Avalanche Forecast

Issued: Jan 12th, 2019 4:53PM

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

ghelgeson, Avalanche Canada

South Rockies.

A big rise in freezing levels may mean that the deep persistent slab wakes up. A lot of uncertainty exists as to what this layer will do as temperatures climb. High levels of uncertainty are best managed by choosing conservative terrain.

Summary

Confidence

Low - Freezing levels are uncertain

Weather Forecast

A classic temperature inversion sets up Saturday night which will likely stick with us until Tuesday.Â No significant precipitation is expected until possibly Friday.SATURDAY NIGHT: Temperature inversion with cold (below freezing) air in the valleys and above freezing temperatures between 1500 and 3200 m, light to moderate south/southwest wind, no precipitation expected.SUNDAY: Clear skies, temperature inversion with cold (below freezing) air in the valleys and above freezing temperatures between 1600 and 3000 m, light northwest wind at most elevations with moderate northwest wind at ridgetop, no precipitation expected.MONDAY: Clear skies and warm with the freezing level at 3000 m, light variable wind, noÂ precipitation expected.TUESDAY: A few clouds, freezing level at valley bottom, light variable wind, no precipitation expected.Â

Avalanche Summary

On Friday we received a great Mountain Information Network observation of natural activity on solar aspects, more details here.Â A size 2-2.5 natural avalanche was also reported on a north aspect at 2200 m on Friday. This avalanche was likely triggered by a rock fall, and ran on the deep persistent layer at the base of the snowpack.A few size 1 natural and explosives triggered avalanches were reported in the region on Thursday.

Snowpack Summary

10-20 cm of recent storm snow has been redistributed by strong winds and has formed wind slabs at upper elevations. This new snow sits on previous hard wind slabs, a scoured and shallow snowpack on exposed ridges, and soft snow in sheltered areas. Large variability in snow depths still exists in the region, ranging from almost no snow to nearly 200 cm in some areas. For average snowpack areas, expect to find weak and sugary faceted snow around 50 to 100 cm deep, which extend to the ground. This weak bottom half of the snowpack has been the culprit for large avalanches in the region over the past few weeks. Warming temperatures and sunshine over the coming days could re-activate this layer, resulting in a possible avalanche cycle.

Problems

Deep Persistent Slabs

Deeply buried weak layers remain a concern, especially as temperatures rise and the sun comes out. Large loads like cornices may trigger this layer as well, and cornice failures become more likely during warm, sunny conditions.

Watch for clues, like sluffing off of cliffs, that the snowpack is warming up. Pay attention to overhead hazards like cornices which could trigger the deep persistent slab.Use conservative route selection, choose moderate angled and supported terrain with low consequence.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 3

Storm Slabs

Slabs may become more reactive as temperatures rise and the sun comes out.

If triggered the storm slabs may step down to deeper layers resulting in large avalanches.Minimize exposure to steep slopes on warm or sunny days.Be careful with wind loaded pockets, especially near ridge crests and roll-overs.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Jan 13th, 2019 2:00PM