Purcells Avalanche Forecast

Issued: Jan 3rd, 2021 4:00PM

Mon Jan 4th Current Conditions
Alpine Considerable Treeline Considerable Below Treeline Considerable
Tue Jan 5th 2 Day Outlook
Alpine Considerable Treeline Considerable Below Treeline Moderate
Wed Jan 6th 3 Day Outlook
Alpine Considerable Treeline Moderate Below Treeline Moderate

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is considerable. Known problems include Storm Slabs, Persistent Slabs and Deep Persistent Slabs.

  

25-35 cm of new snow and strong southwesterly winds Saturday night formed widespread reactive storm slabs at all elevations. Human triggering of large storm slab avalanches continues to be likely on Monday.

Summary

Confidence

Moderate - Uncertainty is due to the limited number of field observations.

Weather Forecast

  

SUNDAY NIGHT: Mostly cloudy / Moderate, west ridgetop wind / alpine low temperature -11 / Freezing level valley bottom.

MONDAY: Cloudy with isolated flurries; 0-3 cm. / Strong, southwest ridgetop wind / alpine high temperature -6 / Freezing level 1000 m.

TUESDAY: Mostly cloudy / Moderate, southwest ridgetop wind / alpine high temperature -6 / Freezing level 1000 m.

WEDNESDAY: Cloudy / Strong, southwest ridgetop wind / alpine high temperature -5 / Freezing level 1200 m.

Avalanche Summary

Several natural and skier triggered storm slab avalanches up to size 2 were reported on Saturday.

On Thursday, a ski cut resulted in a size 2 persistent slab avalanche on a northeast aspect in the alpine near Kicking Horse Mountain Resort. MIN report HERE.

A skier triggered avalanche was reported in the Golden area on Wednesday. Check out the MIN report HERE

These recent avalanches are a reminder that when persistent slabs are the problem; conservative terrain choices are the answer.

Snowpack Summary

25-35 cm. of new snow, strong southwest winds and mild temperatures have formed widespread reactive storm slabs at all elevations.

There are currently several layers of concern in much of this region's snowpack. The recent 40-50 cm of snow has buried yet another layer weak layer of surface hoar that was reported in the golden area. The mid December surface hoar is down 90-130 cm. Although there have been no new reports of avalanches on this layer in the last few days, it remains possible to human trigger where it is well preserved. There may also be a crust near or instead of this layer in some areas.

The lower snowpack is characterized by more crusts, the most notable is a rain crust from early November that 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

Storm Slabs

An icon showing Storm Slabs

Likelihood

Likely

Expected Size

1.5 - 2.5

Storm slabs in motion may step down to deeper weak layers, resulting in large avalanches.

Aspects:

All aspects.

Elevations:

All elevations.

Persistent Slabs

An icon showing Persistent Slabs

Likelihood

Possible-Likely

Expected Size

2 - 3

A weak layer of surface hoar down 50-100 cm. has been reactive to human triggers, resulting in large avalanches.

Aspects:

All aspects.

Elevations:

All elevations.

Deep Persistent Slabs

An icon showing Deep Persistent Slabs

Likelihood

Possible

Expected Size

2.5 - 4

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.

Valid until: Jan 4th, 2021 4:00PM