Avalanche Forecast
Issued: Dec 26th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs, Persistent Slabs and Deep Persistent Slabs.
JSmith,
Avalanche Canada
Buried weak layers in the middle and bottom of the snowpack continue to be a significant concern. Conservative terrain choices are key to avoiding these large and destructive avalanches.
Summary
Confidence
Weather Forecast
SATURDAY NIGHT: Cloudy with flurries; 0-3 cm. / Moderate to strong, northwest ridgetop wind / alpine low temperature -12 / Freezing level valley bottom.
SUNDAY: Mostly cloudy with sunny periods. / Light, northwest ridgetop wind / alpine high temperature -8 / Freezing level valley bottom.
MONDAY: Cloudy / Light, northwest ridgetop wind / alpine high temperature -9 / Freezing level valley bottom.
TUESDAY: Mix of sun and cloud / Light, northwest ridgetop wind / alpine high temperature -10 / Freezing level valley bottom.
Avalanche Summary
On Wednesday there was a report of a snowmobile triggered size 2 deep persistent slab avalanche in the north of the region. This MIN post highlights the avalanche and the current nature of the snowpack.
On Tuesday there were several reports of deep persistent slab avalanches running size 2-3 on southeast, east and northeast aspects. Three of these were size 2's triggered by skiers. Check out this MIN report from Tuesday afternoon for an example.
Snowpack Summary
30 to 75 cm. of storm snow fell last weekend and into Monday. Winds blowing from a variety of directions formed slabs in lee features at upper elevations, reactive cornices have grown too.
Below the storm snow, there are several critical layers of concern. The early December surface hoar is down 30 to 80 cm. It has recently been sensitive to remote triggering which is well illustrated in this MIN post from the Golden area.
Below, or near the surface hoar you may encounter a crust. This crust has been observed as high as 2400 m. in the south of the region and 1800 m. in the north.
The lower snowpack is characterized by more crusts, the most notable is a rain crust from early November that is 50 to 130 cm deep. This crust is sitting near the base of the snowpack, surrounded by a weak layer of sugary facets. It is most likely to be reactive to human triggers in steep, shallow, rocky areas with a thin to thick snowpack.
Terrain and Travel
- Uncertainty is best managed through conservative terrain choices at this time.
- If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
- Be aware of the potential for large avalanches due to the presence of buried persistent weak layers.
- Remote triggering is a concern, watch out for adjacent and overhead slopes.
- Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
Problems
Wind Slabs
Wind switching directions has created wind slabs on a variety of aspects.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
A weak layer of surface hoar down 40-90 cm. has been reactive to human triggers, resulting in large avalanches.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Deep Persistent Slabs
A Crust buried near the bottom of the snowpack has been responsible for some very large explosive triggered avalanches up to size 4.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Dec 27th, 2020 4:00PM
