Avalanche Forecast
Issued: Feb 27th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs, Persistent Slabs and Loose Wet.
swerner,
Avalanche Canada
Warm, wet and windy!
A widespread natural avalanche cycle is likely on Sunday. Its a good time to stay out of avalanche terrain and avoid overhead slopes. Large to very large avalanches could run full path into lower elevations.
Summary
Confidence
Weather Forecast
WET, WARM, and WINDY!
Saturday Night: Snow amounts 15-25 cm. Ridgetop wind strong from the southwest and alpine temperatures near -2. Freezing levels 600 m.
Sunday: Heavy snow 25-40 cm accompanied by strong wind from the southwest. Alpine temperatures near 0 and freezing levels 1000 m.
Monday: Cloudy with light snow 5-10 cm. Ridgetop wind moderate to strong from the southwest. Freezing levels 500 m.
Tuesday: Snow amounts 10-20 cm. Ridgetop wind moderate to strong from the southwest. Alpine temperatures near -3 and freezing levels 600 m.
Avalanche Summary
No new avalanches reported on Saturday.
On Friday, numerous avalanches up to size 3 were triggered with the use of explosives. Many being size 1-2 storm slabs, however; one reported was a size 3 with the suspect failure plane being the mid-February facet interface described in the snowpack summary. A widespread natural avalanche cycle occurred on Thursday and overnight into Friday up to size 3. Additionally, This MIN from earlier this week shows excellent photos of slab avalanches around treeline elevations, potentially releasing on the surface hoar.
I expect a widespread avalanche cycle on Sunday.
It's a good time to stay very conservative, stick to simple terrain, and be aware of overhead hazards like large avalanches and cornices.
Snowpack Summary
Storm after storm, after storm!
30-60 cm of new storm snow fell by Friday morning. This came with strong southwest to northwest wind building fresh wind slabs and storm slabs at upper elevations. Below 800 m mixed precipitation of snow and rain likely fell leaving moist snow surfaces on a snowpack that was recently wet.
This now brings 80-200 cm over the plethora of old snow surfaces buried mid-February and deeper down buried late January. These lold layers comprise of hard wind-packed snow, feathery surface hoar crystals especially in areas sheltered from the wind, sugary faceted snow that developed during the cold snap, and a hard melt-freeze crust below treeline. These weak layers have been the result of several larger avalanches in the past week.
The mid-pack has been reported as being well-settled. There are presently no deeper concerns.
Terrain and Travel
- Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.
- Avoid the runout zones of avalanche paths. Avalanches could run full path.
- Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
- Keep in mind that wet avalanches can be destructive due to their high density.
- Keep in mind that human triggering potential persists as natural avalanching tapers off.
Problems
Storm Slabs
New snow overnight Saturday and Sunday will build reactive storm slabs at upper elevations. The wind is forecast to howl from the northwest to southwest, so wind slabs will rapidly build too. All of this stacks up to another natural avalanche cycle Sunday.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
A persistent slab has recently been reactive to rider and explosive triggering over the past few days. There is anywhere from 80 to 200 cm of snow above a mixed bag of old snow surfaces buried in mid-February. This weak layer will be deeper after Sunday's storm. The primary concern now is storm slab avalanches stepping down to this deep layer and skier or rider triggering which would result in a very-large, consequential avalanche.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Loose Wet
Rising freezing levels to 1000 m and heavy precipitation in the form of rain will likely initiate a loose wet avalanche cycle at treeline and below.
Aspects: All aspects.
Elevations: Treeline, Below Treeline.
Likelihood
Expected Size
Valid until: Feb 28th, 2021 4:00PM
