Avalanche Forecast

Issued: Jan 15th, 2019 5:19PM

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

shorton, Avalanche Canada

Purcells.

Triggering large avalanches remains a serious concern in the Purcells. Read more here in the Forecaster's Blog. Conservative terrain selection is highly recommended.

Summary

Confidence

High -

Weather Forecast

TUESDAY NIGHT: Cloudy with clear periods, light wind, alpine temperatures drop to -12 C.WEDNESDAY: Mix of sun and cloud, light southwest winds, alpine high temperatures around -6 C.THURSDAY: Cloudy with light snowfall (2-4 cm), light south wind, alpine high temperatures around -8 C.FRIDAY: Mostly cloudy, trace amounts of snow, light southwest wind, alpine high temperatures around -6 C.

Avalanche Summary

No new avalanches were reported on Tuesday.On Monday, several large (size 2) avalanches were observed throughout the region, some releasing on weak faceted grains near the base of the snowpack.On Sunday, a large (size 3) avalanche ran full-path on a southwest aspect in the alpine near Golden. It also released weak snow near the base of the snowpackOn Saturday, a group of snowmobilers triggered a fatal avalanche near Invermere, also on the basal weak faceted grains. The avalanche was on a southerly aspect and ran approximately 900 to 1100 m. Two snowmobilers were caught. See here for more information.On Friday, five large to very large (size 2 to 3.5) deep persistent slab avalanches were observed on various aspects in alpine terrain.The likelihood of triggering large avalanches is elevated due to the weak nature of the snowpack. Watch out in thin snowpack areas, where the likelihood of triggering deeper layers is the highest. Check out a few of the other recent large and destructive avalanches triggered by people via MIN posts here and here.

Snowpack Summary

The snowpack is weak and touchy in a large portion of the Purcells. Numerous very large avalanches have been reported daily. This is the type of weak snowpack that could stick around for months. Read more here. At the top of the snowpack, recent warm air and sunny skies may have produced a crust on the snow surface. Expect to find a sun crust on southerly aspects and possibly a temperature crust on other aspects. At higher elevations in exposed terrain, wind slabs may still exist.The weak nature of the snowpack lies at depth. There is a weak layer around 80 to 120 cm deep, composed of sugary faceted grains, feathery surface hoar, and a sun crust. The base of the snowpack is also composed of weak faceted grains in many parts of the region. Humans have and will continue to be able to trigger these layers in areas where the snowpack is shallow.

Problems

Deep Persistent Slabs

People have recently triggered destructive avalanches on buried weak layers. This problem will exist for a while to come. These layers are more easily triggered in areas where the snowpack is shallow, such as near ridges and rocky terrain.

Best to avoid steep slopes and areas with a thin, variable snowpack. Avoid overhead exposure.Be aware of the potential for full-depth avalanches due to weak layers at the base of the snowpack.Observe for signs of instability: whumpfing, hollow sounds, shooting cracks, and recent avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

2 - 3.5

Wind Slabs

Wind slabs may linger at higher elevations.

Use caution in lee and cross-loaded terrain. Recent wind-loading has created wind slabs.If triggered, slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Jan 16th, 2019 2:00PM