Avalanche Forecast

Issued: Dec 18th, 2017 4:16PM

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

Avalanche Canada istorm, Avalanche Canada

Fat wind-loaded slopes below ridge crests and convoluted rocky areas with a shallow snowpack are the two types of places where a little extra caution is a good idea.

Summary

Confidence

Low - Due to the number of field observations

Weather Forecast

Over the next few days the storm track will be aligned with the Canada USA border. The Northwest will generally be dry, clear, and with below freezing temperatures.Tuesday:  Mostly sunny, no precipitation, light to moderate northeast wind, and treeline temperatures around -10 CWednesday:  Mostly sunny, no precipitation, moderate northwest wind, and treeline temperatures a few degrees below freezing.Thursday:  Mostly sunny, no precipitation, moderate north wind, and treeline temperatures around -5 to -10 C.

Avalanche Summary

We have limited field observations to draw from so the lack of reported avalanche activity reflects both and absence of activity and survey effort.If you're out in the mountains and see recent avalanches please snap a photo and submit your information to the Mountain Information Network

Snowpack Summary

The inland region picked up 5 to 15cm of new snow over the weekend accompanied by wind that was largely out of the west, but there were periods of southeast wind recorded too. This new snow rests on a wide variety of old surfaces including small facets, crusts on solar aspects and stubborn old wind slabs near ridge crest. In protected areas below 1500m the new snow may be sitting on previously formed feathery surface hoar.Two crusts formed near the end of November are found approximately 30 to 50cm below the surface. These crusts are widespread and extend into the alpine. Previous snowpack tests produced hard results on these crusts, but we have not seen any recent information about their sensitivity to triggering. Below these crusts, a well settled mid-pack overlies the late October crust which is down near the ground. The October crust is widespread and has not been reactive to human triggering since the end of November. Average snowpack depths in the region are between 80 and 140cm at treeline, with up to 160cm in the alpine.

Problems

Wind Slabs

An icon showing Wind Slabs
Wind slabs are most likely to be found immediately lee of ridge crest and around mid-slope terrain features like rock outcroppings. While relatively small, they could be problematic in complex terrain.
Use ridges or ribs to avoid pockets of wind loaded snow.Be careful with wind loaded pockets, especially near ridge crests and roll-overs.Avoid steep convexities or areas with a thin or variable snowpack.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 2

Deep Persistent Slabs

An icon showing Deep Persistent Slabs
The late October crust lies near the base of the snowpack and while it should be gaining strength a heavy trigger in a thin rocky terrain feature may still be able to initiate a failure and subsequent large avalanche.
Be especially cautious in shallow snowpack areas, it may be possible to trigger large avalanches.Be aware of the possibility for full depth avalanches due to deeply buried weak layers.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

Valid until: Dec 19th, 2017 2:00PM

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