Avalanche Forecast
Issued: Feb 6th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs and Wind Slabs.
kdevine,
Avalanche Canada
Persistent slab avalanches may still be easy to trigger. Continue to choose conservative terrain.
A change in wind direction means that wind loading may exist on all aspects, pay close attention to changing conditions as you enter wind exposed terrain.
Summary
Confidence
Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.
Weather Forecast
SATURDAY NIGHT - Mainly cloudy with a few flurries, 3-5 cm / moderate northwest wind / alpine low temperature near -20Â
SUNDAY - Cloudy with sunny periods and isolated flurries / moderate to strong northwest wind / alpine high temperature near -16
MONDAY - Cloudy with sunny periods and isolated flurries / light to moderate north wind / alpine high temperature near -18
TUESDAY - A mix of sun and cloud / light northwest wind / alpine high temperature near -17
Avalanche Summary
As natural avalanche activity tapers, wind slabs and persistent slabs may still be primed for triggering. These may propagate widely and can catch you by surprise even in low angle terrain. Moderate northerly winds are likely building fresh and reactive wind slabs which may be easy to trigger.
On Friday, there were numerous reports of natural and human triggered persistent slab avalanches up to size 2.5. Some of these were triggered remotely, as outlined in a MIN report that can be viewed here. There were also numerous natural and explosives triggered dry loose, and storm slab avalanches reported up to size 2.Â
It has been a busy week for avalanche activity, with reports of natural, human, and explosives triggered storm and/or persistent slab avalanches up to size 2 every day for the past week. On Wednesday, persistent slab avalanche activity really picked up and has been a daily occurrence ever since.
Many thanks for all of the great MIN reports over the past week!
Snowpack Summary
Up to 80 cm of recent snow has formed a reactive slab on top of a persistent weak layer that consists of surface hoar, facets, and a crust that was buried in late January. This slab of recent snow sits on top of a plethora of old snow surfaces: hard wind slab, wind-scoured areas, sastrugi, and isolated pockets of soft snow. Below 1800 m a hard melt-freeze crust is underneath the new snow. Â
A solid mid-pack sits above a deeply buried crust and facet layers near the bottom of the snowpack (150-200 cm deep), which is currently unreactive.Â
Terrain and Travel
- Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
- Use conservative route selection. Choose simple, low-angle, well-supported terrain with no overhead hazard.
- Be aware of highly variable recent wind loading patterns.
- Look for signs of instability: whumphing, hollow sounds, shooting cracks, and recent avalanches.
- Pay attention to cornices and give them a wide berth when traveling on or below ridges.
Problems
Persistent Slabs
50-80 cm sits above a buried weak layer of surface hoar, facets, and a crust. These slabs have been very reactive to human triggers, showing wide propagations in moderate to low angle terrain. These avalanches have been catching people by surprise.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Wind Slabs
20-40 cm of new storm snow has slowly accumulated over the past few days. Changing wind directions will likely form reactive slabs on multiple aspects. Avalanches will be most likely in wind loaded areas and where the snow feels stiff or slabby.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Feb 7th, 2021 4:00PM
