Avalanche Forecast

Issued: Nov 30th, 2018 3:14PM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is low. Known problems include Persistent Slabs.

ghelgeson, Avalanche Canada

Kootenay Boundary.

There is a lot of uncertainty with the buried surface hoar layer down 40 to 80 cm. Human triggered avalanches are most likely at treeline and on sheltered alpine features. See our new Fx'rs Blog here for some insight into managing this problem.

Summary

Confidence

Low - Due to the number of field observations

Weather Forecast

We areÂ transitioning into a period of pronounced high pressure. The forecast period is marked by cooler temps, the potential for sunny periods and a lack of significant precipitation, even in the extended forecast.FRIDAY NIGHT: Freezing level around valley bottom, light west wind, a trace of snow possible. SATURDAY: Scattered cloud cover, freezing level around 900 m, light northeast wind, no significant precipitation expected.SUNDAY: Scattered cloud cover, freezing level around valley bottom, light variable wind, no significant precipitation expected.MONDAY: Scattered cloud cover, freezing level at valley bottom, light variable wind, no significant precipitation expected.

Avalanche Summary

No new avalanche observations from this week. Two MIN reports from Saturday November 24th are worth your consideration though:This one describes a rider getting caught and carried in a small storm slab in the Ymir bowl area. This one details a group of riders triggering a large deep persistent slab avalanche in Meadow Creek which is in the neighboring South Columbia region. Multiple folks were involved, but thankfully everyone survived.Huge thanks to everyone posting to the MIN, please continue to do so here.

Snowpack Summary

The storm that arrived Sunday night delivered 20 to 40 cm of snow that has settled out to about 30 cm of soft snow. At treeline the total height of snow is now between 100 and 140 cm. 40 to 80 cm below the surface lies a persistent weak layer that was buried on November 21st. This weak layer consists of surface hoar (feathery crystals) in most places, but may present as a sun crust on steep south facing slopes. This layer has been reactive in snowpack tests this week. Check out this MIN from Thursday that talks about it. This surface hoar is thought to be widespread at treeline and it may be found in sheltered alpine features too. A recent MIN report suggests that this layer was producing obvious signs of weakness at Kootenay Pass on Tuesday.At the base of the snowpack is a thick melt-freeze crust that formed near the end of October. This crust has shown limited reactivity thus far, but observations are very limited.

Problems

Persistent Slabs

The recent storm snow is consolidating into a slab that rests on a persistent weak layer 40 to 80 cm below the surface. This layer seems to be most prevalent at treeline, but likely extends into the alpine in sheltered terrain too.

Smaller avalanches in motion may step down to deeper layers resulting in large avalanches.Avoid open slopes and convex rolls at treeline where buried surface hoar may be preserved.Back off if you encounter signs of instability such as whumpfing, cracking, or recent avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 2.5

Valid until: Dec 1st, 2018 2:00PM