Avalanche Canada dsaly, Avalanche Canada

South Rockies Avalanche Forecast

Mar 26th, 2020 5:00PM

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.

Limited observations are keeping forecast confidence low. Steady winds are redistributing loose snow and building wind slabs.

Summary

Confidence

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

Weather Forecast

Thursday night: Increasing cloud coverage. Alpine low temperature -9 C. Moderate west winds.

Friday: Cloudy with isolated flurries, up to 5 cm. Alpine high temperature -3 C. Moderate to strong southwest winds.

Saturday: Cloudy with scattered flurries, up to 5 cm. Alpine high temperature -5 C. Moderate gusting to strong southwest winds.

Sunday: Cloudy with scattered flurries, 5-10 cm. Alpine high temperature -1 C. Moderate gusting to strong southwest winds.

Avalanche Summary

No new avalanches were reported from Tuesday's storm, but observations have been minimal. Recent 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. Sun has encouraged settlement and produced moist slopes on steep solar aspects at lower elevations. Increasing southwest winds are redistributing loose surface snow. 

The recent new snow 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

Steady southwest winds are redistributing loose surface snow and building new wind slabs on leeward slopes, particularly near ridgetop.

Aspects:

North, North East, East, South East, 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 27th, 2020 5:00PM