Avalanche Forecast
Issued: Dec 22nd, 2020 4:19PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs, Deep Persistent Slabs and Loose Dry.
Stephen Holeczi,
Avalanche control Mt Whymper, Vermillion Peak and Mt. Simpson Wednesday. No activities in these areas. Its a complex snowpack which varies across the region. Give the new load some time to adjust.
Summary
Weather Forecast
No new snow is expected over the next few days. On Wednesday NW winds will pick up in the afternoon into the strong range at 3000m. Temperatures will drop to -15C or lower in some areas Wed. AM, and alpine temperatures slightly warmer.
Snowpack Summary
An upslope storm dropped up to 35cm in Banff and Sunshine, and less (7-10cm) North and West. This was on top of 30-60cm over the last week. The Dec 13 and Dec 7 sun crust/surface hoar/facet layers are down ~ 50cm and ~80 cm respectively. The decomposing Nov crust/facets sits at the bottom of the snowpack. Height of snow at tree line is 80-150cm.
Avalanche Summary
Avalanche control Tuesday at Sunshine and Yoho regions produced slides up to size 3. Many were starting as slabs and propagating other slabs at treeline. One avalanche stepped down 2m to the basal facets/crust. A report of a remote triggered 2.5 deep persistent slab near the Watermelon Peak area from today.
Confidence
Problems
Storm Slabs
Upslope snow dumped 30+cm in the East, and less North and West(10cm).This problem encompasses avalanches within this past weeks storm snow (~40-60cm), and ones sliding on the Dec 7 or 13th layers.These slabs seemed most reactive at treeline. Tuesday.
- If triggered the storm slabs may step down to deeper layers resulting in large avalanches.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Deep Persistent Slabs
We have had a few observations of avalanches stepping down to the Nov. 5 crust and facets. This is a problem with higher uncertainty, and is most prevalent in shallow snowpack areas where the layer has weakened over time.
- Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.
- Avoid avalanche terrain.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Loose Dry
This will be more of a problem in upslope regions as it received the most snow in the last 24 hours. Increased alpine winds will keep this problem active in the short term.
- Minimize overhead exposure during periods of heavy loading from new snow, wind.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Dec 23rd, 2020 4:00PM
