Avalanche Forecast
Issued: Dec 22nd, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Persistent Slabs.
swerner,
Avalanche Canada
A widespread avalanche cycle occurred in response to the recent storm. Large storm slabs remain primed for human triggering on Wednesday. Conservative terrain selection is crucial as the snowpack slowly settles and stabilizes.
Summary
Confidence
Weather Forecast
A high-pressure system off the coast will bring generally cooler, more seasonal-like temperatures and clearing to the region.
Wednesday/ Thursday: Mainly sunny and alpine temperatures near -7. Ridgetop wind 25km/hr from the West. Slight alpine temperature inversion. Freezing levels valley bottom.
Friday: Cloudy with sunny periods. Alpine temperatures near -5 and freezing levels 1000 m. Ridgetop wind light from the southwest.
Avalanche Summary
On Tuesday, a widespread natural avalanche cycle up to size 3 was reported from the lizard range. Natural avalanche activity may taper off a bit but the snowpack remains primed for human triggering.
Please consider sharing your observations on the Mountain Information Network. Thank you to those that have already submitted this winter!
Snowpack Summary
30-50 cm of recent storm snow blanketed the region by Tuesday morning. Storm slabs will likely be reactive, especially where the wind stiffens the new snow. Deeper slabs will be found on lee slopes.
A persistent slab 80-130 cm thick now sits on the early December crust. There is increasing evidence that this persistent weak layer, with facetted crystals and surface hoar crystals above and/or below it is reaching a tipping point.
Deeper in the snowpack are two hard melt-freeze crusts that formed in November that may have some weak crystals around them. There is uncertainty if and where in the region this may be a problem.
Terrain and Travel
- Storm slabs in motion may step down to deeper layers resulting in large avalanches.
- Good day to make conservative terrain choices.
- Don't let the desire for deep powder pull you into high consequence terrain.
- Shooting cracks, whumphs and recent avalanches are strong indicators of an unstable snowpack.
Problems
Storm Slabs
Storm slabs will likely be reactive and require patience and time to settle and stabilize. These may be extra touchy on lee slopes where wind loading has built deeper slabs. Simple, low angle terrain away from overhead hazard is a good choice right now.
Loose-dry sluffing from steep terrain is likely, especilly when the sun comes out.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
This layer has reached a tipping point. Depending on elevation and aspect, 40-100 cm of snow currently sits above a buried crust from early December. Sugary, facets and surface hoar around the crust mean persistent slabs are likely reactive, especially to human triggers.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Dec 23rd, 2020 4:00PM
