Avalanche Forecast
Issued: Mar 22nd, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs.
ahanna,
Avalanche Canada
Watch for fresh storm slabs building throughout the day Tuesday. You may find they get deeper and touchier with elevation. With that in mind, stick to low angle, wind sheltered terrain free from overhead hazard.
Where less than 20 cm falls, alpine danger may be a step lower.
Summary
Confidence
Weather Forecast
Disagreement between weather models have resulted in a high degree of uncertainty in precipitation values. Some areas in the south of the region may receive significantly lower amounts on Tuesday.
Monday: Mainly cloudy with isolated flurries starting. Light northwest winds. Alpine high temperatures around -5.
Tuesday: 20-40 cm of new snow. Strong to extreme south or southwest winds. Alpine high temperatures around -3. Freezing level 1100 m.
Wednesday: 10-20 cm overnight then clearing. Light west winds. Alpine high temperatures around -4. Freezing level 1000 m.
Thursday: Mix of sun and cloud. Northwest wind increasing to strong. Alpine high temperatures around -7. Freezing level 900 m.
Avalanche Summary
MIN reports from Thursday and again on Saturday in the Shames area paint a clear picture of recent slab reactivity in specific wind loaded features. These touchy conditions almost certainly ramped up a few notches on Sunday as heavy snowfall and high winds set up a widespread new storm slab problem.
Natural wind slab releases to size 3 (very large) were observed in the Bear Pass corridor again on Sunday morning, the latest in a string of similar morning observations in this part of the region.
Snowpack Summary
20-40 cm of new snow is forecast to fall through the day Tuesday amid strong southwest wind. The new snow falls on top of 30 cm of recently reactive storm snow sitting on a crust on solar aspects and below 1400 m. At higher elevations where this crust tapers out, the new snow has added significant load to a couple of deeply buried weak layers that we haven't quite ruled out as problems.
The first and most concerning is a roughly 70-100 cm-deep persistent weak layer of surface hoar buried March 12 on sheltered northerly aspects around treeline. Deeper down, around 100 to 300 cm now overlies another layer of surface hoar (and faceted snow) buried in mid-February that may still be a concern in shallower snowpack areas. Although they haven't produced recent avalanches, professionals in the region have been tracking and treating these layers with caution. If it hasn't already been occurring, there is a chance further loading during Tuesday's storm could result in some step-down activity to produce very large and destructive avalanches.
The mid and lower snowpack is well settled and strong in most areas.
Terrain and Travel
- Watch for fresh storm slabs building throughout the day.
- Travel in alpine terrain is not recommended.
- Sheltered low elevation terrain will likely offer the best and safest riding today.
- Choose conservative terrain and watch for clues of instability.
- Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
Problems
Storm Slabs
New snow and strong winds have formed a widespread new storm slab problem that's likely to increase in severity with elevation. Remain cautious if you're noting a generally good bond forming with the old surface, this bond may not be uniform and wind loaded areas are likely primed for human triggered avalanches.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Mar 23rd, 2021 4:00PM
