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Avalanche Canada rbuhler, Avalanche Canada

South Rockies Avalanche Forecast

Jan 27th, 2016 8:23AM

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

Wind slabs continue to develop and are expected to be touchy on Thursday.Warm temperatures mean extra caution is required where smaller avalanches have the potential to step down to deeper weak layers that may still be reactive.

Summary

Confidence

Moderate - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

A pacific storm system is expected to reach the region on Thursday morning.  5-15cm of snowfall is expected on Thursday.  Freezing levels are expected to hover around 1500m during the storm and alpine winds should be strong from the southwest.  A mix of sun and cloud is expected for Friday with freezing levels around 1000m and light alpine winds.  Light snowfall is being forecast for Saturday with models currently showing around 5cm. 

Avalanche Summary

An early report from Thursday shows that explosives triggered a size 2.5 deep persistent slab avalanche on a south aspect at 2000m in the southeast of the region.  This released down 70cm on the early December crust layer.  No new avalanches were reported on Wednesday.  On Tuesday, explosives triggered a size 3 persistent slab avalanches on an east aspect at 2000m.  This released down 150cm on the early December crust layer. 

Snowpack Summary

Recent strong to extreme winds from the southwest to west have redistributed the snow at treeline and above. Wind slabs have formed on lee slopes and windward slopes are being stripped away.  Freezing levels are reported to be around 1900m on Wednesday afternoon.  The mid and lower snowpack are getting stronger and settling well with the warm temperatures.  A weak crust/facet layer from early-December is typically down over 1m.  It has become difficult to trigger this layer but it is still reactive in snowpack tests suggesting that if you are able to trigger it, the layer is capable of wide propagations and large destructive avalanches.  Recent explosive control triggered a few large avalanches on this layer in the southeast of the region.  In the northwest of the region, there may still be reactive surface hoar layers in the upper snowpack.

Problems

Wind Slabs

An icon showing Wind Slabs

Likelihood

Likely

Expected Size

1 - 3
Touchy wind slab development is expected to continue with new snowfall, strong southwest winds, and warm temperatures.
Avoid freshly wind loaded features. >Be aware of the potential for wide propagations due to the presence of hard windslabs. >Use ridges or ribs to avoid pockets of wind loaded snow. >

Aspects:

North, North East, East, South East, South.

Elevations:

Alpine, Treeline.

Persistent Slabs

An icon showing Persistent Slabs

Likelihood

Possible

Expected Size

3 - 5
Warming temperatures and new loading from wind, snow, and rain, may increase the likelihood of triggering a persistent slab avalanche. A small avalanche or a cornice failure have the potential to step-down to a deeper layer.
Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>Use extra caution on open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.>

Aspects:

All aspects.

Elevations:

Alpine, Treeline.

Valid until: Jan 28th, 2016 2:00PM