Avalanche Forecast

Issued: Jan 27th, 2019 4:13PM

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

South Columbia.

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 1400 & 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, but the models are not showing any significant precipitation until Friday.SUNDAY NIGHT: Freezing level at valley bottom, light to moderate north/northwest wind, trace of snow possible.MONDAY: Clear skies at dawn with a bit of cloud building in the afternoon, 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 west/northwest wind, trace of precipitation possible.

Avalanche Summary

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 and wind slab avalanches up to size 2 were reported Tuesday though Friday. 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 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 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 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 between 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

Wind over the last 48 hours has been 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.

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