Avalanche Forecast
Issued: Jan 24th, 2018 5:07PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Persistent Slabs.
cgarritty,
Avalanche Canada
The snowpack in the Columbias is both complex and dangerous. Watch for wind loaded areas in the alpine but be especially wary of sheltered terrain at all elevations. This shelter is what has preserved our deeply buried weak layers.
Summary
Confidence
Moderate - Forecast snowfall amounts are uncertain
Weather Forecast
Wednesday night: Flurries bringing 5-10 cm of new snow. Light to moderate south winds.Thursday: Mainly cloudy with continuing scattered flurries bringing approximately 5 cm of new snow. Light southwest winds. Alpine high temperatures around -8.Friday: Cloudy with scattered flurries and 2-5 cm of new snow. Light southwest winds. Alpine high temperature to -9.Saturday: Cloudy with flurries bringing 5-10 cm of new snow. Light southeast winds. Alpine high temperatures to -8.
Avalanche Summary
Reports from Tuesday included numerous storm slab and wind slab releases ranging from Size 1-2, as well as several more persistent slab releases ranging from Size 2-2.5. This activity occurred on all but southwest aspects and mainly above 2100 metres. One persistent slab was skier triggered on the late November layer, down only 60 cm in an alpine location west of the Valhallas.On Monday, there were many reports of Size 1-2 storm slabs triggered by skiers, generally on northerly and easterly aspects at all elevation bands. Below treeline, avalanches were releasing in open cutblocks. There were also numerous reports of large (size 2 to 3) persistent slab avalanches being triggered naturally and by skiers on northerly and easterly aspects, at treeline and alpine elevations, releasing on the early-January weak layer. There was one report of a very large avalanche (size 3.5) releasing on either the mid-December layer or the November layer.Similar avalanches have been observed daily since last Wednesday. 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 be especially deep and reactive to human triggering in lee features due to recent strong south winds.
Avoid exposure to terrain traps where the consequence of a small avalanche could be serious.Be very cautious as you transition into wind affected terrain, wind slabs may be deep and touchy.If triggered storm/wind slabs may step down to deeper layers and result in very large avalanches.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
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.
Good day to make conservative terrain choices and watch for clues of instability.Avoid open slopes and convex rolls where buried surface hoar may be preserved.Be very cautious in open terrain features, such as cutblocks, gullies, and cutbanks.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Jan 25th, 2018 2:00PM
