Archived

Avalanche Forecast

Jan 2nd, 2017–Jan 3rd, 2017

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

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

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: Purcells.

Be extra cautious around south slopes: they're weak, wind-loaded, and getting hit by the sun.

Confidence

Moderate - Timing or intensity of solar radiation is uncertain

Weather Forecast

TUESDAY: Sunny with cloudy periods, light northeast winds, alpine temperatures around -22.WEDNESDAY: Mix of sun and cloud, light north winds, alpine temperatures around -18.THURSDAY: Mix of sun and cloud, light northwest winds, alpine temperatures around -18.

Avalanche Summary

On Sunday, isolated natural wind slab activity was reported on lee and cross loaded features in the size 1-2 range. Expect wind slabs to remain reactive to human triggers this week, especially on sun-exposed slopes. Also be aware that wind-loading and solar radiation may also make the persistent slab over the mid-December interface reactive in thin snowpack areas.

Snowpack Summary

Strong winds on Sunday had an extensive effect in exposed terrain at all elevations. Expect scouring, hard wind slabs, and thicker reactive wind slabs in unusual places as the winds shifted from west to northeast. Sunny weather is likely making the wind slabs extra touchy on south-facing slopes. The mid-December facet/surface hoar layer can be found buried 40-80 cm deep. This layer has shown signs of being poorly bonded to the overlying slab in snowpack tests, and has produced intermittent avalanche activity in shallow snowpack areas. The lower snowpack is well bonded and features a thick rain crust near the ground that appears to be dormant.

Avalanche Problems

Wind Slabs

Southerly aspects are wind loaded and becoming unstable with solar warming. Watch for wind slabs in unusual places, including open areas at lower elevations.

Avoid travelling in areas that have been reverse loaded by winds.Minimize exposure to steep, planar south facing alpine slopesIf triggered the wind slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 2

Persistent Slabs

Where denser snow overlies weak sugary snow, there is the potential to trigger large dangerous avalanches. Dig down and test for weak layers before committing to any steep slope.

Be aware of the potential for large avalanches due to the presence of buried weak layers.Avoid lingering in runout zones.Dig down to find and test weak layers before committing to a line.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Unlikely - Possible

Expected Size: 2 - 3