Archived

Avalanche Forecast

Feb 16th, 2017–Feb 17th, 2017

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

Treeline

2: Moderate

The avalanche danger rating at treeline will be moderate

Below Treeline

1: Low

The avalanche danger rating below treeline will be low

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

Treeline

2: Moderate

The avalanche danger rating at treeline will be moderate

Below Treeline

1: Low

The avalanche danger rating below treeline will be low

Alpine

2: Moderate

The avalanche danger rating in the alpine will be moderate

Treeline

2: Moderate

The avalanche danger rating at treeline will be moderate

Below Treeline

1: Low

The avalanche danger rating below treeline will be low

Regions: South Rockies.

New snow and rain has created touchy snowpack conditions. Give the snow time to settle before pushing into bigger terrain.

Confidence

Moderate - Freezing levels are uncertain

Weather Forecast

THURSDAY NIGHT: Another 5 cm of new snow with greater accumulations to the south as a cold front passes through. Strong southwest winds and freezing level dropping to 1500 m.FRIDAY: Cloudy with sunny periods, moderate southwest winds, freezing level around 1500 m.SATURDAY: Cloudy with light flurries starting in the afternoon, light to moderate winds, freezing level around 1300 m.SUNDAY: Cloudy, moderate southwest winds, freezing level around 1500 m.

Avalanche Summary

Recent observations have been limited; however, a few size 2 solar-triggered persistent slab avalanches were observed in the Elkford area on Tuesday. They were thought to be about a day old and appeared to have failed on the December facets. Gradual cooling should help to limit natural avalanche activity at this interface. However, the December facet layer will be with us for a while and should not be trusted as we enter a low-probability/ high consequence pattern with this layer. Wind slabs will also remain reactive to human triggers at higher elevations.

Snowpack Summary

The region received 5-15 mm of precipitation on Thursday, which fell as rain in the valleys and as snow above 1800 m. Moderate to strong southwest winds are shifting these accumulations into reactive wind slabs in exposed high elevation terrain. Beneath the new snow, you'll find a mix of hard old wind slabs, melt-freeze crusts, and moist snow from the recent warm spell. Some weaknesses may still exist within the 90 cm of storm snow from last week; however, recent warming has likely helped to strengthen these layers. In deeper areas, the mid and lower snowpack appear to be well settled with only isolated concerns about the mid-December facet layer which comprises the bottom third of the snowpack. In shallow snowpack areas, this layer is weak, faceted, and has no structure. In these areas, snowpack test results and reports of whumpfing suggest large avalanches remain a concern at this interface. Watch this video from the South Rockies field team for some recent results on deeper facet layers.

Avalanche Problems

Deep Persistent Slabs

A weak layer at the base of the snowpack has the potential for climax avalanches. As temperatures cool over the next few days, this weakness may gain strength. I still don't trust this layer, especially in areas with minimal rider compaction.

Be aware of thin areas that may propogate to deeper instabilites.Avoid steep convexities or areas with a thin or variable snowpack.Be aware of the potential for full depth avalanches due to weak layers at the base of the snowpack.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 2 - 3

Wind Slabs

Watch for fresh and reactive wind slabs in exposed high elevation terrain.

Use ridges or ribs to avoid pockets of wind loaded snow.Be cautious as you transition into wind affected terrain.

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

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 2