Avalanche Forecast

Issued: Jan 29th, 2017 4:12PM

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

Avalanche Canada rbuhler, Avalanche Canada

Thin new wind slabs are expected to be touchy on Monday. Use extra caution in wind exposed terrain and watch for signs of recent wind loading.Persistent slab avalanches remain a serious concern and conservative terrain selection is very important.

Summary

Confidence

Moderate - Wind effect is extremely variable

Weather Forecast

5-15 cm of new snow is expected Sunday night before an Arctic front moves southwards on Monday bringing a return to cold and dry conditions which is expected to persist for several days. A mix of sun and cloud is expected on Monday with treeline temperatures around -10C and the possibility of lingering flurries in the morning. Alpine wind is forecast to be moderate to strong from northwest in the morning and ease off in the afternoon. Mostly sunny conditions are forecast for Tuesday and Wednesday with light alpine wind from the northeast and treeline temperatures around -15C.

Avalanche Summary

On Saturday, a natural size 3 avalanche was reported west of Valemount on a northeast aspect at 2400 m elevation. A MIN report from Saturday describes a large avalanche west of McBride. Click here for more details. On Monday, ongoing moderate to strong wind with small amounts of new snow from Sunday night is expected to continue to develop touchy new wind slabs. Recent wind has been from variety of aspects and wind slabs should be expected on all aspects. Persistent slab avalanches also remain a serious concern for the region. Last week there were numerous large human triggered avalanches and several of these avalanches involved multiple people being buried. These avalanches all released on or stepped down to the mid-December weak layer down 1-1.5 m in the snowpack. Check out the MIN posts for more details and photos of these large, human triggered avalanches. Click here for an example of a persistent slab avalanche that was triggered in fairly mellow terrain.

Snowpack Summary

50-70 cm of old snow has settled over the mid-January interface which consists of buried surface hoar in sheltered areas, old wind slabs in exposed terrain, and/or widespread faceted old snow. The interface has generally stabilized but isolated weaknesses may still exist where buried surface hoar is preserved. Ongoing moderate to strong winds in exposed terrain have been forming new wind slabs over the weekend. The new snow and strong winds on Sunday night are expected to add additional load to these touchy wind slabs. The mid-December surface hoar/facet weakness is now found down 50 cm in shallow snowpack areas, or as much as 1.5 m in deeper snowpack areas. This layer woke up during the last storm and has remained reactive to human triggers. This weak layer is responsible for several large human-triggered avalanches, including some with multiple burials, and this sensitivity is expected to continue for the foreseeable future.For more information, check out this video of our field team testing the snowpack near Barkerville: https://vimeo.com/201318688 or click here.

Problems

Wind Slabs

An icon showing Wind Slabs
Thin new wind slabs have formed over the weekend and wind loading is expected continue to on Monday. Recent winds have been from a variety of directions and wind slabs should be expected on all aspects in wind exposed terrain.
Use caution in lee areas. Recent wind loading has created wind slabs.Avoid areas where the surface snow feels stiff or slabby.Use ridges or ribs to avoid pockets of wind loaded snow.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Persistent Slabs

An icon showing Persistent Slabs
The persistent weakness buried mid-December has been responsible for several large human-triggered slab avalanches and subsequent burials over the past week. These deeper weaknesses can still be triggered with nasty consequences.
Be aware of the potential for large, deep avalanches due to the presence of buried weak layers.Use conservative route selection, choose moderate angled and supported terrain with low consequence.Avoid shallow snowpack areas where triggering is more likely.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

2 - 4

Valid until: Jan 30th, 2017 2:00PM