Avalanche Forecast
Issued: Dec 20th, 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.
jcoulter,
Avalanche Canada
A new storm with intense loading rates is set to hit the region by Monday afternoon and continue overnight. Danger ratings may rise to HIGH by late afternoon. Avoid all avalanche terrain during periods of heavy loading from new snow and wind.
Summary
Confidence
Weather Forecast
SUNDAY NIGHT - Early evening flurries, minor accumulations / light to moderate south west wind / low -4
MONDAY DAY - Moderate to heavy accumulations 15-25 cm / moderate south west wind / high of -1
MONDAY NIGHT - 20-30 cm / gusty south west winds / low of -4
TUESDAY - Cloudy with lingering flurries, light accumulations possible / windy at times / high of -3
WEDNESDAY- Sunny with cloudy periods, high of -5
Avalanche Summary
On Sunday there was extensive natural and explosives triggered avalanche activity up to size 3.
There have also been a few accidentally skier triggered avalanches involving both storm snow and the December crust layer such as this one from the MIN.
On Saturday explosives produced results up to size 2 on the early December crust. On Friday there were a few natural size 2 wind slab avalanches reported in the alpine.
Please consider sharing your observations on the Mountain Information Network. Thank you to those that have already submitted this winter!
Snowpack Summary
After a break Sunday night, snow will pick up again on Monday. This continued loading will mean more new reactive storm slabs.
Depending on aspect and elevation 60-100 cm 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 are 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
- Avoid all avalanche terrain during periods of heavy loading from new snow and wind.
- Don't let the desire for deep powder pull you into high consequence terrain.
- Storm slabs in motion may step down to deeper layers resulting in large avalanches.
Problems
Storm Slabs
The snowpack isn't getting much time to adjust to recent snowfall and wind as a new wave of precipitation is set to hit the region Monday afternoon. Simple, low angle terrain away from overhead hazard is a good choice right now.
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 21st, 2020 4:00PM
