Avalanche Canada cgarritty, Avalanche Canada

South Rockies Avalanche Forecast

Mar 24th, 2020 4:00PM

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

Forecast confidence is low due to a lack of field observations. New and reactive wind slabs should be expected in higher elevation terrain.

Summary

Confidence

Low - Uncertainty is due to the limited number of field observations.

Weather Forecast

Tuesday night: Mainly cloudy with possible isolated flurries. Light to moderate west winds.

Wednesday: A mix of sun and cloud with possible isolated flurries. Light west winds. Alpine high temperatures around -8.

Thursday: Sunny. Light to moderate west winds. Alpine high temperatures around -6.

Friday: A mix of sun and cloud. Light to moderate west or southwest winds. Alpine high temperatures around -5

Avalanche Summary

A few small (size 1) loose wet avalanches were observed in the region on Monday when the sun poked through the clouds. 

Looking forward, wind slab activity may increase as continuing light snowfall and increased wind form new slabs.

Snowpack Summary

Continuing light snowfall and elevated southwest wind are expected to form new wind slabs in exposed terrain. The new snow will sit on a melt-freeze crust on sun-exposed slopes or previously wind-affected snow, so new slabs may take some time to bond to the snowpack.

A layer of faceted grains overly a melt-freeze crust from early February. This layer currently sits 40 to 80 cm below the surface. 

The base of the snowpack contains basal facets that are most prominent in shallow, rocky start zones.

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
  • Make conservative terrain choices and avoid overhead hazard.

Problems

Wind Slabs

An icon showing Wind Slabs

Likelihood

Possible-Likely

Expected Size

1 - 2

Wind slabs are expected to form as light snowfall continues with elevated west and/or southwest wind. Increase your caution in exposed terrain, particularly in lee slopes near ridges.

Aspects:

North, North East, East, South East, South, North West.

Elevations:

Alpine, Treeline.

Deep Persistent Slabs

An icon showing Deep Persistent Slabs

Likelihood

Unlikely-Possible

Expected Size

2.5 - 3.5

Weak snow at the bottom of the snowpack hasn't gone away. Evidence of deep persistent slab avalanches has been focused in the Sparwood-Elkford area over the past month. Human triggering is most likely around steep, rocky terrain features or anywhere the snowpack is thin and weak. A failing cornice could initiate a deep persistent slab when it impacts the slope below.

Aspects:

All aspects.

Elevations:

Alpine, Treeline.

Valid until: Mar 25th, 2020 5:00PM