Avalanche Forecast

Issued: Mar 23rd, 2017 5:00PM

The alpine rating is high, the treeline rating is high, and the below treeline rating is considerable. Known problems include Storm Slabs and Loose Wet.

cgarritty, Avalanche Canada

Sea To Sky.

A warm, wet and windy storm is ramping up avalanche danger throughout the region. Expect avalanche problems to be increasing over the course of the day on Friday.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain on Friday

Weather Forecast

Thursday night: Flurries bringing 5-10 cm of new snow. Moderate to strong southeast winds.Friday: Continuing flurries bringing 10 -15 cm of new snow over the day. Moderate south winds. Freezing level to 1400 metres with alpine temperatures of -3.Saturday: Continuing flurries bringing up to 5 cm of new snow. Light southwest winds. Freezing level to 1100 metres with alpine temperatures of -6.Sunday: Mainly cloudy with isolated flurries and a trace of new snow, intensifying in the evening. Light southeast winds. Freezing level to 1300 metres with alpine temperatures of -4.

Avalanche Summary

Recent reports show observations of both natural and human triggered wind slab avalanches running to Size 1.5 in alpine and tree line lee terrain. On Friday, ongoing storm slab formation will lead to easy human triggering at the depth of new snow as well as the potential for natural avalanche activity. At upper elevations, the deeper mid-February weak layer has been trending toward a low likelihood of triggering. However, with new snow and wind loading the snowpack, it would be best to consider the potential for reactivity at this layer in your terrain selection.

Snowpack Summary

After 25 cm of new snow blanketed the region on Wednesday night, roughly 35-40 cm of new snow lies over a crust that formed over last week's storm snow. This crust exists at about 2000 metres and lower. Beneath the previous storm snow, an older rain crust that formed last week is now buried about 55-75cm deep. The mid-February crust/facet layer can still be found at the upper end of treeline and into the alpine. This interface is now 100-140 cm deep and may be over 200 cm deep in wind loaded terrain. Although there is growing uncertainty about how much longer it will remain reactive, continued caution is warranted as new snow and wind continue to load the upper snowpack and stress deeper layers.

Problems

Storm Slabs

Overnight snowfall will continue over Friday, accompanied by moderate to strong winds at higher elevations. With around 25 cm of new snow already on the surface, thick, reactive new storm slabs will be the result.

Use caution in lee areas in the alpine and treeline. Storm snow is forming touchy slabs.Be increasingly cautious as you transition into wind affected terrain.Use conservative route selection, choose moderate angled and supported terrain with low consequence.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Very Likely

Expected Size

1 - 3

Loose Wet

As freezing levels rise to around 1400 metres, expect surface snow below this elevation to become increasingly moist and likely to sluff from steep terrain, either naturally or with skier traffic.

Be cautious of sluffing in steep terrain.Avoid travelling under cliffs that are exposed to sluffing from above.Avoid traveling on ledges and cliffs where small avalanches may have severe consequences.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Likely - Very Likely

Expected Size

1 - 2

Valid until: Mar 24th, 2017 2:00PM