Avalanche Forecast

Mild cool weather for the forecast period with a mix of sun and clouds with isolated flurries. Winds will increase moderate to strong from the northwest switching to south west. The next notable precipitation looks like the end of the week.  

Sunday night: Mainly cloudy with clear periods. Alpine low temperatures near -7C and freezing levels valley bottom. Ridgetop wind increasing moderate to strong from the west/northwest. 

Monday: A mix of sun and clouds. Alpine high temperatures near -3C and freezing levels valley bottom. Ridgetop wind moderate to strong from the west/northwest. Mild alpine temperature inversion with cool cloudy valleys and warmer clear skies above. 

Tuesday: Increasing clouds with isolated flurries in the afternoon. Alpine high temperatures near -3C and freezing levels valley bottom. Ridgetop wind increase to strong gusting extreme from the southwest.  

Wednesday: Mainly cloudy with sun breaks and isolated flurries. Alpine high temperatures near -3C and freezing levels valley bottom. Ridgetop wind easing to light to moderate from the west/southwest. 

No new reports from recent days, though ongoing evidence of the Christmas Eve cycle are being reported, such as in this MIN reporting many large (size 2) windslabs just below ridgecrest. The largest reported avalanche (size 2.5) appeared to step-down to the December rain crust.  

Earlier in the week at the height of this cycle, there were many reports of small to large (size 1-2) windslab avalanches with a few very large avalanches (size 2.5) that stepped down the the December crust. Last Sunday a human triggered slab avalanche size 2 was reported near Little Simpson. It appears to have started as a wind slab or storm slab and then stepped down to the early December persistent weak interface. Though avalanche hazard is decreasing, human triggered avalanches remain possible and the consequence of a large destructive avalanche high.

A MIN report submitted on Tuesday showed a deep release from a leeward high alpine feature off the north side of Hudson Mountain. The deep persistent slab problem may be isolated, however it is very high consequence if you find yourself involved in an avalanche of this size.

Recent winds and light snow earlier this week have scoured some areas and have built wind slabs in others. On Christmas Eve, strong winds from the south west loading lee north and east aspects. On Christmas Day winds shifted to the east loading lee north and wast aspects. As winds shift back to the west be on the look out for buried windslabs, cross loading or reverse loading patterns. This wind effect will be most apparent in exposed regions at treeline and above but may extend to open areas below treeline.  

Cornices have grown large with recent variable winds. These represent a hazard underfoot along ridgecrests but are most problematic when they collapse above wind loaded avalanche paths and can initiate large avalanches. 

While much of the region received 5-15cm in the recent storms, some of the higher more mountainous areas may have received up to 30cm. In wind sheltered locations, there is now about 30-70 cm of snow above an early-December melt-freeze crust with weak and sugary faceted grains around it. This layer bay be deeper in deeper snowpack or wind-loaded areas - as reported from Hankin. This early December crust layer has featured in several avalanche reports from Dec 19th and Dec 17th in Hankin. This interface was reactive to human triggering in the last week, continue to show up in snowsuit tests and produced size 2 avalanches with the past week. 

A crust that was buried in early November sits near the base of the snowpack. This crust has weak facets associated with it. These facets have produced large avalanches in both the south and north of the region. This MIN report from December 22 highlights a deep release avalanche and the variable snowpack depths.

Snowpack depths vary substantially with aspect, elevation, and wind exposure.

• Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
• If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
• In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.
• Be alert to conditions that change with elevation, aspect and exposure to wind.