Archived

Avalanche Forecast

Jan 11th, 2019–Jan 12th, 2019

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

Alpine

4: High

The avalanche danger rating in the alpine will be high

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

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.

A big rise in freezing levels may mean that the deep persistent slab wakes up. A lot of uncertainty exists as to what this layer will do as temperatures climb. High levels of uncertainty are best managed by choosing conservative terrain.

Confidence

Moderate - Freezing levels are uncertain

Weather Forecast

Exact freezing levels and alpine temperatures are difficult to forecast in the coming days with mild temperatures and temperature inversions dominating the weather pattern this weekend.FRIDAY NIGHT - Cloudy with clear periods / southwest winds, 10-30 km/h / alpine low temperature near 0 / alpine temperature inversionSATURDAY - Cloudy with sunny periods / southwest winds, 10-30 km/h / alpine high temperature near +5 / Freezing level 1800 m / strong alpine temperature inversion with above freezing temperatures possible to 3000 mSUNDAY - Sunny with cloudy periods / southwest winds, 10-30 km/h / alpine high temperature near +7 / freezing level 3300 m MONDAY - Sunny / southwest winds, 20-40 km/h / alpine high temperature near +5 / freezing level 3000 m

Avalanche Summary

One size 2-2.5 natural avalanche was reported on a north aspect at 2200 m on Friday. This avalanche was likely triggered by a rock fall, and ran on the deep persistent layer at the base of the snowpack.A few size 1 natural and explosives triggered avalanches were reported in the region on Thursday.

Snowpack Summary

10-20 cm of recent storm snow has been redistributed by strong winds and has formed wind slabs at upper elevations. This new snow sits on previous hard wind slabs, a scoured and shallow snowpack on exposed ridges, and soft snow in sheltered areas. Large variability in snow depths still exists in the region, ranging from almost no snow to nearly 200 cm in some areas. For average snowpack areas, expect to find weak and sugary faceted snow around 50 to 100 cm deep, which extend to the ground. This weak bottom half of the snowpack has been the culprit for large avalanches in the region over the past few weeks. Warming temperatures and sunshine over the coming days could re-activate this layer, resulting in a possible avalanche cycle.

Avalanche Problems

Deep Persistent Slabs

Deeply buried weak layers remain a concern, especially as temperatures rise and the sun comes out. Large loads like cornices may trigger this layer as well, and cornice failures become more likely during warm, sunny conditions.

Use conservative route selection, choose moderate angled and supported terrain with low consequence.Pay attention to overhead hazards like cornices which could trigger the deep persistent slab.Watch for clues, like sluffing off of cliffs, that the snowpack is warming up.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible

Expected Size: 2 - 3

Storm Slabs

Slabs may become more reactive as temperatures rise and the sun comes out.

Be careful with wind loaded pockets, especially near ridge crests and roll-overs.Minimize exposure to steep slopes on warm or sunny days.If triggered the storm slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible - Likely

Expected Size: 1 - 2