Avalanche Canada cgarritty, Avalanche Canada

South Rockies Avalanche Forecast

Mar 25th, 2020 4:00PM

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

Limited observations are keeping forecast confidence low. Recent snow is expected to remain reactive to triggering on Thursday.

Summary

Confidence

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

Weather Forecast

Wednesday night: Becoming clear. Light northwest winds.

Thursday: Sunny with cloud developing in the afternoon. Light to moderate west winds. Alpine high temperatures around -5.

Friday: Mainly cloudy. Light to moderate west or southwest winds. Alpine high temperatures around -5

Saturday: Mainly cloudy. Light to moderate southwest winds. Alpine high temperatures around -4.

Avalanche Summary

No new avalanches were reported from Tuesday's storm, but observations have been minimal. The new snow is expected to remain reactive over the near term, especially on steeper south facing slopes and in areas where wind loading has occurred or will occur.

Snowpack Summary

About 15-25 cm of new snow accumulated during Tuesday's storm. The new snow likely sits above a melt-freeze crust on sun-exposed slopes and on previously wind-affected snow in other areas, so new slabs may take some time to bond to these surfaces.

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.
  • Minimize exposure to sun-exposed slopes when the solar radiation is strong.

Problems

Wind Slabs

An icon showing Wind Slabs

Likelihood

Possible-Likely

Expected Size

1 - 2

Increasing southwest winds are expected to move Tuesday's snow into new wind slabs on leeward slopes, particularly near ridgetop.

Aspects:

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

Elevations:

All elevations.

Loose Wet

An icon showing Loose Wet

Likelihood

Likely

Expected Size

1 - 2

New snow accumulations exposed to strong sunshine will be increasingly likely to shed from steep slopes on Thursday. This may occur naturally or with a human trigger.

Aspects:

South, South West.

Elevations:

All elevations.

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 26th, 2020 5:00PM