Avalanche Forecast

Issued: Feb 17th, 2016 8:26AM

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

Avalanche Canada rbuhler, Avalanche Canada

Storm slabs continue to develop at higher elevations and will be reactive to human-triggering on Thursday. Conservative terrain choices remain critical and it is important to continually assess conditions as they change throughout the day.

Summary

Confidence

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

Weather Forecast

Active weather continues on the Thursday with the next storm front arriving Wednesday overnight. Another 15-30cm is forecast between Wednesday night and Thursday afternoon. Amounts are forecast to be greatest to the south of the region. Alpine winds are expected to be moderate to strong from the southwest and freezing levels are forecast to fall to around 1200m on Thursday. Snowfall is expected to continue on Friday and models are currently showing 5-10cm. Alpine winds are expected to stay moderate to strong from the south to southwest and freezing levels are expected to fluctuate between 1000 and 1500m. Light snowfall is currently forecast to continue on Saturday morning but conditions are expected to clear off as a ridge of high pressure approaches.

Avalanche Summary

On Tuesday, three size 1.5 storm slab avalanches were ski cut on north aspects at 1600m elevation. These slabs were 15-25cm thick and were released on convex roll features. A skier accidently triggered a size 1 storm slab avalanche on a north aspect at 1800m elevation. A few natural size 1.5 avalanches were reported on a west aspect at 2000m and were around 20cm thick. Several solar triggered loose avalanches were also reported from steep sun exposed slopes in the alpine and at treeline. No new avalanches were reported on Monday. On Sunday, a natural size 3 wind slab avalanche was reported. The slab was 50cm thick and ran on an old reloaded bed surface in a shallow snowpack area. Storm slab avalanches are expected to be remain reactive to human-triggering at higher elevations with ongoing snowfall and wind continuing Thursday. Cornices are reported to large and fragile, and may fail under the weight of a person.

Snowpack Summary

40-80cm of new snow has accumulated in the last week and overlies a thick melt-freeze crust which extends into the alpine. The snow is reported to be bonding well to the crust and recent avalanches have been failing within the recent storm snow, not on the crust interface. At treeline and below, other crusts may exist in the upper snowpack due to the recently fluctuating freezing levels. Freezing levels on Wednesday climbed to around 2000m and are expected to fall to around 1200m on Thursday so a new crust can be expected in the upper snowpack as rain changes to snowfall. Ongoing southeast through southwest winds have been loading leeward features in the alpine and large cornice development has been reported over the last few days. The weak surface hoar layer from early January can be found down over a meter and is still reactive in isolated snowpack tests but triggering an avalanche on this layer has become unlikely.

Problems

Storm Slabs

An icon showing Storm Slabs
Widespread storm slabs continue to develop in higher elevation terrain and are expected to be quite reactive on Thursday.  Extra caution is required on north through east aspects in the alpine where wind loading has increased slab reactivity.
The new snow will require a couple days to settle and stabilize. >Avoid freshly wind loaded features. >Avoid avalanche terrain during periods of heavy loading from new snow, wind, or rain.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 3

Cornices

An icon showing Cornices
Looming cornices could collapse, especially during storms or during warm weather.  The weight of a person may be enough to cause a cornice failure.
Extra caution needed around cornices with current conditions.>Give cornices a wide berth when travelling on or below ridges.>

Aspects: North, North East, East, South East.

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 4

Valid until: Feb 18th, 2016 2:00PM