Avalanche Forecast

Issued: Jan 28th, 2019 3:34PM

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

ghelgeson, Avalanche Canada

South Columbia.

Manage wind slabs by paying attention to how the snow feels underneath your skis/track, and backing off where it feels stiff. Increase your caution at and below treeline, buried surface hoar has been especially touchy between 1400 & 1800 m.

Summary

Confidence

Moderate - Wind effect is extremely variable

Weather Forecast

High pressure, cold temperatures and clear skies should allow for great travel and visibility Tuesday. Cloud cover starts to build back in Wednesday ahead of two storm pulses that should deliver a bit of snow beginning on Friday.MONDAY NIGHT: Freezing level at valley bottom, light northerly wind, no precipitation expected.TUESDAY: Clear skies, freezing level at valley bottom, light variable wind, no precipitation expected.WEDNESDAY: Broken cloud cover, freezing level at valley bottom, mostly light variable wind with moderate northwest wind at ridgetop, trace of precipitation possible.THURSDAY: Broken cloud cover, freezing level at valley bottom creeping up towards 1000 m in the afternoon, light variable wind, 1 to 3 cm of snow possible.

Avalanche Summary

On Sunday wind slabs averaging size 1 to 1.5 failed naturally and were sensitive to human triggering on all aspects between 1600 and 2600 m. One hard slab was remote triggered by a skier in the flats 50 m away from the subsequent avalanche, the wind slab then broke above the skier on a northeast facing feature at 2400 m. On Saturday wind slab avalanches to size 2 were reported from north, northeast, east, southeast and southwest facing features between 1950 and 2600 m. Wet loose avalanches to size 2 were also reported from south facing terrain.Several rider-triggered persistent slab avalanches up to size 2 were reported last week. The persistent slab avalanches were most prevalent between approximately 1200 and 1800 m, although some were noted at higher elevations, including into the alpine. Check out this MIN report for a great overview of conditions including photos.

Snowpack Summary

Saturday delivered warmth and strong to extreme wind out of the west, south, southwest and northwest. This left a crust up to 3 cm thick on steep south and some west facing aspects and redistributed quite a bit of snow into wind slabs in lee features at and above treeline. The warmth also allowed 25 to 45 cm of snow to continue to consolidate above the mid-January persistent weak layer (PWL). This PWL is made up of large surface hoar that is most prevalent at and below treeline, with enhanced reactivity noted between 1400 and 1800 m. On steep solar aspects this interface presents as a crust, there may be locations where the surface hoar actually sits on the crust.The middle and lower portions of the snowpack are generally well-settled and strong.

Problems

Persistent Slabs

25 to 60 cm of snow sits above a weak interface of surface hoar and crust. The recent warm to cold temperature transition has allowed a more cohesive slab to form above the surface hoar which is most prevalent between at and below treeline.

Use extra caution around steep open terrain features, such as cutblocks, gullies and cutbanks.Avoid convex rolls at and below treeline where buried surface hoar may be preserved.Take heed of obvious signs of instability such as whumpfing, shooting cracks and recent avalanches.

Aspects: All aspects.

Elevations: Treeline, Below Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2.5

Wind Slabs

Wind Saturday night into Sunday was out of the west, south, southwest and northwest with more than enough oomph to form wind slabs. These wind slabs may rest on a crust, or perhaps even buried surface hoar near treeline.

Carefully evaluate bigger terrain features on an individual basis before committing to them.Avoid areas where the snow feels stiff and/or slabby.Be careful around freshly wind loaded features, especially near ridge crests and roll-overs.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 1.5

Valid until: Jan 29th, 2019 2:00PM