Avalanche Forecast

Issued: Jan 19th, 2017 4:51PM

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

Avalanche Canada shorton, Avalanche Canada

Uncertainty about deep persistent slabs warrants a conservative approach to terrain after the storm.

Summary

Confidence

Moderate - Due to the number of field observations

Weather Forecast

FRIDAY: Cloudy, light southwest winds, freezing level dropping with alpine temperatures around -5 C.SATURDAY: Cloudy with isolated flurries, moderate southeast winds, alpine temperatures around -8 C.SUNDAY: Cloudy with sunny periods, light southeast winds, alpine temperatures around -8 C.

Avalanche Summary

On Wednesday, several loose wet avalanches were reported from steep rocky terrain at lower elevations where rain fell on snow. Storm slabs sitting on a weak layer of surface hoar and/or a crust are likely easy to trigger at higher elevations. Full depth avalanches continue to be a concern due to the weak faceted snowpack below old hard wind slabs. This deep persistent weak layer may take prolonged warm weather with consistent snowfall to settle and bond.

Snowpack Summary

20-25 cm of new storm snow has been transported by southwest winds and now sits on a mix of old surfaces left behind after the recent cold and windy weather. Expect the new storm snow to bond poorly where it is sitting on a weak layer of buried surface hoar and/or a hard old wind polished surface. The freezing level recently reached 1000 m, and below this level the snowpack is likely moist and will eventually form a hard crust. Most areas continue to have a shallow and weak snowpack that is about 120-150 cm at treeline. In general, the snowpack above treeline has been heavily wind effected; this has resulted in hard wind slabs above weak faceted snow.

Problems

Deep Persistent Slabs

An icon showing Deep Persistent Slabs
Recent storm snow combined with warming and wind has loaded hard slabs above a weak faceted base. Uncertainty revolves around what type of load is now required to trigger these deep persistent slabs.
Be aware of the potential for full depth avalanches due to weak layers at the base of the snowpack.Stick to simple terrain and be aware of what is above you at all times.Avoid slopes with convexities or variable snowpack depths. Thin weak spots are likely trigger points

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 3

Storm Slabs

An icon showing Storm Slabs
Recent snow, warming, and strong winds have created a widespread storm slab problem, particularly on wind-loaded features. Storm slab avalanches in motion may step down and trigger deep persistent slab avalanches.
The new snow will require several days to settle and stabilize.If triggered the storm slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Jan 20th, 2017 2:00PM

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