Archived

Avalanche Forecast

Feb 1st, 2019–Feb 2nd, 2019

Alpine

4: High

The avalanche danger rating in the alpine will be high

Treeline

4: High

The avalanche danger rating at treeline will be high

Below Treeline

4: High

The avalanche danger rating below treeline will be high

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

Treeline

3: Considerable

The avalanche danger rating at treeline will be considerable

Below Treeline

3: Considerable

The avalanche danger rating below treeline will be considerable

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

Treeline

3: Considerable

The avalanche danger rating at treeline will be considerable

Below Treeline

2: Moderate

The avalanche danger rating below treeline will be moderate

Regions: South Rockies.

Precipitation amounts overnight Friday are higher than what was forecast with some areas in the region (particularly along the divide) receiving 30cm + snow. In light of this avalanche danger is RATED as high. Updated Feb 2, 2019.

Confidence

Moderate -

Weather Forecast

FRIDAY Night: Cloudy with light snowfall, accumulation 5-30 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

The likelihood of triggering avalanches will increase with new snow and wind. 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.

Avalanche 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.

Be careful with wind-loaded pockets, especially near ridge crests and roll-overs.Be cautious as you transition into wind affected terrain.

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

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 1 - 1.5

Persistent Slabs

Around 20 to 40 cm of snow sits above a weak layer of feathery surface hoar crystals, which is best preserved in shaded and sheltered areas between 1500 m and 1900 m. On southerly aspects, the snow sits on a hard melt-freeze crust.

Be very cautious in open terrain features, such as cutblocks, gullies, and cutbanks.If triggered, slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Treeline, Below Treeline.

Likelihood: Possible

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.

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

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Unlikely - Possible

Expected Size: 2 - 3