Avalanche Forecast

Issued: Jan 27th, 2019 4:39PM

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

North 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 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

Over the last five days storm and persistent slab avalanches averaging size 2 have released naturally and been human triggered on the mid-January surface hoar which is 25 to 50 cm below the surface. The majority of these avalanches occurred at treeline and below, however, there have been a few noted at higher elevations in the alpine. On Saturday wet loose avalanches to size 2 were reported on south facing aspects between 1800 and 2500 m during the heat of the daytime warming. Wind slab avalanches to size 2 were also reported on a variety of aspects between 1700 and 2700 m.There were a few reports of remote triggering Friday on north, northwest and east facing slopes. One was triggered from a flat ridge 30 m away from the avalanche which ran on a moderately inclined north facing slope at 1900 m producing a size 2.5 avalanche.

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 50 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 50 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.

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 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.

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.

Likelihood

Possible

Expected Size

2 - 2.5

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