Avalanche Canada ahanna, Avalanche Canada

South Rockies Avalanche Forecast

Mar 22nd, 2020 4:00PM

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

Cloud cover and flurries may temper daytime warming. Minimize exposure to cornices and continue to avoid thin, rocky start zones.

Summary

Confidence

High -

Weather Forecast

Sunday night: Increasing cloud. Moderate to strong southwest wind. Freezing level 1200 m.

Monday: Scattered flurries bringing trace. Moderate to strong southwest wind. Freezing level 1800 m.

Tuesday: 5-15 cm new snow. Light southwest wind. Freezing level 1000 m.

Wednesday: 5-10 cm new snow. Light southwest wind. Freezing level 1200 m.

Avalanche Summary

Loose wet avalanches were observed on solar aspects during the previous warm, sunny week. A single snowmobile triggered size 1 wind slab was observed amid extensive slope "testing" on Friday. In neighboring Waterton National Park, a size 2 deep persistent slab out of steep, thin, rocky alpine terrain Thursday reminds us that the basal facets still exist and can be triggered in this type of terrain. 

If you decide to travel in the backcountry, consider sharing your observations with us and fellow recreationists via the Mountain Information Network (MIN) to supplement our data stream as operators are shutting down. Even just a photo of what the day looked like would be helpful.

Snowpack Summary

A dusting of up to 10 cm of new snow sits over melt-freeze crusts on solar aspects, and extensively wind affected surfaces in exposed terrain that did not see the sun. Surface hoar was observed on these old surfaces before they were buried, mostly on shady aspects.

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

  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.
  • Be aware of the potential for large avalanches due to the presence of a deep persistent slab.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.

Problems

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 23rd, 2020 5:00PM