Avalanche Forecast

Issued: Mar 9th, 2018 4:05PM

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

mbender, Avalanche Canada

Sea To Sky.

Expect to see clear skies and rising freezing levels through the weekend into next week. This will initially impact the surface snow especially on solar aspects.

Summary

Confidence

High -

Weather Forecast

SATURDAY: Mix of sun and cloud / light south wind / Alpine temperature -3 / Freezing level 1400m SUNDAY: Mix of sun and cloud / Light to moderate south wind / Alpine temperature 1 / Freezing level 2000m MONDAY: Mix of sun and cloud / Light south wind / Alpine temperature 5 / Freezing level 2500m

Avalanche Summary

On Friday there were reports of a several explosives triggered storm slab avalanches size 1.5-2Â that entrained the storm snow only on a variety of aspects.Â There were also explosives controlled cornice releases to size 1.5. Reports from Tuesday included a small wind slab on a northwest aspect in the McBride Range stepped down and triggered a much larger persistent slab avalanche when it reached 1900 m. The result was a size 3 avalanche (100 cm thick) that propagated across the entire bowl and ran all the way to the bottom of the valley. A few smaller size 1 natural slabs were also observed at and below treeline.

Snowpack Summary

Recent new snow has been redistributed by by strong west and south winds. This new snow sits on a sun crust on steep south-facing slopes, cold dry snow on northerly aspects, and wind affected snow at upper elevations.Last week's storms buried a weak layer composed of soft facets, surface hoar, and/or crust that is roughly 50-100 cm below the surface. This layer has produced whumpfing, sudden results in snowpack tests, and some remotely triggered avalanches. Lots of the activity has been on buried surface hoar on north aspects at upper treeline elevations. The snowpack is well settled and strong beneath this interface. 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

Persistent Slabs

A layer of surface hoar, sugary facets, and/or crust is buried 50-100 cm deep and has produced widespread whumpfing, concerning snowpack test results, and a few large remotely triggered avalanches. Upper treeline elevations are the greatest concern.

Use conservative route selection while travelling at treeline elevations.Avoid open slopes and convex rolls at treeline where buried surface hoar may be preserved.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1.5 - 2.5

Storm Slabs

Recent snow and southwest winds have built storm and wind slabs. Expect to see loose wet avalanches as the sun comes out and the freezing level rises.

Extra caution needed around cornices with current conditions.Be cautious as you transition into wind affected terrain.If triggered the storm slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Mar 10th, 2018 2:00PM