Avalanche Forecast
Issued: Feb 22nd, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Persistent Slabs.
ahanna,
Avalanche Canada
As we head into a couple days of friendlier weather, resist the allure of bigger terrain and be especially wary of recently wind loaded features. Recent storm snow sits on a thick layer of weak, sugary facets and bonding at this interface may take some time.
Summary
Confidence
Moderate - Uncertainty is due to how quickly the snowpack will recover and gain strength.
Weather Forecast
MONDAY NIGHT: Around 5 cm of new snow, moderate to strong northwest wind, freezing level valley bottom.
TUESDAY: Scattered flurries with sunny periods, light northwest wind, freezing level 800 m.
WEDNESDAY: Sunny, light to moderate southwest wind, freezing level 800 m.
THURSDAY: 5-10 cm new snow, moderate to strong southwest wind, freezing level 1000 m.
Avalanche Summary
Avalanche observations have been limited due to poor visibility in the storm.
Last week, older winds slabs in cross and reverse-loaded terrain features surprised a number of skiers, triggering avalanches up to size 2.5. This surprisingly large human triggered avalanche was reported on a northwest facing feature at treeline.
Snowpack Summary
Recent snowfall amounts have been in excess of 100 cm in the south of the region near Blue River, around 80 cm north of McBride, 40 cm in the east near Barkerville and 30 cm near 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 and gaining slab property 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.
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
- Fresh snow rests on a problematic persistent slab, don't let good riding lure you into complacency.
- Stay off recently wind loaded slopes until they have had a chance to stabilize.
- Brief periods of sun could quickly initiate natural avalanche activity.
- Storm slabs in motion may step down to deeper layers resulting in large avalanches.
Problems
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
Expected Size
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
Expected Size
Valid until: Feb 23rd, 2021 4:00PM
