Avalanche Forecast

Issued: Mar 2nd, 2023 4:00PM

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

rgoddard, Avalanche Canada

South Coast, North Shore, Sasquatch, Sky Pilot, Tetrahedron.

More snow today will add to our region's reactive storm slabs and dry loose problem.

Storm slab reactivity may persist for longer than typical, due to the weak surface they are sitting on. Human triggering remains likely.

Summary

Confidence

Moderate

Avalanche Summary

On Tuesday, a few natural storm slab avalanches were reported at treeline and below treeline elevations up to size 2. Most of the slabs were 30 cm deep with one significant one being 60 cm deep. Skier-controlled dry loose avalanches were easily triggered up to size 1 from steep terrain features on all aspects.

Last weekend, a widespread natural cycle occurred throughout the region. Reports came in of very touchy human-triggered storm slabs (size 1 to 2) averaging 30 to 60 cm deep and up to 100 cm deep in wind-loaded areas.

Storm slab reactivity is expected to persist for longer than is typical due to the weak surface they are sitting on.

Check out last Friday's North Shore Snowpack Update for a picture of the unusual snowpack setup leading into last weekend's storm.

Snowpack Summary

By the end of the day Friday we could see up to 15 to 20 cm of snow accumulation. Since last weekend 70 to 90 cm of low-density snow has blanketed our region. The recent cold temperatures have kept the snow mostly dry and unconsolidated, however, storm slabs will likely be more reactive with the additional load from wind, rising temperatures, and more snow. The recent snow will likely have a poor bond to the underlying old snow surfaces. This interface consists of weak faceted snow, old hard wind slabs, and a crust between 1100 and 1600 m.

The mid and lower snowpack is well-settled, strong, and consolidated.

Snowpack depths are reaching 250 cm at treeline.

Weather Summary

Thursday Night

Cloudy, 5 cm accumulation ending by midnight, winds west 35 km/h, freezing level going down to 500 m.

Friday

Cloudy, 10 to 15 cm accumulation with most intense snowfall late in the day and continuing into the evening, winds southwest 20 to 55 km/h, freezing level around 500 m.

Saturday

Cloudy, 10 to 15 cm by morning with another 10 to 15 throughout the day, winds southeast 20 km/h, freezing level climbing to 900 m.

Sunday

A mix of sun and cloud, trace accumulation, winds east southeast 10 to 30 km/h, freezing level to 1200 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.
Storm slab size and sensitivity to triggering will likely increase through the day.
Keep your guard up at lower elevations. Storms slabs have been reactive at all elevations.
Loose avalanches may start small but they can grow and push you into dangerous terrain.

Problems

Storm Slabs

More snow and strong winds will build touchy storm slabs. The recent storm slab is averaging 40 to 60 cm deep and up to 100 cm deep in wind-loaded areas may have bonded poorly to the underlying surface.

Storm slab reactivity is expected to persist for longer than is typical, particularly in areas where slabs are sitting on a weak layer of facets and/or a crust.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 2

Loose Dry

In areas where the recent storm snow lacks cohesion, dry loose avalanches will be likely from steep terrain features. Avoid areas with terrain traps like gullies and cliffs.