Avalanche Forecast
Issued: Jan 9th, 2022 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Persistent Slabs.
ldreier,
Avalanche Canada
Strong southwest wind will continue to form wind slabs in lee terrain features. Activity on the early Dec persistent weak layer increased over the weekend. Avoid rocky shallow snowpack and thin to thick transitions where triggering is more likely.
Summary
Confidence
Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.
Weather Forecast
Sunday night: Clear, strong southwest wind gusting to extreme, treeline low around -8 °C, freezing level at valley bottom.
Monday: Sunny, strong southwest wind gusting to extreme, treeline high around -3 °C, freezing level at valley bottom.
Tuesday: Mostly cloudy, 5 cm new snow, strong southwest wind gusting to extreme, treeline high around -1 °C, freezing level rising to 1800 m.
Wednesday: Mostly cloudy, 5 cm new snow, strong southwest wind gusting to extreme, treeline high around +2 °C, freezing level rising to 2200 m.
Avalanche Summary
On Friday, explosives and skiers easily triggered storm slab avalanches to size 1.5.
On Wednesday, explosive control work produced numerous loose dry and thin wind slab avalanches in alpine terrain. These avalanches started small but entrained mass in tracks, growing to size 2.5 and running up to 1300m. It is worthy to note that no deep slabs were triggered.
The persistent slab problem has produced sporadic and spotty activity in the South Rockies and nearby regions. The activity increased over the past weekend.Â
- On Saturday, Jan 8, explosives triggered a very large (size 4) deep persistent slab avalanche at 2100 m on a SE aspect. The avalanche failed 1-2 m deep on the early December layer.Â
- On Friday, a large (size 2.5) natural deep persistent slab avalanche released in the west of the region and was reported in this MIN post.
- The last activity before that occurred on Dec 31, when explosives triggered a size 2.5 wind slab avalanche that stepped down to the persistent weak layer on a SE aspect near treeline.Â
A few recent notables from surrounding regions feature in our latest blog, Photos of recent persistent slab avalanches in the southern interior.
Snowpack Summary
The recent storm snow totals 40-70 cm. Strong southwest to southeast winds have developed more reactive deposits around convex and lee features. This recent snow covered a hard, faceted snow surface which formed during cold temperatures, and may take a little time to bond.Â
The most notable layer of concern in the snowpack is a crust that was formed in early December and is now typically down 80-150 cm. Activity on this layer has been sporadic, the most recent persistent slab avalanche in the region was on Saturday, January 8. This layer has created a tricky low likelihood, high consequence scenario which is best managed through conservative terrain choices and disciplined backcountry travel techniques.
Terrain and Travel
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Be aware of the potential for large avalanches due to the presence of a persistent slab.
- Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
Problems
Wind Slabs
Strong southwest wind continues to redistribute the recent new snow. More reactive deposits will be found on convex rolls and leeward terrain below ridges. The strong wind might form wind slabs lower down slope than expected. The recent snow may overlie a weak interface which could result in deeper and touchier than expected slabs.
Aspects: North, North East, East, South East, North West.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
A persistent slab problem formed by a crust down 80-150 cm has created a low likelihood, high consequence scenario that is difficult to forecast. Avoid likely trigger spots such as steep, rocky slopes with a shallow or thin to thick snowpack.
The same feature or path can slide repeatedly when the persistent weak layer gets reloaded by new snow.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Jan 10th, 2022 4:00PM
