Avalanche Forecast
Issued: Feb 28th, 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.
swerner,
Avalanche Canada
Don't let the break in between storms lure you into complex terrain. Stick to simple terrain and avoid overhead avalanche paths. Large storm and persistent slab avalanches will be reactive on Monday.
Summary
Confidence
Weather Forecast
A short break in systems Monday will see the precipitation ease. A zonal flow Tuesday will bring snow and strong west-southwest wind to the region through the forecast period.
Monday: Snow amounts 5-10 cm. Ridgetop wind 20-60 km/hr from the southwest. Alpine temperatures near -5 and freezing levels 500 m.
Tuesday: Snow 15-20 cm. Ridgetop wind 20-70 km/hr from the southwest. Alpine temperatures near -3 and freezing levels 600 m.
Wednesday: Snow 20-30 cm. Ridgetop wind generally light from the southwest. Alpine temperatures -3 and freezing levels 700 m.
Avalanche Summary
On Sunday, a widespread natural avalanche cycle occurred up to size 2.5 and explosive control initiated numerous size 2-3 storm slabs.
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.
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
15-35 cm of new snow fell by Sunday morning adding to the 30-60 cm of new storm snow that fell Friday. This came with moderate to strong west-northwest wind building fresh wind slabs and storm slabs at upper elevations. Below 1000 m mixed precipitation of snow and rain likely fell leaving moist snow surfaces on a snowpack that was recently wet.
This now brings 90-250 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 the runout zones of avalanche paths. Avalanches could run full path.
- Storm slabs in motion may step down to deeper layers resulting in large avalanches.
- Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
- Stick to non-avalanche terrain or small features with limited consequence.
Problems
Storm Slabs
Up to 30 cm of new storm snow fell at upper elevations Sunday. Storm slabs are reactive at upper elevations, potentially running full path into lower elevations. The wind is forecast to howl from the southwest, so wind slabs will rapidly build too.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
The persistent slab has recently been reactive to rider and explosive triggering over the past few days. There is anywhere from 90 to 250 cm of snow above a mixed bag of old snow surfaces buried in mid-February. 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
Valid until: Mar 1st, 2021 4:00PM
