Avalanche Forecast
Issued: Dec 28th, 2022 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Persistent Slabs.
lbaker,
Avalanche Canada
Conditions are slowly improving as freezing levels drop but be mindful that deep instabilities are still present at higher elevations. If triggered storm slabs may step down to deeper layers resulting in large, destructive avalanches.
Summary
Confidence
Avalanche Summary
On Tuesday, Explosives control produced numerous storm slab avalanches to size 2.5. They also had several persistent slab avalanche results, up to size 3. This is evidence that the persistent weak layer is still with us and will result in large destructive avalanches with the right trigger.
On Monday, evidence of a natural avalanche cycle, both wet slab, and wet loose avalanches were observed on all aspects at all elevations. Avalanches were up to size 3 and likely occurred during the rain event Sunday night.
Please continue to post your observations and photos to the Mountain Information Network.
Snowpack Summary
20-40 cm of dry storm snow sits above a rain crust found at alpine and treeline. 30-40 cm of wet snow is found beneath the crust. Extreme southerly winds have pressed surfaces and redistributed snow into thick slabs in alpine lees. The new snow covered a layer of weak and unconsolidated snow produced by the recent cold weather.
A number of layers persist deeper in the snowpack, consisting of facets, surface hoar, and crusts. On Tuesday explosives control triggered numerous avalanches on these layers
Below treeline, a saturated snowpack is refreezing into firm surfaces. Total snow depths are roughly 90-140 cm at treeline and up to 200 cm in the alpine.
Weather Summary
Wednesday Night
Isolated flurries, trace accumulation. Southwesterly winds 20-30 km/h. Ridgetop low temperature -8 C. Freezing levels 500-700 m.
Thursday
Periods of snow, 5-15 mm. Southerly winds 20 km/h gusting to 40 km/h. Ridgetop high temperature -4 C. Freezing levels rise from 500m to 900 m by the end of the day.
Thursday night, light flurries continue bringing an additional 5 mm and 900 m freezing levels.
FridayCloudy with flurries, 10-15 mm. Southerly winds 40 km/h. Ridgetop high temperature -5 C. Freezing levels hover from 800 m to 1100 m.
SaturdayCloudy with isolated flurries, 2-5 mm. Light to moderate southwesterly winds. Ridgetop high temperature -5 C. Freezing levels hover near 1000 m.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- In times of uncertainty conservative terrain choices are our best defense.
- Continue to make conservative terrain choices while the storm snow settles and stabilizes.
- Be alert to conditions that change with aspect and elevation.
Problems
Storm Slabs
20-40 cm of dry storm snow sits above a rain crust found at alpine and treeline. 30-40 cm of wet storm snow is found beneath the crust. Be especially cautious transitioning into wind-loaded terrain, where storm slabs are deep and may be reactive to human-triggering.
If triggered storm slabs may step down to deeper layers resulting in very large avalanches.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
A crust with weak, facetted snow above and below is buried by roughly 50-150 cm of snow. On Tuesday explosives control triggered numerous avalanches on this layer. Above 2000 m avalanches broke under the crust and stepped down to deeper layers resulting in large avalanches.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 29th, 2022 4:00PM
