Avalanche Forecast

Issued: Mar 19th, 2021 4:00PM

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

Avalanche Canada cgarritty, Avalanche Canada

Steady snowfall and elevated winds are keeping winter alive up high. Be ready to manage a typical array of wind slab and cornice hazards as you gain elevation. Push danger ratings a step higher if you're closer to Bear Pass than Shames.

Summary

Confidence

Moderate -

Weather Forecast

Friday night: Cloudy with continuing scattered flurries bringing up to 5 more cm of new snow. Moderate to strong west or northwest winds.

Saturday: Cloudy with a stronger storm pulse starting with a trace of new snow then increasing quite a bit overnight. Moderate west or southwest winds becoming extreme south overnight. Alpine high temperatures around -8.

Sunday: Cloudy with continuing flurries bringing an uncertain 5-15 cm of new snow, closer to 10-30 cm with overnight accumulations. Extreme south winds easing to light southwest in the afternoon. Alpine high temperatures around -6.

Monday: Cloudy with isolated flurries. Light southwest winds. Alpine high temperatures around -5.

Avalanche Summary

Observations from the last couple of stormy days are still limited, however a MIN report from Thursday in the Shames area paints a clear picture of slab reactivity in specific wind loaded features. Similar conditions should persist through Saturday as new snow and wind continue to form surface instabilities.

A natural wind slab avalanche cycle with numerous wind slabs from size 2 to 3.5 (large to very large) was reportedly ongoing in the Bear Pass area on Wednesday morning and again on Friday morning. Natural wet loose and glide avalanches have accompanied this activity below about 900 metres. 

Snowpack Summary

Light new snow amounts will continue to accumulate through Saturday afternoon when a stronger storm pulse begins to move into the region. Elevated winds will likely continue to forming fresh slabs in lee features at treeline before a more widespread storm slab problem forms over Saturday night. Incremental snowfall over the past week added to storm totals from last weekend ranging from 50 cm in the north to 150 cm in the south of the region. Rain fell below 900 m during that storm, saturating the upper snowpack at lower elevations.

Collectively, our new snow and recent storm snow may overlie a persistent weak layer of surface hoar buried March 12 on sheltered northerly aspects around treeline or a melt-freeze crust on southerly aspects and below treeline.

Around 100 to 300 cm now overlies a persistent weak layer buried in mid-February that may still be a concern in isolated parts of the region. The layer consists of surface hoar in areas sheltered from the wind and facets that formed during February's cold snap. 

Conditions are lending themselves to these persistent layers stabilizing, but professionals in the region are continuing to track and treat them with caution, especially the shallower layer from March.

The mid and lower snowpack is well settled and strong in most areas.

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Choose conservative terrain and watch for clues of instability.
  • Make observations and assess conditions continually as you travel.

Problems

Wind Slabs

An icon showing Wind Slabs

A bit more snow and shifting wind are likely to continue forming fresh wind slabs over more stubborn older slabs on Saturday. Although new wind slabs are the main issue, keep your guard up in steep sheltered terrain. Recent accumulations may be sitting on a weak layer of surface hoar on north aspects or a crust on solar aspects and lower elevations.

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

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 2.5

Valid until: Mar 20th, 2021 4:00PM