Avalanche Forecast

Issued: Jan 25th, 2018 4:14PM

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

South Columbia.

There mountains are currently covered with a dangerous snowpack making safe travel difficult. There have been numerous reports of both 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 -6C. Light southwesterly winds.Saturday: Light snow, 5-10 cm. Treeline temperatures around -5C. Light to moderate southwesterly winds.Sunday. Snow, heavy at times. 15-20 cm. Freezing level rising to 1200 m. Strong southwesterly ridgetop winds.

Avalanche Summary

Reports from Tuesday and Wednesday included numerous storm slab and wind slab releases ranging from Size 1-2, as well as several more persistent slab releases ranging from Size 2.5-3. This activity occurred on all aspects and mostly above 1900 m. One persistent slab was skier triggered on the late November layer, down only 60 cm in an alpine location west of the Valhallas.Similar avalanches have been observed daily now for over a week. Expect to see more avalanches where these layers are preserved, such as in sheltered locations in the alpine and treeline elevations and in open cutblocks and gullies below treeline.

Snowpack Summary

70 to 100 cm of storm snow sits on a layer of crust and/or surface hoar from mid-January. The crust is widespread, with the possible exception of high elevation north aspects. The mid-January surface hoar is 5 to 20 mm in size and is likely present at all elevation bands. 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 buried 70 to 110 cm deep. It is composed of surface hoar on sheltered slopes and a sun crust on steep solar aspects and is present at all elevation bands. Recent snowpack tests have shown sudden fracture characters with moderate loads and high propagation potential, as well as other signs of instability such as whumpfs and cracking. Yet another persistent weak layer buried mid-December is 100 to 150 cm deep and consists of a facet/surface hoar/crust combination. It is most problematic at and below tree line.A rain crust buried in November is 150 to 200 cm deep. While generally considered dormant, occasional activity has shown that it may react in alpine areas where it is less deeply buried.

Problems

Storm Slabs

Up to 90 cm of recent snow has formed a slab that sits on weak, feathery surface hoar and/or a crust. Expect the slab to remain reactive to human triggering even during a lull in the storms.

If triggered storm/wind slabs may step down to deeper layers and result in very 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

Possible - Likely

Expected Size

1 - 3

Persistent Slabs

Three weak layers are lurking in our snowpack and 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.Good day to make conservative terrain choices and watch for clues of instability.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

2 - 3.5

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