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Avalanche Forecast

Nov 27th, 2017–Nov 28th, 2017
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
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: Purcells.

New snow and southerly winds will be driving avalanche danger on Tuesday. Avoid exposure to avalanche terrain during periods of rapid loading by rain, snow, or wind.

Confidence

Low - Due to the number of field observations

Weather Forecast

The next system arrives on Tuesday with modest amounts of snow and more seasonal freezing levels. TUESDAY: Snow (5-15cm) during the day with another 5-10cm possible overnight. Moderate southerly ridgetop winds. Freezing level around 1000 m.WEDNESDAY: Clearing throughout the day. Moderate westerly ridgetop winds. Freezing level around 1200 m. THURSDAY: Cloudy with isolated flurries. Light to moderate southwesterly ridgetop winds. Freezing level around 1100 m.

Avalanche Summary

On Monday, a Size 2 wind slab was reported with explosives control work in the north of the region on a northerly aspect near 2300m. Natural avalanche activity is expected on Tuesday with another pulse of snow. We currently have very limited observations in this region. Please submit your observations to the Mountain Information Network (MIN).

Snowpack Summary

Last week, the November 23rd crust formed as temperatures cooled and the rain-soaked snow surface froze. Since then, 15-40cm of snow has fallen at treeline and above with moderate to strong south (west) winds, creating wind slabs sitting on a crust. The depth of the snowpack varies greatly with elevation. Recent reports suggest the average depth is 150+cm in the alpine, 100-150cm at treeline, and decreasing rapidly below treeline where the primary hazards are rocks, stumps, and open creeks. There are two other layers of concern in the snowpack: 1) The Halloween crust (down 100cm at treeline elevations) and 2) The November 10th surface hoar / facets (down 80cm at treeline elevations).We currently have very limited snowpack observations within this region and it is critical to supplement this information with your own observations.

Avalanche Problems

Storm Slabs

A natural avalanche cycle is expected on Tuesday with the incoming snow.
Use conservative route selection, choose moderate angled and supported terrain with low consequence.Watch for signs of instability such as whumpfing, cracking or recent natural avalanches.Avoid exposure to avalanche terrain during periods of rapid loading by snow or wind.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 1 - 3

Persistent Slabs

Rapid loading by rain or snow will increase the likelihood of avalanches occurring on this layer.
Avoid exposure to avalanche terrain during periods of rapid loading by rain, snow, or wind.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 2 - 3