Avalanche Forecast
Issued: Feb 21st, 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.
mconlan,
Avalanche Canada
A storm will impact the region Sunday night into Monday, forming new slabs, destabilizing the snowpack, and increasing the likelihood of triggering buried weak layers. An avalanche cycle may occur at all elevation bands. Travel in avalanche terrain is not recommended.
Summary
Confidence
Moderate - Uncertainty is due to the track & intensity of the incoming weather system.
Weather Forecast
SUNDAY NIGHT: Cloudy with snowfall, accumulation 10 to 20 cm with locally more snowfall possible, 50 gusting to 100 km/h southwest wind, alpine temperature -5 C, freezing level 1300 m.
MONDAY: Cloudy with snowfall, accumulation 5 to 15 cm, 40 to 80 km/h southwest wind, alpine temperature -5 C, freezing level 1600 m.
TUESDAY: Cloudy with snowfall, accumulation 5 to 10 cm, 30 to 40 km/h west wind, alpine temperature -8 C.
WEDNESDAY: Clear skies, 20 km/h southwest wind, alpine temperature -9 C.
Avalanche Summary
Many human-triggered avalanches have been triggered on the buried weak layer described in the snowpack summary. Check here for the most recent event and otherwise scroll through the loads of MINs on the map or list view. In general, the avalanches were small to large (size 1-2), around 40 to 70 cm thick, most commonly occurring at treeline elevation but also below treeline in open trees, and they have released on surprisingly low angle terrain.
Looking towards Monday, an avalanche cycle may occur if the forecasted precipitation occurs, with storm, wind, and persistent slabs at treeline and alpine elevations and loose wet avalanches below treeline. It will be a good day to avoid avalanche terrain!
Snowpack Summary
Somewhere around 20 to 50 cm of snow is forecast to accumulate by Monday afternoon. The freezing level is forecast to be up to 1600 m so rain will soak the snowpack below and storm slabs are expected to rapidly build above. The wind is forecast to be strong to extreme, meaning wind slabs will also form in exposed terrain. This is all a recipe for an avalanche cycle!
The snow and rain will load a weak layer found around 50 to 100 cm deep. The layer may consist of weak and feathery surface hoar, sugary faceted grains, or faceted grains associated with a hard melt-freeze crust. Many avalanches in the past few weeks have been triggered on these layers.
There are presently no deeper concerns.
Terrain and Travel
- Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.
- Travel in alpine terrain is not recommended.
- The trees are not the safe-haven they normally are at this time. Terrain at treeline is primed for human triggered avalanches.
Problems
Storm Slabs
Forecasted snow and strong wind will rapidly form new storm and wind slabs. Weather models suggest 20 to 40 cm of snow by Monday late afternoon but enhanced snowfall may occur, bringing even more to the region. Best to avoid avalanche terrain if you find 25+ cm of snow accumulation, as an avalanche cycle may occur.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
Loads of large avalanches have been triggered on this layer of surface hoar, faceted grains, and/or a melt-freeze crust, now found around 50 to 100 cm deep. The layer has been most problematic around treeline elevations and in openings below treeline, but also reaches into the lower alpine. Avalanches have occurred on surprisingly shallow slope angles and they can easily be remotely triggered.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Loose Wet
Rain below the snow-rain line will rapidly destabilize the snowpack and promote wet loose avalanche activity.
Aspects: All aspects.
Elevations: Below Treeline.
Likelihood
Expected Size
Valid until: Feb 22nd, 2021 4:00PM
