Avalanche Forecast

Issued: Feb 21st, 2017 4:09PM

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

mgrist, Avalanche Canada

Purcells.

The best riding right now is probably on high north aspects, which is also where the hazard is the highest. Don't let your guard down when searching for fresh powder.If the sun comes out in full force, use extra caution on south slopes.

Summary

Confidence

Moderate - The weather pattern is stable

Weather Forecast

We're into a stable and benign weather pattern with cooling temperatures and isolated flurries.WEDNESDAY: Cloudy with light flurries (local accumulations 5-15cm possible) / Light southwest winds / Freezing levels around 700 m.THURSDAY: Cloudy with sunny breaks and isolated flurries / Light southerly winds / Freezing level 300m / Alpine high temperatures near -8 Celsius.FRIDAY: A mix of sun and cloud and isolated flurries / Light variable winds / Freezing level 200m / Alpine high temperatures near -8 Celsius.

Avalanche Summary

On Monday afternoon we had three spooky large avalanches: one natural and two triggered by humans:1) A Size 2.5 persistent slab (40-75cm thick) near Golden was triggered by a skier on a northeast aspect near 2300m. See here for this great MIN post.2) A Size 3 persistent slab (50-120cm thick) near Golden was remote triggered by a touring party on a southeast aspect near 2300m.3) A Size 2.5 persistent slab (30cm thick) near Invermere ran naturally on a north aspect near 2600m.Storm slabs from recent snowfall remain sensitive to light triggers and have the potential to step down and trigger persistent slab avalanches.

Snowpack Summary

We've had minor snowfall amounts (5-20cm) over the past several days (and higher amounts in the south) with moderate southerly winds in some locations. Expect to find 25-40 cm of more recent snow bonding slowly to buried Feb 15th surface hoar and/or a sun crust, and blown into wind slabs at higher elevations. Storm snow from previous weeks is still bonding poorly to the Feb 3rd surface hoar / sun crust layer, which is now down 60-80 cm. At 2000m and below a melt-freeze crust can be found on almost all elevations and aspects. The sun is starting to pack a punch and can trigger loose snow avalanches mid-day. The sun is also creating a thin crust on steep southerly aspects.A persistent weakness buried mid January is now down 80-150 cm and the November crust is down around 180 cm. These deep persistent weaknesses still have the potential to wake up and become reactive with human triggers. (See MIN post above).

Problems

Storm Slabs

The fresh snow is sensitive to light triggers and particularly deep and touchy on wind-loaded slopes.

If triggered the wind slabs may step down to deeper layers resulting in large avalanches.Avoid freshly wind loaded features.Be alert to conditions that change with elevation.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Persistent Slabs

A persistent weakness down 60-80 cm remains sensitive to light triggers in isolated areas. Smaller avalanches have the potential to step down to this and deeper persistent weakness resulting very large avalanches.

Use conservative route selection, choose moderate angled and supported terrain with low consequence.Whumpfing, shooting cracks and recent avalanches are all strong indicators of unstable snowpack.Be aware of the potential for large avalanches due to the presence of deeply buried weak layers.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

3 - 4

Valid until: Feb 22nd, 2017 2:00PM