Avalanche Forecast

Issued: Jan 27th, 2016 8:09AM

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

triley, Avalanche Canada

South Columbia.

Warm, Wet, and Windy storm will create new wind slabs and add load above the persistent weak layer. Conservative terrain use recommended at this time.

Summary

Confidence

Moderate - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

Freezing levels are uncertain overnight. Most products are suggesting that freezing levels will rise up to about 1700 metres, however there is a chance that freezing levels may rise as high as 2200 metres. This is more likely in the west of the region. Expect 5-10 cm of new snow in the alpine combined with strong winds overnight. Snow and strong wind continuing on Thursday with 10-20 cm forecast during the day. Freezing levels dropping down below 1000 metres on Friday as winds decrease to light southerly and periods of light snow continue. Light winds and freezing level near valley bottoms on Saturday with flurries or light snow.

Avalanche Summary

No new natural avalanches were reported on Tuesday. Some small avalanches up to size 1.5 were reported to be remotely or accidentally triggered on Tuesday. Natural avalanches up to size 3.0 were reported on Monday in the southern Monashees, and up to size 2.5 in the southern Selkirks. Numerous slab avalanches up to size 3 were reported over the weekend. Most of the natural avalanche activity occurred on Friday and Saturday but several were still reported on Sunday.

Snowpack Summary

Wind slabs continue to develop in the alpine and at treeline. In some areas these new wind slabs may be sitting on a layer of surface hoar. In other areas wind probably destroyed the surface hoar, or freezing drizzle created a thin crust at the beginning of the storm. I have continued to call the avalanche problem a wind slab, due to the widespread nature of the strong southwest winds. A thin new storm slab may exist in some areas in the south of the region. The persistent weak layer that was buried in early January is now down about 50-100 cm. This thick persistent slab overlies a variety of surfaces including large surface hoar, sun crusts, rime crusts and facets. The slab is ripe for human and natural triggers and is especially touchy at and below treeline. Rising freezing levels may increase the likelihood of triggering the persistent slab in the short term.

Problems

Wind Slabs

Wind slabs continue to develop due to strong southerly winds and new snow. Thin storm slabs may develop in sheltered areas.

Use ridges or ribs to avoid wind loaded slopes. >Avoid freshly wind loaded features. >Be cautious as you transition into wind affected terrain. >

Aspects: North, North East, East, South East.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Persistent Slabs

Natural activity may have stopped on this weak layer, however human triggering continues to be likely. Remote triggering and long fracture propagations are also likely with this persistent weak layer.

Be aware of thin areas that may propogate to deeper instabilites.>Use conservative route selection and be aware of the possibility of remote triggering.>Avoid steep open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

2 - 5

Valid until: Jan 28th, 2016 2:00PM