Avalanche Forecast

Issued: Jan 27th, 2019 5:13PM

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

Cariboos.

Manage alpine 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 1500 & 1800 m.

Summary

Confidence

Moderate -

Weather Forecast

High pressure, cold temperatures and clear skies should allow for great visibility Monday and Tuesday. Cloud cover starts to build back in Wednesday along with a few cm of snow. Thursday and Friday look to be storm days, but total accumulations should be less than 10 cm.SUNDAY NIGHT: Freezing level at valley bottom, light to moderate north/northwest wind, no precipitation expected.MONDAY: Scattered cloud cover, 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, light to moderate west/northwest wind, 1 to 5 cm of snow possible.

Avalanche Summary

On Saturday a skier triggered a small persistent slab avalanche on an east facing feature at 2000 m, failing on the mid-January surface hoar.On Friday numerous small wind slabs 15 to 20 cm in depth were observed on small north facing rolls around 2000 m. There was also a report of a natural avalanche underneath a large cornice, photos here. A few natural wind slabs, storm slabs and dry loose avalanches up to size 2.5 were reported on Wednesday and Thursday on steep slopes on a variety of aspects at treeline and alpine elevations.

Snowpack Summary

Saturday delivered warmth and wind to the region, this MIN report notes strong southwest wind Saturday. In the neighboring North Columbias winds were strong to extreme out of the west, south, southwest and northwest. This left a crust on steep south facing aspects and likely redistributed quite a bit of snow into fresh and potentially deep wind slabs in lee alpine features. The warmth also allowed 15 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 1500 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

15 to 45 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 at and below treeline.

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

Aspects: All aspects.

Elevations: Treeline, Below Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2.5

Wind Slabs

Variable wind over the last 48 hours has had more than enough oomph to form wind slabs. These wind slabs may rest on a crust, or perhaps even buried surface hoar near treeline.

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

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Possible

Expected Size

2 - 2.5

Valid until: Jan 28th, 2019 2:00PM