Avalanche Forecast

Issued: Jan 18th, 2023 4:00PM

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

Avalanche Canada swerner, Avalanche Canada

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Continue to make conservative terrain choices and consider the consequences of an avalanche on a chosen slope. Regroup in safe locations, space out, and avoid shallow rocky start zones.

Summary

Confidence

Moderate

Avalanche Summary

On Tuesday, operators across the region used explosives on a wide range of slopes (aspect and elevations). Explosives produced several smaller storm slabs avalanches, however, the most concerning events were the numerous size 2.5- 3 deep persistent slabs that released down deep on the basal facets to the ground. This suggests that a large enough load could possibly initiate one of these deep avalanches or even a lighter load from a thin spot (rocks, thin to-think areas) in the snowpack.

On Monday, A few small (size 1 to 1.5) human-triggered slabs were reported, mostly failing on a 30 cm deep surface hoar layer. A few larger (size 2) human-triggered slabs were reported in the Esplanade range. Explosive avalanche control produced multiple large (size 2) and one very large (size 3) deep persistent slab.

Last Saturday, a skier triggered a size 2.5 avalanche on a low-angle alpine slope near Golden. This avalanche had a 1 m crown and ran on the facets near the bottom of the snowpack.

Snowpack Summary

10 to 20 cm of settled storm snow can be found in sheltered areas, while open terrain has been wind affected. A rain crust can be found up to 2000 m in most parts of the region.

There are two concerning weak layers in the top meter of the snowpack. The first is a layer of surface hoar from early January and the second is a layer of surface hoar, facets, and a crust from December. Both these layers are most concerning at treeline and above. The bottom of the snowpack sees weak facets that continue to produce large avalanches and will likely persist for a prolonged period of time.

In general, the snowpack is shallow and weak.

Weather Summary

Wednesday Night

Cloudy with a trace of new snow. Light to moderate southwest wind and a low of -9 C. Freezing level valley bottom.

Thursday

A mix of sun and cloud. Light to moderate northwest winds and a high of -8 C at treeline. Freezing levels at valley bottom.

Friday

A mix of sun and cloud. Ridge wind light from the West. Treeline temperatures near -6 C.

Saturday

Cloudy with some sunny periods. Flurries 5-8 cm. Ridge wind strong from the southwest with a treeline high temperature of -4 C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Be mindful that deep instabilities are still present and have produced recent large avalanches.
  • Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
  • Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
  • Uncertainty is best managed through conservative terrain choices at this time.

Problems

Persistent Slabs

An icon showing Persistent Slabs

There are two weak layers in the top meter of the snowpack that continue to produce human-triggered avalanches. The first is a layer of surface hoar down 30 to 40 cm buried in early January. The second is a layer of surface hoar, facets and/or a crust from December. This layer can be found down 40 to 70 cm.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 2

Deep Persistent Slabs

An icon showing Deep Persistent Slabs

A weak layer near the base of the snowpack, buried in November, remains a concern. Human triggering of this layer remains possible, especially in shallow areas with variable snow depths.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

Valid until: Jan 19th, 2023 4:00PM