Avalanche Forecast

Issued: Feb 7th, 2018 4:50PM

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

Avalanche Canada swerner, Avalanche Canada

The snowpack is complex with buried weak layers being overloaded by recent storm snow. Travel in avalanche terrain is not recommended.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain

Weather Forecast

Thursday: New snow 10-25 cm by early afternoon. Ridgetop winds strong from the southwest. Alpine temperatures near -5 with freezing levels 1600 m. Friday: Mix of sun and cloud with alpine temperatures near -10 and freezing levels at valley bottom. Ridgetop winds light from the north.Saturday: Mostly clear with no forecast snow. Alpine temperatures near -10 and ridgetop winds light from the northeast.

Avalanche Summary

On Tuesday, a couple of natural wind slab avalanches up to size 2.5 from east aspects above 2000 m were reported. Avalanche control, using explosives also triggered numerous persistent slab avalanches up to size 2.5. These were mostly from N-SW aspects above 1900 m. One of these large avalanches stepped down to ground in some places on a early season November crust. With forecast snow and strong winds expect large natural avalanche activity to continue through the forecast period.

Snowpack Summary

Up to 20 cm of new storm snow accompanied by strong winds adds stress to the upper snowpack. This now brings 90-140 cm of settled snow over two surface hoar/ crust layers that were formed early to mid-January. Digging deeper 160-200 cm sits the mid-December surface hoar layer. All of these persistent weak layers lurk within the snowpack and continue to be reactive, producing large and destructive avalanches. Near the base of the snowpack exists a crust/ facet interface which could be triggered by a step down avalanche, cornice failure, thin to thick spot triggering by people or reaching its threshold with new load from above. The snowpack is extremely complex and requires respect and diligence at this time.

Problems

Storm Slabs

An icon showing Storm Slabs
New storm slabs will be reactive and could step down to deeper layers initiating large and destructive avalanches.
Avoid all avalanche terrain during periods of heavy loading from new snow and wind.Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Very Likely - Certain

Expected Size

1 - 3

Persistent Slabs

An icon showing Persistent Slabs
The snowpack is complex and continues to produce very large avalanches on several weak layers buried below the surface.
Be mindful that deep instabilities are still present and have produced recent large avalanches.Minimize overhead exposure; avalanches may reach the end of run out zones.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

2 - 4

Valid until: Feb 8th, 2018 2:00PM