Avalanche Forecast

Issued: Feb 1st, 2019 5:25PM

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

mbender, Avalanche Canada

South Rockies.

Some new snow combined with forecast moderate to strong winds will promote wind slab development.

Summary

Confidence

Moderate - Due to the number of field observations

Weather Forecast

FRIDAY Night: Cloudy with light snowfall, accumulation 5-10 cm, moderate to strong southwest winds, alpine temperature -5 C, freezing level 1400 m.SATURDAY: Cloudy with flurries, accumulation 5 cm, light to moderate southwest winds, alpine temperature -5 C, freezing level 1300 m.SUNDAY: Cloudy with isolated flurries, light east winds, alpine temperature -24 C.MONDAY: Mix of sun and cloud, light east wind, alpine temperature -20.

Avalanche Summary

On Wednesday, a skier triggered a small slab at treeline on a west to northwesterly aspect. On Tuesday, a small avalanche triggered by a snowmobile was observed, releasing on the surface hoar layer described in the Snowpack Summary. Shooting cracks were also observed, suggesting instability with that layer.

Snowpack Summary

New snow Friday evening will continue to build a slab over a weak layer of feathery surface hoar crystals, which is suspected to buried about 10 to 30 cm. The surface hoar is most prominent between 1500 and 1900 m but has been found up to 2100 m. On south aspects, the snow overlies a melt-freeze crust to the top of the mountains.The middle of the snowpack is generally consolidated. The bottom half of the snowpack is unconsolidated and composed of weak and sugary faceted grains.

Problems

Wind Slabs

Some new snow combined with moderate to strong southwest winds will have created wind slabs in the lee of terrain features at upper elevations.

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

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 1.5

Deep Persistent Slabs

The bottom of the snowpack consists of weak and sugary faceted snow. There is a relatively low likelihood of triggering this layer at the moment, but the consequences remain high, as avalanches on this layer will be large and destructive.

Use conservative route selection, such as moderate-angled and smooth terrain with low consequence.Watch for signs of instability such as whumpfing, cracking, or recent avalanches.Avoid steep, rocky terrain and shallow snowpack areas where triggering deep layers is more likely.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

Valid until: Feb 2nd, 2019 2:00PM