Avalanche Forecast

Issued: Mar 1st, 2018 3:00PM

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 ghelgeson, Avalanche Canada

Wednesday night's storm produced 20 to 45 cm with east/southeast wind which has likely formed storm slabs in unusual locations. Keep a close eye on the effects of the strong sun Friday, it could initiate natural avalanche activity very quickly.

Summary

Confidence

Low - Timing or intensity of solar radiation is uncertain on Friday

Weather Forecast

There is potential for a few more centimeters of snow on Friday, and then we move into a high and dry period. No significant precipitation is expected for the foreseeable future. FRIDAY: A few clouds in the morning, cloud building throughout the day, freezing level rising to around 900 m, light east/northeast wind, a few cm of snow possible. SATURDAY: A few clouds, freezing level rising to around 1100 m, light northeast wind, no precipitation expected.SUNDAY: A few clouds, freezing level rising to around 1200 m, light west wind, no precipitation expected.

Avalanche Summary

On Wednesday soft wind slabs up to 20 in depth were sensitive to human triggering to size 1.5.  Wednesday night's storm likely initiated a cycle of natural storm slab avalanche activity.Small storm and wind slabs were sensitive to skier triggering Tuesday. Numerous skier triggered size 1 avalanches were reported from north and northeast facing features between 1450 m and 1900 m. We received a great MIN report of a large snowmobile triggered wind slab avalanche on the Brandywine Glacier that featured a 100 cm crown. More details available here.On Monday natural wind and storm slab avalanches to size 2.5 were observed on east/southeast facing slopes around 2000 m. A size 1.5 wind slab was skier triggered on an east facing alpine feature near ridgetop. A second storm slab was skier triggered on a northeast/east facing slope at 1900 m. Unsupported rolls at treeline were also sensitive to ski cuts producing very soft slabs 30 to 70 cm in depth.

Snowpack Summary

The Wednesday night storm produced far more snow than expected, 20 to 45 cm fell across the region accompanied by winds out of the east, southeast and south. In wind exposed terrain the new snow rests on widespread wind damaged snow and wind slabs that were formed by the weekend snow and strong to extreme winds earlier this week out of the southeast, south and southwest. In wind sheltered terrain the new snow may be sitting on a thin layer of surface hoar. The February 22nd interface is now down 50 to 70 cm, this layer is composed of old wind slabs, spotty surface hoar, facets and a sun crust on solar aspects. Snowpack testing on Wednesday continues to produce planar shears at this interface. As we move towards the weekend south facing slopes will be the most suspect with regard to this layer. Beneath the February 22nd interface the snowpack is well settled and strong. Variable winds in the past month have produced cornices on many ridgelines. They will become touchier as they grow in size, as temperatures rise, and when they are subject to the strong late-winter sun on clear days.

Problems

Storm Slabs

An icon showing Storm Slabs
20 to 45 cm of snow fell Wednesday night with strong wind, watch for wind and storm slabs in unusual locations. The recent storm snow is hiding wind slabs formed earlier this week. Periods of sun Friday may initiate natural storm slab avalanches.
Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.Caution with south facing slopes, periods of sun could quickly induce natural storm slab avalanches.Start with simple terrain and slowly step out as you gather information about the new snow.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 2.5

Cornices

An icon showing Cornices
Large cornices have formed along many ridgelines. Cornices are inherently unstable, unpredictable, and demand respect, especially when the sun is out.
Firm cornices may pull back into flat terrain at ridgetop if they fail.Give cornices a wide berth when traveling on or below ridges.Avoid slopes when the solar radiation is strong, especially if they have large cornices overhead.

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

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 3

Valid until: Mar 2nd, 2018 2:00PM