Avalanche Forecast
Issued: Dec 25th, 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 will increase.
Recent snow and strong winds have built wind slabs at all elevations.
Summary
Confidence
Moderate
Avalanche Summary
On Thursday loose dry avalanches to size 2 were reported in steep terrain features.
On Tuesday explosive control produced a few small avalanches, up to size one.
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 had been redistributed by strong southerly winds. Larger deposits in east and north facing terrain can now be found and have 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 Monday and Tuesday.
The snowpack in the forecast region is quite variable with snowpack depths at treeline varying from 100 cm to 200 cm.
Weather Summary
Sunday Night
Mostly cloudy with light flurries bringing trace amounts of new snow. Moderate westerly winds. Freezing levels around 500 m, high temperatures of -7°C.
Monday
Cloudy with 15-20 cm of mixed precipitation expected. Strong southwest winds will thought the day. Freezing levels rising, to around 1000 m with an above freezing layer likely from 1300 to nearly 2500 m in the south. High temperatures of +2°C.
Tuesday
Wet snow and rain continues overnight with another 20 to 25 mm forecast, while freezing levels rise to around 1800 m over the day.
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.
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 26th, 2022 4:00PM
