Avalanche Forecast

Issued: Feb 9th, 2019 6:41PM

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

Avalanche Canada ghelgeson, Avalanche Canada

Wind slabs may remain sensitive to human triggering in the alpine and there is potential for large avalanches at and below treeline due to the presence of a persistent slab problem. Check out our forecater's blog that goes into more detail here.

Summary

Confidence

Moderate - Wind effect is extremely variable

Weather Forecast

Cold, dry, arctic air continues to dominate the weather pattern for the foreseeable future.SATURDAY NIGHT: Freezing level at valley bottom, around -20 C in the alpine, light variable winds at most elevations with moderate northeast wind at ridgetop that should diminish through the night, no significant snowfall expected.SUNDAY: Mostly clear skies, freezing level at valley bottom, around -20 C in the alpine, light variable wind at all elevations, no significant snowfall expectedMONDAY: Clear skies at dawn with cloud cover increasing throughout the day, freezing level at valley bottom, around -20 C in the alpine, light southerly wind at all elevations, no significant snowfall expected. A trace of snow possible Monday night.TUESDAY: Scattered cloud cover, freezing level at valley bottom, around -20 C in the alpine, light variable wind at all elevations, a trace of snow possible.

Avalanche Summary

On Friday avalanches failed on the mid-January surface hoar to size 1 on north and northeast facing slopes between 1700 and 2000 m. The persistent weak layer that was buried in mid January continues to be reactive to human triggers. Human triggered avalanches up to size 2.5 have been reported almost everyday in the last week. This layer is sensitive enough for avalanches to be triggered remotely (from a distance). This layer has been the most reactive at treeline and below, although there have been a few reports of its presence in isolated sheltered areas in the alpine. Click here to see a Mountain Information Network post that described conditions in Allen Creek on Wednesday.Strong to extreme north, northeast and east wind over the last 72 hours has created wind slabs that may remain sensitive to human triggering in wind exposed features. Checkout this great MIN here from Friday.

Snowpack Summary

30-60 cm of old storm snow is sitting on surface hoar (feathery crystals), facets (sugary snow) and a crust on sun-exposed slopes. In many areas, recent strong winds have redistributed the new snow and formed wind slabs on all aspects due to shifting wind directions.The most notable feature in the snowpack is a persistent weak layer that was buried in mid January, which is now 50-80 cm below the surface. This layer consists of surface hoar and a crust on sun-exposed slopes. It is most prominent at treeline and below, and continues to produce avalanches.

Problems

Wind Slabs

An icon showing Wind Slabs
Many locations have been hit hard by winds over the last few days forming wind slabs in the lee of terrain features on a variety of aspects. Strong to extreme wind out of the north, northeast and  east has likely formed slabs in unusual locations.
If triggered, wind slabs may step down to deeper layers and result in even larger avalanches.Avoid areas where the snow feels stiff and/or slabby.Back off if you encounter whumpfing, hollow sounds, or shooting cracks.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Persistent Slabs

An icon showing Persistent Slabs
50-80 cm of snow sits above a weak layer of surface hoar and crust that was buried in mid January. This layer continues to be reactive to human triggering. The trees are not a safe haven this weekend.
Any steep opening in the trees should be treated as suspect right now.Use conservative route selection, choose moderate angled and supported terrain with low consequence.Avoid convexities as well as steep, open and/or sparsely treed slopes at and below treeline.

Aspects: All aspects.

Elevations: Treeline, Below Treeline.

Likelihood

Possible

Expected Size

1.5 - 3

Valid until: Feb 10th, 2019 2:00PM

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