Avalanche Forecast

Issued: Jan 25th, 2018 4:12PM

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

jfloyer, Avalanche Canada

North Columbia.

There mountains are currently covered with a dangerous snowpack making safe travel difficult. There have been numerous reports of recent natural and human-triggered avalanches. Simple terrain is your friend.

Summary

Confidence

Moderate - Timing of incoming weather systems is uncertain on Sunday

Weather Forecast

Friday: Mostly dry and cool. Treeline temperatures around -8C. Light southwesterly winds.Saturday: Light snow, 5-10 cm. Treeline temperatures around -7C. Light southwesterly winds.Sunday. Snow, heavy at times. 15-20 cm. Freezing level rising to 1200 m. Strong southwesterly ridgetop winds.

Avalanche Summary

Wednesday was a particularly active day in the mountains. There were numerous reports of natural and human triggered avalanches in storm snow (up to size 2.5) and on persistent weak layers (up to size 3.5). Avalanches have been reported on all aspects. Most releases have been reported from elevations above 1800 m although some skier-triggered avalanches have been reported from lower elevations. There were similar reports from Tuesday and this follows a continued trend of recent heightened avalanche activity.I anticipate the amount of natural avalanche activity to decline into Friday and Saturday, but human-triggered avalanches will remain likely.

Snowpack Summary

The current snowpack is complex, with three active weak layers that we are monitoring.60-90 cm of storm snow sits on a layer of crust and/or surface hoar from mid-January. The crust is reportedly widespread, with the possible exception of high elevation north aspects. The mid-January surface hoar is 5 to 20 mm in size and was reported at treeline elevations and possibly higher. The recent storm snow fell with strong south winds, producing wind slabs in lee features at treeline and alpine elevations and in open areas below treeline.Deeper in the snowpack, the early-January persistent weak layer is 80 to 100 cm below the surface. It is composed of surface hoar on sheltered slopes as well as sun crust on steep solar aspects and is found at all elevation bands. Snowpack tests show sudden fracture characters with moderate loads and high propagation potential, and signs of instability such as whumpfs and cracking. Another weak layer buried mid-December consisting of a facet/surface hoar/crust combination is buried 100 to 150 cm deep. It is most problematic at and below tree line.A rain crust buried in November is generally 150 to 200 cm deep and is likely dormant for the time being.

Problems

Storm Slabs

Up to 80 cm of recent snow has formed a slab that sits on a weak layer of surface hoar and/or a crust. Expect the slab to be especially deep and reactive to human triggering in lee features due to recent strong south winds.

If triggered, storm/wind slabs may step down to deeper layers and result in large avalanches.Be very cautious as you transition into wind affected terrain, wind slabs may be deep and touchy.Be aware of the potential for wide propagations.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 3

Persistent Slabs

Three weak layers are lurking in our snowpack that continue to produce very large avalanches. Use extreme caution in areas where weak layers may be preserved, such as in openings below treeline, and sheltered areas in the alpine and treeline.

Avoid open slopes and convex rolls where buried surface hoar may be preserved.Use conservative route selection, choose moderate angled and supported terrain with low consequence.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

2 - 3.5

Valid until: Jan 26th, 2018 2:00PM