Avalanche Forecast

Issued: Mar 21st, 2017 3:47PM

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.

mgrist, Avalanche Canada

Cariboos.

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.WEDNESDAY: 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 1300mFRIDAY: Isolated flurries (local amounts 5-10cm possible) / Light to moderate southwest wind / Freezing level 1500m

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 and wind slabs from the weekend to continue to be reactive at upper elevations, especially if the sun comes out in full force. Occasional cornice fall has also triggered large slabs.Disciplined travel is essential: Carefully manage your exposure and stick to conservative terrain.

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 wind slabs (or soft slabs) at treeline and above. Below 1900m, the new (moist) 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

Wind Slabs

Look for changes in the snow as you climb up through the elevation bands - shooting cracks, denser snow, hollow sounds and cornices above are all good indicators of wind loading.

Be careful with wind loaded pockets, especially near ridge crests and roll-overs.If triggered, the wind slabs may step down to deeper layers resulting in large avalanches.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

Persistent weakness layered throughout the snowpack create the potential for very large step-down avalanches. Heavy loads such as a smaller storm/wind slab avalanche or even a cornice failure will increase the likelihood of triggering these layers.

Avoid or use extreme caution around thin snowpack areas.Be aware of the potential for large, deep avalanches due to the presence of buried weak layers.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

2 - 4

Valid until: Mar 22nd, 2017 2:00PM