche terrain.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

3 - 4

Valid until: Mar 26th, 2017 8:00AM