Avalanche Forecast

Issued: Mar 22nd, 2017 4:20PM

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

grant statham, Avalanche Canada

Little Yoho.

Although just over the peak of the avalanche cycle, we continue to see large avalanches running. The CONSIDERABLE danger rating below treeline exists due to the potential to be hit from above. Avalanches have been running to the valley bottom.

Summary

Weather Forecast

Southwest flow continues with flurries expected on Wednesday night, possible accumulations of 3-5 cm by Thursday. The temperatures will fall slightly on Thursday, but expect freezing levels to reach about 1500 meters with treeline temperature from -5 to -8. Winds will remain moderate from the southwest.

Snowpack Summary

100cm of dense, rounded snow comprises the upper half of the snowpack and sits on a variety of different foundations depending on location. In shallow areas (eg: Field ice climbs) the base is weak depth hoar. In deeper areas (eg: Little Yoho Valley), the base is rounded and stronger. Shears persist in the deep facets, and within the storm snow.

Avalanche Summary

Report of big avalanche activity on the Bow Hut approach today. Fresh size 2 avalanche over the trail, and a very large (estimated size 3.5) deep slab from the Vulture Glacier ran over the Bow Hut headwall and covered the trail through the moraines. These are our only reports from today, but they indicate that large avalanches remain very likely.

Confidence

Problems

Persistent Slabs

Several buried weak layers in the middle and lower parts of the snowpack have become reactive again as they have been overloaded by recent snow and rain. Large avalanches are reaching historical run outs and crossing valley bottom trails.

Be wary of slopes that did not previously avalanche.
Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

3 - 4

Wind Slabs

Wind slabs over 1m deep exist at higher elevations and at ridge crests near tree line. These slabs are still reactive in tests and could produce avalanches. Cornices have also grown significantly and are fragile. Avoid areas with wind effect.

Pay attention to overhead hazards like cornices which could easily trigger persistent slabs.
If triggered the storm/wind slabs may step down to deeper layers resulting in large avalanches.

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

2 - 3

Loose Wet

With warming temperatures we may start to see loose wet avalanches at lower elevations and on steep solar aspects over the next couple of days. Watch for clues like snowballing that indicate that the snow surface is warming.

Use extra caution on slopes if the snow is moist or wet.
If triggered the loose wet sluffs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Mar 23rd, 2017 4:00PM