Avalanche Forecast

Issued: Jan 18th, 2019 4:58PM

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

shorton, Avalanche Canada

Purcells.

The Purcell snowpack is still scary and requires conservative terrain choices. Read the Forecaster's Blog about the region for more details here...

Summary

Confidence

High -

Weather Forecast

FRIDAY NIGHT: 5-10 cm of snow, moderate southwest wind, alpine temperatures drop to -10 C.SATURDAY: Flurries easing throughout the day with another 5 cm of snow, strong southwest wind, freezing level climbing to 1200 m, alpine high temperatures around -5 C.SUNDAY: Mostly cloudy then clearing in the afternoon, moderate west wind, freezing level climbing to 800 m, alpine high temperatures around -7 C.MONDAY: Mix of sun and cloud, light northwest wind, alpine high temperatures around -8 C.

Avalanche Summary

The likelihood of triggering large avalanches is still 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.On Thursday, explosives triggered numerous large cornices on north alpine ridges. On Wednesday, a large (size 3) naturally triggered avalanche was observed on a southeast aspect in the alpine near Golden. 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.Last weekend, 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.

Snowpack Summary

The snowpack is weak and touchy in large portions of the Purcells, with very large avalanches being reported on a regular basis. This type of weak snowpack could stick around for months. Read more here. 5-20 cm of new snow is burying large surface hoar crystals and/or sun crusts, which could eventually develop into a touchy problem as snow accumulates. The most suspect terrain features will be steep slopes and rolls below 2000 m (where the largest surface hoar exists) and steep south-facing slopes in the alpine (where sun crusts 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.Watch for signs of instability such as whumpfing, cracking, or recent avalanches.Minimize exposure to overhead avalanche terrain, large avalanches may reach run out zones.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2.5 - 3.5

Wind Slabs

New snow is gradually accumulating above weak surface hoar and/or crusts. Wind loaded slopes may have enough snow above this layer for small avalanches.

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

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 1.5

Valid until: Jan 19th, 2019 2:00PM