Avalanche Forecast

Issued: Mar 20th, 2017 4:15PM

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 mgrist, Avalanche Canada

We've weathered the storm but we're not out of the woods yet. There's a great blog post on critical factors to watch out for this spring. Click here for details.

Summary

Confidence

Moderate - Due to the number of field observations

Weather Forecast

We're looking at classic unsettled spring weather for the forecast period: cloudy with isolated (sometimes intense) flurries.TUESDAY: Isolated flurries (local amounts 5-10cm possible) / Light to moderate southwest wind / Freezing level 1500mWEDNESDAY: Broken skies with isolated flurries (local amounts 5-10cm possible) / moderate south wind /Freezing level 1600mTHURSDAY: Flurries in the morning with 5cm possible / Light east wind / Freezing level 1300m

Avalanche Summary

On Sunday we had reports of natural storm slab avalanches to Size 3 at treeline near Valemount, on a variety of aspects. On Friday skiers triggered a Size 1.5 wind slab quite low down on a slope - strong winds had transported snow farther than expected.Expect storm slabs from the weekend to continue to be reactive at upper elevations, especially if the sun comes out in full force.

Snowpack Summary

In the south of the region, we had heavy snow and strong south-west winds (gusts over 60 Km/hr) during the weekend's storm. Temperatures also warmed up significantly. The end result: widespread storm slabs and reactive wind slabs at treeline and above, with significant cornice growth as well.All this new storm snow (30- 60cm) sits on older windslabs (or soft slabs) at treeline and above. Below 1900m, the new snow sits on a melt-freeze crust from last week's warm storm, and reports so far are that the new snow is bonding well to the old crust.Approximately 100-140 cm below the surface you may find the mid-February persistent weakness. Professionals in the region have warned that the load above this layer has reached a critical amount, particularly where it presents as a crust.Deep persistent weaknesses in the lower third of the snowpack still have the potential to react to human triggers or smaller slab avalanches, especially if the sun comes out in full force.New snow totals in the north (Wells, Sugar Bowl) have been half to one-third of those in the south and avalanche danger is likely one step lower.

Problems

Storm Slabs

An icon showing Storm Slabs
Warm storm snow on Saturday and strong southwest wind created a storm slab problem. The snowpack will need time to adjust to the new load - stick to low angled terrain (with no overhead hazard) and avoid sunny slopes if/when the sun comes out.
The new snow will require several days to settle and stabilize.If triggered, the storm slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Persistent Slabs

An icon showing Persistent Slabs
Persistent weakness layered throughout the snowpack create the potential for very large step-down avalanches. The risk of triggering a deeper weak layer will be heightened while overlying storm slabs remain sensitive to human triggering.
Be aware of the potential for large, deep avalanches due to the presence of buried weak layers.Avoid or use extreme caution around thin snowpack areas.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

2 - 4

Valid until: Mar 21st, 2017 2:00PM