Avalanche Forecast

Issued: Feb 28th, 2018 4:56PM

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

Avalanche Canada ghelgeson, Avalanche Canada

This forecast is based around 6 to 25 cm of snow arriving Wednesday night with strong southerly winds, but the track of the storm is very difficult to pin down. Seek out wind sheltered terrain to avoid the wind slab problem and find the best riding!

Summary

Confidence

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

Weather Forecast

After much uncertainty, the models have converged on a solution that is more of a glancing blow than direct hit, but the Sea to Sky should get a significant re-fresh Wednesday night though Thursday. It looks like we will be entering a high and dry period after this system passes through. WEDNESDAY NIGHT: Freezing level around 600 m, 6 to 25 cm of snow, strong to extreme south wind.THURSDAY: Broken cloud cover, freezing level rising to around 1000 m, light to moderate south/southeast wind, 2 to 10 cm of snow possible. FRIDAY: Clear skies in the morning, cloud building throughout the day, freezing level around 800 m, light variable wind, no precipitation expected.SATURDAY: A few clouds, freezing level around 1000 m, light variable wind, no precipitation expected.

Avalanche Summary

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

Storm totals from the weekend are between 25 and 55 cm. This snow was subject to strong to extreme winds out of the southeast, south and southwest on Sunday, Monday and Tuesday which has formed widespread wind slabs that extend down to treeline. The new snow rests on the February 22nd interface which consists of old wind slabs, spotty surface hoar, facets and a sun crust on solar aspects. Snowpack testing on Tuesday continues to produce resistant planar shears at this interface which makes sense given the activity listed above. 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
Strong wind over the last 72 hours has formed wind slabs that may remain sensitive to human triggering. New snow and strong south wind are expected to form fresh slabs throughout the day Thursday too.
Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.Avoid wind loaded terrain features, especially during periods of active loading.Seek out wind sheltered terrain below treeline.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2.5

Valid until: Mar 1st, 2018 2:00PM

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