It's been quite a week for weather in western Canada. Mountain conditions rapidly jumped from mid-autumn to full-on winter in a matter of days, and we've witnessed a natural disaster of an unprecedented scale with the destruction of transportation lines in southern BC.
Early in the week (Sunday/Monday) the new snow levels resulted in high avalanche hazard (Level 4) and a widespread natural avalanche cycle to Size 3, which is unusual for this time of the year. Avalanche hazard has quickly dropped to Considerable and Moderate (3 and 2) depending on the forecast zone. A small storm rolling in this weekend will elevate the hazard again with light snowfall amounts in the forecast, accompanied by strong to extreme winds that will create new windslab problems.
There's a temperature/rain crust being reported up to 1900 m (Rogers Pass) and 2100 m (Rockies) -- approximately treeline eleavations -- that resulted from the warm temps during the storm. Snow amounts are consequently quite a bit less at lower elevations than in the alpine where this crust disappears. This crust is buried by at least a dusting and up to 20 cm depending on the area.
On the west side of the Rockies new snow amounts vary from 65 (Rockies west slopes) to 120 cm (Rogers Pass) and even more elsewhere. This recent storm snow sits on top of previous snow (10-30 cm) overlying the early November and October crusts and facets. On the east side of the Rockies there was quite a bit less -- around 30 cm overlying the early season crusts.
The National Parks have started issuing full bulletins including hazard ratings, avalanche problems, and snowpack description details. Avalanche Canada will provide forecasts for their forecast zones starting Thursday, November 25.
Avalanche -- our long summer/fall is over; it's time to switch our thinking to winter. All mountain travelers should head out fully equipped with solid avalanche training, an advanced ability to formulate their own hazard assessment, and of course the requisite gear. It is essential to have a detailed understanding of the snowpack before exposing yourself to avalanche terrain this week especially. There is still relatively limited information available, so head out with a cautious assessment mindset.
The alpine has received over a metre of new snow in many zones, especially the high glaciated ares. Crevasses will be well concealed by abundant new snow, which is not as consolidated as the same depth of snow later on in the season. This comes after a summer of record-breaking glacial recession, so expect big changes and new crevasses in areas you might now expect them to be. Be fully prepared to deal with crevasse hazard in the coming weeks.
While the alpine has received a lot of snow, at lower elevations this has not been so much the case with a lot of rain and warmer temperatures. Early season buried hazards remain a concern, including rocks, branches and stumps.
WHAT TO DO
Hiking and rock climbing -- I think we can officially strike these activities off the roster of recommended activities for the year. Snowshoeing on trails is a possibility at higher elevations now but conditions are not optimal yet.
Skiing -- I still contend it's too early to get excited about skiing. However it is undeniable that at upper elevations there are great turns to be had. Whether you want to deal with the hazards and effort of getting there is a decision only you can make. Inbounds skiing is probably pretty decent right now for this time of the year.
Ice climbing -- with the warm temps low elevation and sun exposed ice climbs have been slow to start. High elevation shaded aspects are your best bet still.
With AvCan beginning its bulletins next week this is the last MCR Summary of the year. Thanks for tuning in; see you next spring!
Have a safe and wonderful winter.
Mountain Guide ACMG/IFMGA