Avalanche Forecast South Rockies

Date Issued: Valid Until:

Avalanche Canada mconlan, Avalanche Canada

Avalanche Forecast

Sun Feb. 18th · 4:51PM

Alpine

Danger Ratings Considerable

Treeline

Danger Ratings Considerable

Below Treeline

Danger Ratings Considerable
Wind Slabs Wind Slabs
Cornices Cornices
Deep Persistent Slabs Deep Persistent Slabs

Alpine

Danger Ratings Considerable

Treeline

Danger Ratings Considerable

Below Treeline

Danger Ratings Moderate

Alpine

Danger Ratings Considerable

Treeline

Danger Ratings Considerable

Below Treeline

Danger Ratings Moderate
Recent snow and strong winds have produced touchy wind slabs. Watch for signs of avalanche activity and locally unstable snow, such as whumpfing and shooting cracks.

Confidence

Moderate - Due to the number of field observations

Weather Forecast

MONDAY: Partly cloudy, light northeasterly winds, alpine temperature -15 C, freezing level below valley bottom.TUESDAY: Mostly sunny, light westerly winds, alpine temperature near -12 C, freezing level below valley bottom.WEDNESDAY: Mostly sunny, moderate westerly winds, alpine temperature near -11 C, freezing level below valley bottom.

Avalanche Summary

On Saturday, small (size 1) loose dry and storm slabs were triggered naturally.Avalanche activity will continue as the recent snowfall begins to gain strength. Expect widespread loose dry and storm slab activity as well as wind slab activity in lee features. If triggered, these layers have the potential to release buried weak layers.

Snowpack Summary

Around 30-60 cm of storm snow with strong winds have created widespread loose dry and storm slab avalanche problems.  Some of this snow has been re-distributed with strong winds, creating wind slabs on lee features.  These slabs overly a layer of weak surface hoar buried mid-February that has produced very easy snowpack test results with sudden fracture characters.The lower snowpack in this region is weak with two main concerns:1)     a widespread weak layer from mid-December composed of facets, crusts, and surface hoar that is 100-150 cm deep.2)     a rain crust with sugary facets buried in late-November near the bottom of the snowpack. Although the snowpack structure is variable across the region, these persistent weak layers are generally widespread.

Problems

Wind Slabs

Wind Slabs

Recent storm snow fell with strong winds that have produced touchy wind slabs in lee features on all aspects. These slabs will likely be reactive to natural and human triggers. Be cautious of overhead exposure on solar aspects when the sun is out.

If triggered, the wind slabs may step down to deeper layers, resulting in large avalanchesA good day to be conservative, staying well away from overhead exposure.Choose shallow-angled and sheltered terrain where new snow hasn't been wind-affected.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 2.5
Cornices

Cornices

Cornices have grown in size with the recent storms.  If released, they could produce large avalanches that run far.

Avoid travelling below large corniced ridges.Remain well back from corniced ridges, giving them a wide berth.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 3.5
Deep Persistent Slabs

Deep Persistent Slabs

Several weak layers are lurking in our snowpack.  If triggered, they could propagate far, producing avalanches with high consequences.  Watch out for thin spots in the snowpack, where it is more likely to trigger them.

Be aware of the potential for wide propagation.Avalanches could run full-path: avoid runout zones of avalanche paths.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 4