Avalanche Forecast

Issued: Mar 28th, 2018 5:09PM

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

cgarritty, Avalanche Canada

Northwest Inland.

A bit of new snow and wind is set to fuel wind slab formation up high while the bond beneath our new snow remains weak. Maintain disciplined terrain selection while danger remains elevated.

Summary

Confidence

Moderate - Due to the number of field observations

Weather Forecast

Thursday: Cloudy with flurries bringing 5-10 cm of new snow, continuing overnight. Light to moderate southeast winds. Freezing level near valley bottom with alpine high temperatures around -6.Friday: Cloudy with lingering light flurries and a trace of new snow. Light southeast winds. Freezing level near valley bottom with alpine high temperatures around -10.Saturday: A mix of sun and cloud. Light to moderate southeast winds. Freezing level to 700 metres with alpine high temperatures around - 7.

Avalanche Summary

Reports from Monday included several observations of natural storm slab releases from steep east aspects in the alpine in the Howsons. Several more large (size 2) loose wet avalanches were observed in steep terrain at low elevations.Sunday's reports again included numerous observations of ski cutting producing size 1.5 storm slab releases on small rolls. These slabs were failing at an upper storm interface before stepping down to the full depth of our recent storm snow (about 40 cm). Terrain selection is likely to have limited the size of these results.On Saturday, ski cutting on convex rolls below treeline produced size 1.5 slabs in the recent storm snow down 30 cm deep. These failed over the widespread melt-freeze crust and gathered substantial mass as they traveled downslope.

Snowpack Summary

Up to 40 cm of storm snow from last week has been settling into a reactive slab over a range of old snow surfaces, including two layers of surface hoar existing on shaded aspects at high elevations as well as a melt-freeze crust on all aspects at treeline and below. This storm snow has been showing a poor bond to the shallowest of these buried weak layers, down about 40cm. Recent strong winds have redistributed the new snow into thicker and likely more reactive wind slabs on a range of aspects wind-exposed terrain.Deeper in the mid-pack, layers of crusts, facets, and isolated surface hoar buried 50 to 100 cm exist from mid- and late-February and a surface hoar/ crust layer from January is buried around 150 to 200 cm. Near the bottom of the snowpack, sugary facets exist in colder and drier parts of the region, such as in the far north.

Problems

Storm Slabs

30-40 cm of recent snow has been settling into a reactive slab over a crust in most areas as well as surface hoar on high shaded aspects. Thicker and more reactive slabs are likely to be found on north to east aspects in wind-exposed terrain.

Keep your guard up at lower elevations. Storms slabs have been reactive at all elevations.Be increasingly cautious and watch for patterns of wind loading if you enter wind-affected terrain.Watch for signs of instability like shooting cracks or recent avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 2.5

Valid until: Mar 29th, 2018 2:00PM