Avalanche Canada mconlan, Avalanche Canada

South Rockies Avalanche Forecast

Mar 23rd, 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.

There is uncertainty in the forecast due to a lack of data available at this time.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain. Uncertainty is due to the limited number of field observations.

Weather Forecast

MONDAY NIGHT: Cloudy with flurries, accumulation trace to 10 cm, moderate to strong southwest wind, alpine temperature -8 C.

TUESDAY: Cloudy with flurries, accumulation 5 to 10 cm with locally higher amounts possible, moderate southwest wind, alpine temperature -8 C, freezing level 1000 m.

WEDNESDAY: Cloudy with flurries, accumulation 5 to 10 cm, light southwest wind, alpine temperature -7 C, freezing level 1000 m.

THURSDAY: Clear skies, light southwest wind, alpine temperature -6 C, freezing level 1500 m.

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 new snowfall and wind forms fresh slabs.

Snowpack Summary

Snowfall and southwest wind are forecast for the coming days, which will form wind slabs in exposed terrain. Expect the slabs to be thickest and most reactive in lee terrain features adjacent to ridge lines. The slabs will sit on a melt-freeze crust on sun-exposed slopes or previously wind-affected snow, so these 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.
  • 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.
  • Make conservative terrain choices and avoid overhead hazard.

Problems

Wind Slabs

An icon showing Wind Slabs

Likelihood

Possible

Expected Size

1 - 2

Wind slabs will form as new snow falls with strong southwest wind. Apply added 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 24th, 2020 5:00PM