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Archived

Avalanche Forecast

Jan 20th, 2013–Jan 21st, 2013
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
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
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
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: Kootenay Boundary.

Confidence

Fair - Timing, track, or intensity of incoming weather is uncertain on Wednesday

Weather Forecast

Monday: Inversion. Freezing level at surface. Above freezing layer from 1500m – 2500m. Ridgetop winds Mod NW. Treeline winds light W. No precip. Scattered cloud, clearing in the afternoon.Tuesday: Should be the last inverted day. Freezing level at surface. Above freezing layer from 1500m – 3000m. Ridgetop winds Mod W. Treeline winds light SW. No precip.  Broken cloud cover for most of the day.Wednesday: Freezing level at valley bottom. Snow beginning Tuesday night, carrying into Wednesday.  I expect around 5 cm by Wednesday morning with an additional 5 – 10 during the day Wednesday.  Ridgetop winds initially light SW, steadily increasing to strong NW by late afternoon.

Avalanche Summary

No new natural activity. On Saturday a size 2 avalanche was spotted that was suspected to be sled triggered.  It was just below ridgetop on an east aspect at 2200m.  On Friday a group of skiers triggered a small (size 1.5) hard slab avalanche the failed when the 3rd skier traversed across an east facing slope at 2000m.

Snowpack Summary

Savage winds out of the NW have wreaked havoc on the region. N & W facing slopes are wind pressed or wind-stripped. Slopes lee to these winds were left with wind slabs up to a meter in depth in open areas. While the results of the recent winds appear dramatic, the wind slabs are quite stubborn in their trigger-ability for the most part.  There are of course, exceptions, see the recent avalanche observations. Warm temperatures have created moist snow that can be found on almost all aspects up to 2300m. Protected areas are growing surface hoar to 20mm, while many other slopes are sporting a zipper crust due to the warm temps. Under the snow surface lies the January 4th interface, down around 75 cm & obviously much deeper in wind loaded areas. This layer of small/facets/crusts and intermittent surface hoar is producing planar shears in some drainages and no failure at all in others. At the moment it's tough to find soft snow to recreate in. The midpack is well good, nicely bonded and strong.

Avalanche Problems

Wind Slabs

Previous extreme winds out of the W/NW left hard slabs, soft slabs, sastrugi and potentially unstable cornices in their wake. Many of these slabs have grown old and tired, but the odd sensitive slab may still be lurking out there.
Be cautious as you transition into wind affected terrain.>

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

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 4

Persistent Slabs

While unlikely, it may still be possible to trigger this layer on the odd slope.  I'm thinking about a steep rocky slope with a snowpack thinner than the regional average.  Sensitivity may increase slightly Monday with warm temps and direct sun.
Watch for glide cracks and give these unpredictable natural phenomena a wide berth.>Low danger doesn't mean no danger. Be cautious around steep sun exposed slopes Monday afternoon.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Unlikely

Expected Size: 1 - 5