Avalanche Forecast
Issued: Mar 19th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs.
JSmith,
Avalanche Canada
Lingering wind slabs below alpine ridgetops may remain reactive to human triggers. The snowpack is highly variable throughout this region and persistent weak layers may be reactive in isolated areas.
Summary
Confidence
Weather Forecast
FRIDAY NIGHT: Clearing skies / Light, west ridgetop wind / alpine low temperature -25 / Freezing level valley bottom.
SATURDAY: Sunny / Strong, southwest ridgetop wind / alpine high temperature -13 / Freezing level valley bottom.
SUNDAY: Flurries; 3-5 cm. / Light, southwest ridgetop wind / alpine high temperature -12 / Freezing level valley bottom.
MONDAY: Cloudy with isolated flurries; 0-3 cm. / Moderate, west ridgetop wind / alpine high temperature -12 / Freezing valley bottom.
Avalanche Summary
On Thursday, naturally triggered wet loose avalanches to size 1.5 on solar aspects and reactive storm slabs failing on surface hoar near valley bottoms were reported. Additionally, large wind slabs up to size 3 that were 24+ hrs. old were reported in the Tally Ho zone. Thanks for all the great MIN posts, they were super helpful! See MINs HERE.
In some areas, the snowpack is currently more complex and variable than is normal for this region. This means the hard wind slabs may remain reactive to human triggers much longer than is normal in places where they are sitting on a persistent weak layer of facets or surface hoar and will be stubborn to trigger in areas where these layers are not present. See MIN HERE.
Snowpack Summary
Around 30 cm. of recent snow and strong south winds formed wind slabs on lee and cross-loaded features in the alpine. These slabs are sitting on primarily hard surfaces from previous north winds. On solar aspects the recent snow is sitting on a sun crust at treeline and below.
The snowpack inland (between Wheaton and White Pass) has a high degree of variability. A weak layer of buried surface hoar 40-60 cm. down, can be found in isolated sheltered locations. In other locations, a stiff slab sits above weak facets, while others spots are showing a bomber snowpack, suggesting a high degree of spatial variability.
The Wheaton's continental snowpack is dominated by hard wind slabs overlying sugary facets and depth hoar. It's an untrustworthy snowpack structure that requires really good terrain selection and travel habits, or a healthy dose of luck.
Terrain and Travel
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Recent wind has varied in direction so watch for wind slabs on all aspects.
- Avoid lee and cross-loaded terrain.
- Be aware of the potential for large avalanches due to the presence of a persistent slab.
- Avoid exposure to slopes that have cornices overhead.
Problems
Wind Slabs
Recent snow and strong southwest winds continue to from fresh wind slabs on lee and cross-loaded features.
Wind slabs formed from previous north winds may still be reactive to human triggers where they are sitting on persistent weak layers.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Mar 21st, 2021 4:00PM
