Avalanche Forecast

Issued: Feb 23rd, 2021 4:00PM

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

Avalanche Canada ahanna, Avalanche Canada

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Ease into terrain cautiously on Wednesday. Start small and look for signs of instability like shooting cracks and recent avalanches. Be mindful that sunshine can have a powerful effect on stability - and your desire to push into aggressive terrain. 

Summary

Confidence

Low - Uncertainty is due to the limited number of field observations. Recent weather patterns have resulted in a high degree of snowpack variability within the region.

Weather Forecast

TUESDAY NIGHT: Partly cloudy, light northwest wind, freezing level valley bottom.

WEDNESDAY: Sunny, light to moderate southwest wind increasing in the evening, freezing level 1000 m.

THURSDAY: 5-10 cm new snow, strong southwest ridgetop wind, freezing level 1000 m.

FRIDAY: 5-10 cm new snow, moderate westerly ridgetop wind, freezing level valley bottom.

Avalanche Summary

Reporting since the storm has been limited to the Valemount area, which received lowest snowfall in the region. Numerous natural storm slabs up to size size 2 have been observed on a variety of aspects, as well as a machine triggered size 2.5.

Snowpack Summary

Recent snowfall amounts have been in excess of 100 cm in the south of the region near Blue River and north of McBride, and 40-50 cm Barkerville to Valemount. At upper elevations, all of this recent snow has likely been blown around by strong to extreme westerly winds, forming thick, reactive slabs in lee features. At lower elevations, the new snow is likely settling in the mild temperatures.

The recent snow sits on old, facetted and/or extensively wind affected snow that sat on the surface during the extended cold, windy drought period. There is uncertainty around how long it will take for this interface to bond but reports from the Monashees in the neighboring North Columbia region have indicated a positive trend already.

We've now got 80-180 cm of snow above the early February persistent weak layer which is composed of surface hoar. This layer is most prevalent at treeline and in "treeline-like" features like cutblocks. On steep south-facing terrain, this layer may consist of facets on a sun crust. We are awaiting reports of avalanche activity during the storm, specifically whether they indicate step- downs to this layer, to determine whether or not it continues to be a problem.

Terrain and Travel

  • Don't be too cavalier with decision making, storm slabs may remain sensitive to human triggering.
  • Start with simple well supported terrain below treeline and gather information before stepping out.
  • Avoid slopes when the solar radiation is strong, especially if they have large cornices overhead.

Problems

Storm Slabs

An icon showing Storm Slabs

40-100 cm of recent storm sits overtop a thick layer of weak, sugary facets. Due to this weak interface, storm slabs may be surprisingly sensitive to triggering. At upper elevations, the recent snow has likely been blown around by strong to extreme westerly winds, forming thick, reactive slabs in lee features.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Very Likely

Expected Size

1 - 3

Persistent Slabs

An icon showing Persistent Slabs

A persistent weak layer buried 80 to 180 cm deep is being tested by significant new snow loads. We are awaiting reports of avalanche activity during the storm, specifically whether they indicate step- downs to this layer, to determine whether or not it continues to be a problem.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely

Expected Size

2 - 3.5

Valid until: Feb 24th, 2021 4:00PM

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