Avalanche Forecast

Issued: Mar 15th, 2016 9:45AM

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

triley, Avalanche Canada

Kootenay Boundary.

Recent storm slabs continue to be a concern for human triggered avalanches. Storm slabs or cornices in motion may step down to the deeply buried persistent weak layer resulting in large destructive avalanches.

Summary

Confidence

Moderate - Timing or intensity of solar radiation is uncertain

Weather Forecast

Some chance of convective flurries overnight with moderate west or northwest winds and freezing levels down to valley bottoms. A mix of sun and cloud on Wednesday with some lingering flurries, moderate westerly winds and daytime freezing levels climbing up to 1500 metres. Mostly sunny on Thursday with light winds and a good overnight freeze; daytime freezing levels up to 1500 metres. Clear on Friday with a good overnight freeze, light winds and daytime freezing levels climbing up to 1700 metres.

Avalanche Summary

On Monday there was an avalanche in the Mt Mackie area southwest of Castlegar that resulted in a fatality. We have limited information about the size and sliding layer at this time. We will release more information when it becomes available. There was also a skier accidental size 2.5 that started as a cornice failure and propagated down to one of the buried crusts; this was near Red Mtn in the Rossland range. There were also a couple of natural avalanches and a skier accidental avalanche size 2.0 in the eastern part of the region near Nelson. The storm snow continues to be a concern for human triggering, and avalanches that start in the storm snow may "step-down" to deeper buried weak layers. Cornices are also a concern for natural avalanches and human triggering.

Snowpack Summary

There is now 25 to 50 cm of storm snow combined with moderate southwest winds which have likely created deep wind slabs on the leeward side of ridgecrests and mid-slope terrain features. In some drainages these storm slabs may be sitting on a thin crust that was initially buried on March 11th. A second curst, (the early March melt/freeze crust) can be found down 50 to 80 cm. A persistent weak layer buried late-February is typically down 60 to 100 cm and remains sensitive to triggering as indicated by recent avalanche activity. This weakness is widespread buried surface hoar on sheltered slopes above 1700 m, and a crust potentially with associated facets on previously sun-exposed slopes (primarily south aspects).

Problems

Storm Slabs

Storm slabs continue to be a concern for human triggering. Strong solar radiation over the next few days may increase the likelihood of triggering. Storm slab avalanches may step down to deeply buried weak layers.

Choose well supported conservative lines and watch for clues that indicate instability.>Avoid freshly wind loaded features.>Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 4

Persistent Slabs

The deeply buried late February surface hoar may continue to allow for human triggering with large loads like a group of skiers or a snowmobile. Cornice falls or storm slab avalanches in motion may step down to the deeply buried persistent weak layer

Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar. >Surface avalanches in motion could step down and initiate persistent slab avalanches which have the potential to be large and destructive.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

3 - 5

Valid until: Mar 16th, 2016 2:00PM