Avalanche Forecast
Issued: Jan 12th, 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
Widespread natural avalanche activity is expected. Avoid avalanche terrain, including overheard hazard.
Summary
Confidence
Weather Forecast
TUESDAY NIGHT - Snow, 20-30 cm / southwest wind, 40-80 km/h / alpine low temperature near -2 / freezing level 2000 m
WEDNESDAY - Flurries, 10-15 cm / west wind, 60-80 km/h / alpine high temperature near -1 / freezing level 1500 m
THURSDAY - Mainly sunny / light northwest wind / alpine high temperature near -8
FRIDAY - A mix of sun and cloud / light to moderate west wind / alpine high temperature near -7
Avalanche Summary
A natural avalanche cycle is expected on Wednesday. This may include very large persistent slab avalanches.
On Sunday, there were a few explosives triggered persistent slab avalanches to size 2.5. These were reported to have failed on weak facets above a crust that was buried in early December.
On Saturday, explosive testing near Fernie produced several large persistent slab avalanches up to size 2.5 also failing on the early December persistent weak layer.
A couple of large (size 3) naturally triggered persistent slab avalanches were reported on large alpine features on Thursday. These avalanches were triggered by either smaller wind slab avalanches, or cornice falls. These are continued reminders of the "low probability; high consequence" scenario that persistent slab problems often create.
Snowpack Summary
Tuesday brought upwards of 30 cm of new snow to the region, and another 30-45 cm with strong to extreme southwest wind is expected between Tuesday night and Wednesday afternoon. Storm slabs are anticipated to be widespread and reactive.
Roughly 50-80 cm of snow is now sitting on a crust that extends up to 1900 m. In isolated areas below treeline, this recent snow may be sitting on a weak layer of surface hoar.
The main feature we are monitoring in the snowpack is a layer of weak faceted snow over a hard melt-freeze crust found around 90-150 cm down. Recent sporadic, large, naturally triggered avalanches have occurred on this layer on large alpine slopes and were triggered by either smaller wind slab avalanches, or cornice falls.
Terrain and Travel
- Avoid all avalanche terrain during periods of heavy loading from new snow and wind.
- Avoid exposure to overhead avalanche terrain, avalanches may run surprisingly far.
- Storm slabs in motion may step down to deeper layers resulting in large avalanches.
Problems
Storm Slabs
Lots of new snow has fallen in the region with strong to extreme winds. Natural avalanches are expected.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
This storm is adding a big load to a deeply buried weak layer. Avalanches triggered on this layer will be large and destructive.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Jan 13th, 2021 4:00PM
