Avalanche Forecast
Issued: Dec 23rd, 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.
wlewis,
Avalanche Canada
Give the snowpack time to strengthen before pushing into bigger terrain. Expect deeper and more reactive deposits in wind loaded features as you move to higher elevations. Sheltered slopes with minimal wind effect will offer the best conditions.
Summary
Confidence
Weather Forecast
The trough exits the region, leaving flurries in its wake. Arctic air begins to push South into the interior, steadily dropping temperatures. Expect a daily refresh of low density snow through to Boxing Day.
THURSDAY NIGHT: Light snowfall brings up to 5cm overnight with moderate southwest winds.
FRIDAY: Cloudy skies with flurries over the day, up to 5cm. Winds remain moderate from the southwest. Alpine high of -10.
SATURDAY: Cloudy with light snowfall, 2-5cm over the day and another 5-10cm overnight. Moderate to strong southerly winds. Alpine high of -8.
SUNDAY: Light snowfall with moderate easterly winds. Alpine highs of -15.
Avalanche Summary
Naturally triggered slab avalanches to size 1.5 were observed on all aspects yesterday at treeline and above with the addition of heavy snowfall and wind. Several human triggered slabs up to 40cm deep were also reported.
Explosive control near Revelstoke produced slab avalanches to size 2 in wind loaded features in treeline and alpine elevations.
If you go out in the mountains, please submit your findings and photos through a Mountain Information Network report.
Snowpack Summary
Up to 30cm of new snow has fallen this week. Recent strong southwest winds have created deeper slabs in wind loaded features at treeline and above.
Prior to this storm, a weak layer of surface hoar formed. These grains are expected to have been preserved on sheltered slopes at treeline and below. Expect increased reactivity of the storm snow in these areas.
The most significant feature in the snowpack is a widespread thick crust that formed in early December. It sits 70-150cm deep in the snowpack and exists up to 2400m. In some places, overlying snow is well-bonded to the crust, but in others, weak faceted grains have been observed above it. The facets above the crust are most prominent at treeline where the crust is thinner. In areas where the crust is buried deeper than one meter, it starts to decompose and show variable reactivity.
Terrain and Travel
- Continue to make conservative terrain choices while the storm snow settles and stabilizes.
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Avoid rock outcroppings, convexities, and anywhere the snowpack is thin and/or variable.
Problems
Storm Slabs
Storm slabs will remain reactive to a riders weight as they begin to gain strength. Take care when moving through wind affected terrain and higher elevations - storm snow has been redistributed by southwest winds into deeper slabs in wind loaded features. Expect slabs to keep building as winds continue to transport snow into lee sheltered features.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
A layer of weak facets (sugary snow) can be found down 70-150 cm near a thick crust layer that formed in early December. Although this persistent weak layer hasn't recently shown reactivity in this area, it is possible to trigger avalanches on this layer, especially at treeline elevations.
The best strategy with a persistent avalanche problem is conservative terrain management - avoid likely trigger spots such as steep convex slopes, and areas where the snowpack tapers rapidly from thick to thin.
Aspects: All aspects.
Elevations: Treeline, Below Treeline.
Likelihood
Expected Size
Valid until: Dec 24th, 2021 4:00PM
