Avalanche Forecast Cariboos

Friday 8th February 2019

Avalanche Danger Ratings Fri 8th Feb 5:09PM Danger Ratings Alpine: Moderate Danger Ratings Treeline: Considerable Danger Ratings Below Treeline: Considerable Persistent Slabs Persistent Slabs Wind Slabs Wind Slabs

Avalanche Canada Forecaster: ghelgeson

Date Issued:

Valid Until:

There is potential for triggering large avalanches treeline and below due to the presence of a persistent slab problem. Click here to see our Forecasters' Blog for a more detailed description of current conditions.

Confidence

Moderate -

Weather Forecast

Cold, dry, arctic air continues to dominate the weather pattern for the foreseeable future.FRIDAY NIGHT: Freezing level at valley bottom, around -25 C in the alpine, potentially strong valley bottom wind event, moderate to strong east/southeast wind in the alpine, no significant snowfall expected. SATURDAY: Clear skies, freezing level at valley bottom, around -25 C in the alpine, light winds at most elevations, light to moderate east/northeast wind at ridgetop, no significant snowfall expected.SUNDAY: Clear skies, freezing level at valley bottom, around -20 C in the alpine, potentially strong valley bottom wind event, light southeast wind in the alpine, no significant snowfall expectedMONDAY: Clear skies, freezing level at valley bottom, around -20 C in the alpine, light variable wind at all elevations, no significant snowfall expected.

Avalanche Summary

A persistent weak layer that was buried in mid January continues to be reactive to human triggers. This layer is sensitive enough for avalanches to be triggered remotely (from a distance). Human triggered avalanches up to size 2.5 were reported on Sunday, Monday and Wednesday. 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.Several wind slab avalanches to size 1.5 were reported running on a variety of aspects in the alpine on Wednesday.

Snowpack Summary

30-60 cm of recent new 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 at this time is a persistent weak layer that was buried in mid January, which is now buried 50-80 cm. 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.

Persistent Slabs Persistent Slabs

Likelihood

Likely - Possible

Expected Size

1.5 - 3

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 right now.

Use conservative route selection, choose moderate angled and supported terrain with low consequence.Any steep opening in the trees should be treated as suspect right now.

Aspects: All aspects.

Elevations: Treeline, Below Treeline.

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Wind Slabs Wind Slabs

Likelihood

Possible

Expected Size

1 - 1.5

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.  East, southeast and northeast wind Friday night into Saturday could form slabs in unusual locations.

Be careful with wind loaded pockets, especially near ridge crests and roll-overs.If triggered, wind slabs may step down to deeper layers and result in even larger avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

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