Avalanche Forecast

Issued: Mar 16th, 2018 4:56PM

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

cgarritty, Avalanche Canada

Sea To Sky.

Maintain elevated caution around lingering wind slabs, looming cornices, and during the daily cycle of loose wet avalanche conditions.

Summary

Confidence

High -

Weather Forecast

Saturday: Mainly sunny. Light east winds. Freezing level to 1500 metres with alpine high temperatures of -4.Sunday: Cloudy with isolated flurries and a trace of new snow. Light southwest winds. Freezing level to 1200 metres with alpine high temperatures of -5.Monday: Mainly cloudy. Light west winds. Freezing level to 1300 metres with alpine high temperatures of -4.

Avalanche Summary

Reports from Thursday included two recent natural storm slab releases in the Whistler area. One was a thin size 1.5 that released on a steep slope just below a ridge crest and the other is a more concerning size 3.5 that was seen on the Cheakamus Glacier from Whistler. We don't have details on the failure plane of this second release, but it may have run on the mid-February crust that was widely active about a week ago.Monday's reports included observations of three natural size 2.5 loose wet avalanches that released from steep, rocky, south-facing slopes in the afternoon in the Whistler area.

Snowpack Summary

A new crust exists on the surface on solar aspects at all elevations while new surface hoar has begun to form on shaded and sheltered higher elevations. Below the surface, a wind-redistributed 5-20 cm of new snow from a mid-week storm overlies a crust on all but high elevation north aspects, where it has buried dry, wind redistributed snow from last week's storms. Last week's storms buried a weak layer composed of soft facets, surface hoar, and/or crust found roughly 50-100 cm below the surface. A week ago this layer was producing whumpfing, sudden results in snowpack tests, and even some remotely triggered avalanches. Much of this activity was attributed to buried surface hoar on north aspects at upper treeline elevations. This buried weak layer is a limited but lingering concern in a snowpack that is otherwise well settled and strong beneath this interface. Variable winds in the past month have built up cornices on many ridgelines. They will become touchier as daily temperatures rise and when they are subject to the strong late-winter sun on clear days.

Problems

Wind Slabs

Wind slabs still linger on north aspects at higher elevations. On sheltered slopes, slabs may overlie a more reactive layer of surface hoar. South aspects are an additional daily concern as sun and warming set up loose wet avalanche conditions.

Watch for wind-loaded pockets around ridgecrests and in the lee of exposed terrain features.Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.Give cornices a wide berth while on or below ridges. Cornice falls may trigger large avalanches.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Mar 17th, 2018 2:00PM