Avalanche Forecast
Issued: Dec 23rd, 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
The recent storm snow sits on a buried weak layer 100 cm down. This weak layer may be at a tipping point just waiting for a trigger. Conservative terrain selection is crucial until we have good evidence that the layers have stabilized.
Summary
Confidence
Moderate - Uncertainty is due to how quickly the snowpack will recover and gain strength.
Weather Forecast
An upper ridge of high pressure will generally keep the region cool and dry through the forecast period. A weak temperature inversion may slightly warm ridgetop temps on Thursday.
Thursday/Friday: Mix of sun and cloud. Alpine temperatures near -4 and freezing levels valley bottom -6. Ridgetop wind light from the southwest.
Saturday: Light snow 5-10 cm. Alpine temperatures -3 and freezing levels valley bottom. Ridgetop wind moderate from the southwest.
Avalanche Summary
On Wednesday numerous storm slabs up to size 1.5 were triggered with explosives.Â
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.Â
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 remain reactive to human triggers, especially where the wind stiffens the new snow. Deeper slabs will be found on lee slopes due to strong winds.
A persistent slab 80-130 cm thick now sits on the early December crust. This persistent weak layer, with facetted crystals and surface hoar crystals above and/or below it is reaching a tipping point.Â
Deeper in the snowpack are two hard melt-freeze crusts that formed in November that may have some weak crystals around them. This potential avalanche problem is dormant at this time, however; it remains on our radar.
Terrain and Travel
- Storm slabs in motion may step down to deeper layers resulting in large avalanches.
- Shooting cracks, whumphs and recent avalanches are strong indicators of an unstable snowpack.
- Don't let the desire for deep powder pull you into high consequence terrain.
- Good day to make conservative terrain choices.
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. 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, 80-150 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 24th, 2020 4:00PM
