Archived

Avalanche Forecast

Dec 12th, 2014–Dec 13th, 2014

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

Alpine

2: Moderate

The avalanche danger rating in the alpine will be moderate

Treeline

1: Low

The avalanche danger rating at treeline will be low

Below Treeline

1: Low

The avalanche danger rating below treeline will be low

Regions: Purcells.

Although the trend shows improvement the potential for triggering an avalanche is greatest at higher elevations due to recent heavy snowfall and strong winds.

Confidence

Good

Weather Forecast

A ridge of high pressure will build over BC resulting in much drier and cooler weather for the next few days. Most areas should see a mix of sun and cloud with slight chance of the odd flurry. Freezing levels should gradually drop to 500-1000 m on Saturday and to valley bottom for Sunday and Monday. Winds ease off and become light and variable.

Avalanche Summary

Recent observations are limited from the region but there was a report of a size 2.5 explosive controlled wind slab on Thursday. This slide likely failed on weak layer buried in early December but appeared to step down to the early November crust. On Wednesday, one observer from the McMurdo Hut southwest of Golden reported seeing numerous avalanche crown lines and significant debris, particularly from alpine terrain. Natural activity should taper off this weekend but there may be lingering potential for triggering fresh wind or storm slabs higher in the alpine.

Snowpack Summary

The snow surface likely consists of moist/wet snow or a melt-freeze crust up to 2000-2200 m. Above this elevation there could be up to 40 cm of dense storm snow, which has probably been blasted around by strong southerly winds. In the Golden area a weak layer of surface hoar or facetted snow can be found under the storm snow. The mid pack consists of settled snow, facets, and melt-freeze crusts (primarily lower elevations). The mid-November weak layer (surface hoar, facets, and/or a crust) is buried 60-80 cm deep. Below this you will likely find a thick layer of sugary facets sitting on a solid rain crust from early November. The early November crust/facet layer did become reactive near Golden this week.

Avalanche Problems

Storm Slabs

Use caution in the alpine where most of the recent precipitation has fallen as snow. Watch for wind loaded or cross loaded slopes well below ridge crests from the past week of strong southerly winds.

Be aware of conditions that change with elevation and use ridges or ribs to avoid freshly wind loaded features.>

Aspects: All aspects.

Elevations: Alpine.

Likelihood: Possible

Expected Size: 1 - 4

Persistent Slabs

The likelihood of triggering a persistent slab should decrease heading into the weekend but be wary of any slope that did not release during the storms or has been reloaded.

Avoid common trigger zones including thin snowpack areas, near rocky outcrops, and steep alpine slopes.>Choose well supported terrain without convexities.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely - Possible

Expected Size: 2 - 5