Avalanche Forecast

Issued: Jan 24th, 2020 4:00PM

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

ahanna, Avalanche Canada

South Rockies.

The MODERATE rating is not intended to be a green light for committing terrain. Natural avalanche activity has largely subsided though human triggered avalanches are still possible.

Summary

Confidence

Moderate - Confidence is due to a stable weather pattern; little change is expected for several days. Uncertainty is due to the fact that deep persistent slabs are particularly difficult to forecast.

Weather Forecast

Friday night: Up to 5 cm new snow. Moderate west to southwest winds. Freezing level down to 800 m.

Saturday: Mix of sun and cloud. Light west to southwest winds. Freezing level around 1500 m.

Sunday: Mix of sun and cloud with isolated flurries. Light southeast to southwest winds. Freezing level around 1500 m.

Monday: Mix of sun and cloud with isolated flurries. Moderate west to southwest winds. Freezing level around 1500 m.

Avalanche Summary

No new avalanche observations in the previous 4 days. On Monday we received reports of natural and explosive triggered wind slab avalanches size 1.5-2.

On January 16th, a natural size 2 wind slab stepped down to the deep persistent basal facets below a rock band, details here.

Snowpack Summary

Recent strong westerly winds have formed stiff wind slabs in exposed terrain at alpine and treeline. A crust can be found up to treeline and on solar aspects in the alpine due to recent daytime warming and sun exposure.

A well consolidated mid-snowpack overlies a generally weak basal snowpack. The bottom 10-20 cm of the snowpack consists of facets and deteriorating crusts. There is potential for this deep persistent layer to reawaken in the warm alpine temperatures this week.

Terrain and Travel

Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.

Problems

Wind Slabs

Strong southwesterly winds have blown recent snow into stiff wind slabs in lee features at alpine and treeline. Natural activity may have subsided but human triggering of wind slabs is possible.

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

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 2

Deep Persistent Slabs

We suspect that the warm temperatures are gradually helping the basal weak layers to bond, and the snowpack to strengthen. Deep persistent slab avalanches on these layers are unlikely but may still be triggered from shallow snowpack areas near rocky outcroppings.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely

Expected Size

2 - 3

Valid until: Jan 25th, 2020 5:00PM