Lizard-Flathead

Careful terrain selection remains critical even as hazard drops to moderate. Windslabs are highly variable due to changing winds & blowing snow. Remember that even small avalanche can trigger a buried weak layer in a step-down event.  

High pressure influences the region for the forecast period with cool temperatures, isolated flurries, light winds gusting moderate/strong from the northwest, a mix of sun and clouds and a glimpse of more snow near the end of the week.

Sunday night: Cloudy with isolated flurries. Alpine low temperatures near -9C and freezing levels valley bottom. Ridgetop wind light and variable gusting moderate from the Northwest.

Monday: Mostly cloudy with isolated flurries and sun breaks. Alpine high temperatures near -8C and freezing levels valley bottom. Ridgetop wind light and variable gusting moderate from the west/northwest.

Tuesday: Mix of sun and cloud. Alpine high temperatures near -11 and freezing levels valley bottom. Ridgetop wind light and variable gusting moderate from the northwest.

Wednesday: Mix of sun and cloud with isolated flurries. Alpine high temperatures near -10 and freezing levels valley bottom. Ridgetop wind moderate from the southwest gusting strong from the west.

Early reports from Sunday comment on being able to trigger small windslab avalanches, although they are getting harder to trigger. From Saturday there were reports of several intentionally triggered small (size 1) soft wind slab avalanches and a small (size 1) explosive triggered avalanche from a cross-loaded alpine feature at treeline. Sluffing of loose dry snow is building mass to size 1 from steep wind sheltered terrain. 

A nearby neighbour reported a large avalanche (size 2) that imitated 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. On Wednesday there were numerous storm slabs up to size 1.5 that were triggered with explosives. This MIN from Tunnel creek on Dec 24th also reports numerous large avalanches on cross loaded features at treeline. On Tuesday, a widespread natural avalanche cycle up to size 3 was reported from the lizard range with many avalanches reported from northerly aspects. 

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

30-60 cm that fell earlier in the week has been blown by moderate to strong winds in exposed treeline and above since then. Moderate to strong west and southwestern winds created significant ridgetop snow re-distribution onto lee slopes. 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. 

Recent snow fell on a variety of old surfaces including a buried melt-freeze crust reported below 1700m and surface hoar reported around treeline. This Min from Mt. Fernie on Dec 26th found 5-15cm of low density snow above this recent crust while this Min near Tunnel Creek found it down 20cm. This MIN from Lodgepole reports this near surface thin crust disappearing above 1800m.

Buried 60-130cm one can find a variety of weak layers from early December. This persistent weak layer, with facetted crystals and surface hoar crystals above is starting to gain strength. This MIN from the 27th near Mongolia Bowl reports finding this crust at 60cm with no notable results in their test pits while this MIN form the 26th saw varying results - including a deep hard result on basal layers.

Deeper in the snowpack are two hard melt-freeze crusts that formed in November that may have some weak crystals around them. This potential avalanche problem is dormant at this time, however; it 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.

• Pay attention to the wind, once it starts to blow fresh sensitive wind slabs are likely to form.
• Expect slab conditions to change drastically as you move into wind exposed terrain.
• Approach lee and cross-loaded slopes with caution.
• If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
• Minimize your exposure time below cornices.