South Rockies

Windslabs lurk near exposed ridgecrests & are highly variable due to changing winds. Remember that even a small avalanche or cornice collapse can trigger a buried weak layer in a step-down event. Careful terrain selection remains critical even as hazard drops to moderate. 

High pressure influences the region for the forecast period with cool temperatures, moderate winds gusting strong from the west/northwest, a mix of sun and clouds and the hint of more snow by the end of the week.

Sunday night: Clear with cloudy periods. Alpine low temperatures near -10C and freezing levels valley bottom. Ridgetop wind moderate gusting strong from the northwest.

Monday: Mix of sun and cloud. Alpine high temperatures near -9C and freezing levels valley bottom. Ridgtop winds light and variable. A mild temperature inversion may bring valley clouds and warmer clear temperatures above.

Tuesday: A mix of sun and clouds. Alpine high temperatures near -9C and freezing levels dropping to valley bottom. Ridgetop light gusting moderate from the northwest. We may see wind enhancement along the divide leading to strong northwest winds.

Wednesday: A mix of sun and clouds. Alpine high temperatures near -9C and freezing levels dropping to valley bottom. Ridgetop wind moderate gusting strong from the southwest/west.

No new avalanches were reported within the forecast region. However, every region surrounding the south rockies reports a similar story: wind slabs have been reactive (most are size 1 but a few size 2) and sometimes step-down to trigger deeper layers (size 2-3). These windslabs are becoming harder to trigger, but still produce avalanches. Wind slabs have been reactive on fans, cross-loaded features and in reverse loaded terrain. 

 A nearby neighbour reported a large avalanche (size 2) that initated as a windslab or cornice failure and stepped down to the December crust on Friday. Another neighbour reported a large (size 2) windslab from a west aspect from cross-loading from recent variable east winds.  

On Thursday there were reports of small (size 1) and large (size 2) windslabs from explosive control within the region and explosive controlled very large (size 3) avalanches and cornice triggered very large (size 2.5-3) avalanches from adjacent regions. The previous day, numerous natural wind slab avalanches up to size 2 were reported on Wednesday from our field team in the Crowsnest. These were mostly seen from West aspects in the alpine. On Tuesday widespread natural avalanche activity up to size 3 was reported through the region. Many of these avalanches ran deep into their runout zones.

Sluffing of loose dry snow is building mass to size 1 from steep wind sheltered terrain.

Please consider sharing your observations on the Mountain Information Network. Thank you to those that have already submitted this winter!

30-60 cm snow that fell earlier in the week has been blown by moderate to strong winds in exposed treeline and above since then. Much of this wind was west / southwest but variable winds have been reported across the region - including northerly winds. Winds are forecast to shift to northwest overnight and into Monday. Wind slabs will likely remain reactive to human triggers, and are the most reactive during periods of moderate to strong winds. Cornice development may be found along ridgecrests and deep windslabs on lee slopes. 

Below 1800m a rain crust has about 10-20cm of recent snow on top of it. A deeper crust from early December is down 70-100 cm. This persistent weak layer, with facetted crystals and surface hoar crystals above and/or below is showing signs of slowly gaining strength. However, smaller avalanches or a cornice failure may step-down to this weak layer. 

The base of the snowpack consists of a hard melt-freeze crust from early-November that may also have weak crystals around it. This potential avalanche problem remains on our radar. This layer produced very large and destructive avalanches in shallower snowpacks within one of our nearest neighbours in the recent storm, highlighting the need to remain cautious of it in shallow, rocky alpine snowpacks. The most likely spot to trigger it would be on thin and rocky slopes or, like above, from step down avalanches or a cornice collapse.

• Be alert to conditions that change with elevation and wind exposure.
• Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
• Shooting cracks, whumphs and recent avalanches are strong indicators of an unstable snowpack.
• If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
• Avoid exposure to slopes that have cornices overhead.