Avalanche Forecast
Issued: Dec 26th, 2022 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Persistent Slabs.
jpercival,
Avalanche Canada
Temperatures and freezing levels are rising, expect that reactivity of both the wind slab and persistent weak layer avalanche problems to increase.
Recent snow and strong winds have built wind slabs at all elevations.
Summary
Confidence
Moderate
Avalanche Summary
On Sunday reports of numerous explosive control avalanches have been submitted. Between the elevations of 2000 and 2300 m, these avalanches were mostly located on north through to east aspects, large (size 2) and within the new storm snow. Crown depths were consistent at 40 plus centimeters deep, running generally 200 meters with one running 400 meters.
One natural avalanche was reported as Very large (size 2.5) 40cm deep and running approx. 250 meters
On Thursday loose dry avalanches to size 2 were reported in steep terrain features.
A natural size 2.5 persistent slab avalanche was reported, thought to have occurred on Tuesday. This avalanche occurred on a northeast aspect, 2000 m on a reloaded bed surface.
Snowpack Summary
On Saturday 15 to 20 cm of new snow was redistributed by strong southerly winds. Larger deposits in east and north facing terrain can now be found and has formed new wind slabs. Slabs have formed over facets, surface hoar or a crust and they may not bond well.
Around 50 cm deep a layer of surface hoar at treeline and a thin crust on steep south facing slopes exists buried in early December.
The primary concern in the snowpack is the mid-November layer consisting of facets and surface hoar, buried around 80 cm deep. This layer is likely to become reactive as temperatures increase on Tuesday.
The lower snowpack presents as primarily facetted combined with depth hoar. Ice has been reported to exist at the base in a few different locations.
The snowpack in the forecast region is quite variable with snowpack depths at treeline varying from 100 cm to 200 cm.
Weather Summary
Monday Night
Cloudy with light snowfall 5 to 10 cm. Strong southwesterly winds 100 to 60 km/h . Freezing levels 500 m with an above freezing layer from 1300 to 2000 m . High temperatures of 0°C.
Tuesday
Cloudy with 5-15 cm of mixed precipitation expected. Strong southwest winds becoming moderate mid day 60- 40 km/h. Freezing levels 1000 m with an above freezing layer from 1300 to nearly 2500. High temperatures of +2°C.
Wednesday
Cloudy with light snow 1 to 5 cm. Light southwesterly wind. Freezing levels and temperatures begin to descend with alpine temperatures dropping to -6°C.
Thursday
Cloudy with light snow 1 to 5 cm. Light southwesterly wind. Freezing levels at valley bottom, alpine temperatures dropping to -9°C.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Storm slab size and sensitivity to triggering will likely increase through the day.
- Watch for fresh storm slabs building throughout the day.
- Storm slabs in motion may step down to deeper layers resulting in large avalanches.
Problems
Wind Slabs
Fresh snow and strong winds has built new and reactive slabs. Expect winds to redistribute snow at treeline and alpine elevations into deeper and more reactive slabs in wind loaded features. Where strong winds are observed slabs could be found further down slope than expected.
Expect slabs to become very reactive as the temperatures and freezing levels rise.
Expect slabs to be reactive as they sit over a variety of weak surfaces - facets, a crust and/or surface hoar.
Aspects: North, North East, East, South East, South, North West.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
Two concerning persistent weak layers can be found in the snowpack. The first is a surface hoar/crust layer from early December and the second is a surface hoar, facet or crust layer from mid November. These layers are most concerning on sheltered treeline features where surface hoar is most likely to be preserved.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Dec 27th, 2022 4:00PM
