Avalanche Forecast
Issued: Feb 25th, 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.
kdevine,
Avalanche Canada
The snowpack is currently complex and there have been some large human-triggered avalanches recently. It is important to continue to choose conservative terrain as signs of instability may not be obvious.
Summary
Confidence
Weather Forecast
THURSDAY NIGHT - Flurries, 5-10 cm / moderate to strong southwest wind / alpine low temperature near -12
FRIDAY - Mainy cloudy with flurries, 5 cm / moderate northwest wind / alpine high temperature near -11
SATURDAY - A mix of sun and cloud with a few flurries / moderate west wind / alpine high temperature near -11
SUNDAY - Mainly cloudy with scattered flurries, 5 cm / strong southwest wind / alpine high temperature near -6 / freezing level 1600 m
Avalanche Summary
Observations from McBride and Valemount areas show evidence of a widespread natural avalanche cycle that took place during the recent storm.
Several natural and human-triggered avalanches size 2-3.5 were reported on Tuesday near Valemount at alpine and treeline elevations. At least one of the very large human-triggered avalanches was initiated from a wind-loaded start zone at the top of a large alpine feature, propagated for hundreds of meters along a ridge, and ran to valley bottom. Thankfully the rider was able to escape unharmed.
On Tuesday, there was a fatal avalanche just outside of the region, northeast of Valemount in Swift Creek. The avalanche was a size 3.5 and is suspected to have failed on the late January persistent weak layer. The report can be found here.
Snowpack Summary
The region has received 40-80 cm of fresh snow in recent days. There are wind deposits up to 100 cm deep in lee features at upper elevations. The recent snow sits on faceted, and/or previously wind-affected snow that formed on the surface during the extended cold, dry period.
There is now 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 such as cutblocks. On steep south-facing terrain, this layer may consist of facets on a sun crust.
A persistent weak layer from late January exists down 90-200 cm. There have been very few recent reports of avalanches or reactive test results on this layer, however, there have been several large avalanches on this layer in the neighboring North Rockies region in recent days, so it is worth keeping in mind.
Terrain and Travel
- Fresh snow rests on a problematic persistent slab, don't let good riding lure you into complacency.
- Be aware of the potential for large avalanches due to the presence of a persistent slab.
- Uncertainty is best managed through conservative terrain choices at this time.
- Be especially cautious as you transition into wind affected terrain.
Problems
Storm Slabs
Fresh snow combined with moderate to strong winds will likely continue to form fresh and reactive storm slabs, especially in wind-loaded areas. A change in wind direction on Friday may mean wind loading can be found on all aspects.
Cornices are experiencing rapid growth with strong west to southwest winds, use caution on ridgelines, and in terrain with cornices above.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
40-80 cm of recent storm snow sits on a layer of weak, sugary facets. At upper elevations, the recent snow has been blown into reactive slabs in lee features. Recent avalanches have propagated widely and surprised riders.
Two more persistent weak layers are buried between 80-200 cm. These have not produced recent avalanches in the region that we know of, but have been responsible for several recent large avalanches in the neighboring North Rockies region, including two fatal avalanches in the past week.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Feb 26th, 2021 4:00PM
