Archived

Avalanche Forecast

Dec 1st, 2017–Dec 2nd, 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

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.

Lookout for fresh storm slabs reactive to human triggers in wind exposed terrain at treeline and above.

Confidence

Low - Due to the number of field observations

Weather Forecast

FRIDAY/NIGHT: 5-15 cm new snow expected by Saturday morning / Moderate to strong southwesterly ridgetop winds.SATURDAY: Mostly cloudy with isolated flurries / Light to moderate southwesterly ridgetop winds / Freezing level around 1000 m.SUNDAY: Mix of sun and cloud / Light northwesterly ridgetop winds / Freezing level valley bottom.MONDAY: Mix of sun and cloud / Light to moderate westerly ridgetop winds / Freezing level valley bottom.

Avalanche Summary

On Thursday, explosive control near Golden triggered several size 2 storm slabs ranging 15-45 cm deep. On Tuesday, in the Dogtooth range a skier was caught in a size 2 storm slab on a northwest facing slope at 2350m. The skier was uninjured in the avalanche which was about 40cm deep and 180m long.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, 20-60cm of snow has fallen at treeline and above with moderate to strong southwest winds, creating storm slabs sitting on a crust. Two other layers have been reported 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 have very little information on how reactive these layers are. In fact, we currently have very limited snowpack observations within this entire region and it is critical to supplement this information with your own observations.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.

Avalanche Problems

Storm Slabs

Recent wind and snowfall has likely formed reactive new storm slabs. Storm slabs may be more reactive in heavily wind-exposed terrain, or in areas where the new snow has a weak bond with underlying crusts.

The new snow may require several days to settle and stabilize.Watch for signs of instability such as whumpfing, cracking or recent natural avalanches.Be cautious as you transition into wind affected terrain.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 2