Avalanche Forecast

Issued: Feb 8th, 2017 4:22PM

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

mbender, Avalanche Canada

Northwest Inland.

Use extra caution as you transition into wind affected terrain and watch for signs of recent wind loading in leeward terrain features

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain on Friday

Weather Forecast

THURSDAY: Cloudy with sunny periods / Light to moderate southeast wind / Alpine temperature -11 FRIDAY: Mix of sun and cloud / Moderate to strong southwest wind / Alpine temperature -9SATURDAY: Cloudy with isolated flurries / Moderate to strong southwest wind / Alpine temperature -4More details can be found on the Mountain Weather Forecast.

Avalanche Summary

No new avalanches were reported in the past few days. Most recent avalanche activity was reported on the weekend. This included a remotely triggered size 2 wind slab avalanche on a southwest aspect at 1200 m elevation. The slab was 60 cm thick and was triggered from 10 m away. On Saturday, a natural size 2 wind slab avalanche was reported on a north aspect at 1600 m elevation with a slab thickness of 30 cm. On Friday, a natural size 2.5 deep persistent slab was observed in the far north of the region on a southeast aspect at 1800 m elevation which released on the ground.On Thursday, expect recently formed wind slabs to remain reactive to human triggering. Ongoing outflow winds may continue to add additional load to these wind slabs in places where there is still snow available to be redistributed. A basal weakness continues to drive a low probability/high consequence problem for the region. Very large avalanches remain possible, especially in shallow snowpack areas.

Snowpack Summary

Widespread wind affected surfaces are being reported in exposed terrain including scoured surfaces, sastrugi, and hard wind slabs. In areas sheltered from the wind, the surface snow is reported to be faceting and surface hoar is developing. Below around 1400 m elevation, a rain crust can be found near the surface of the snowpack. Deeper in the snowpack, several buried surface hoar layers can be found between 30-70 cm deep. Recent reports suggest these layers have generally stabilized but isolated weaknesses may still exist, especially where buried surface hoar is still intact. A generally stiff mid pack sits above weak sugary snow near the ground. This basal weakness woke up during the last storm and produced numerous large avalanches which released on the ground. The layer is dormant for the time being but is expected to wake up with warming, heavy loading, or by the weight of a smaller avalanche stepping down.

Problems

Wind Slabs

Recent strong to extreme outflow winds have formed hard wind slabs in leeward terrain features. These slabs are expected to remain reactive as the wind may continue to add additional load to these slabs.

If triggered the wind slabs may step down to deeper layers resulting in large avalanches.Be cautious as you transition into wind affected terrain.Be aware of the potential for wide propagations due to the presence of hard windslabs.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Deep Persistent Slabs

A weakness at the bottom of the snowpack is lingering and creating a high probability/high consequence problem. This layer may be triggered in shallow snowpack areas or by the weight of smaller avalanches.

Avoid steep convexities or areas with a thin or variable snowpack.Be aware of the potential for full depth avalanches due to weak layers at the base of the snowpack.Use conservative route selection, choose moderate angled and supported terrain with low consequence.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 4

Valid until: Feb 9th, 2017 2:00PM