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Archived

Avalanche Forecast

Dec 9th, 2019–Dec 10th, 2019
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
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
2: Moderate
The avalanche danger rating below treeline will be moderate
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
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: Glacier.

Weaknesses in the snowpack from late November may be difficult to trigger, but could produce very large avalanches. Conservative use of terrain is the best way to manage this problem.

Weather Forecast

A brief ridge gives cool and relatively stable weather for the next couple days. This will be followed by a pulse of precipitation mid week.

Today: Sunny periods. No precip. Treeline temps High -8 C. Light West winds.

Tonight: Mostly cloudy. TL temps Low -8 C. Light West winds.

Tuesday: Sunny periods. TL temps High -4 C. Light SW winds. Frzlvl 1300m.

Snowpack Summary

Moderate S-SW winds building fresh wind slabs in the alpine. 40cm of previous storm snow (since Dec. 5th) overlies surface hoar in some locations TL and BTL, and is concealing evidence of the recent cycle of natural avalanches. The November 23rd surface hoar/crust/facet layer is buried 80-100+cm and remains reactive in stability tests.

Avalanche Summary

Several large (up to size 2.5) natural avalanches were observed Saturday from steep terrain in the highway corridor.

Avalanche control Friday produced numerous size 3 and several size 3.5 avalanches.

Confidence

Due to the quality of field observations

Avalanche Problems

Persistent Slabs

The November 23rd layer is down 80-100+cm and consists of surface hoar at treeline and below, and a crust on steep solar aspects into the alpine.

  • Evaluate terrain features by digging and testing on adjacent, safe slopes.
  • Use conservative route selection, stick to moderate angled terrain with low consequence.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible

Expected Size: 1.5 - 3.5

Wind Slabs

Recent periods of moderate wind have potentially built wind slabs in immediate lees.  Keep an eye out for these as you transition into exposed alpine terrain.

  • If triggered the wind slabs may step down to deeper layers resulting in large avalanches.

Aspects: North, North East, East, North West.

Elevations: Alpine.

Likelihood: Possible

Expected Size: 1 - 2

Storm Slabs

40cm of recent storm snow has formed a slab. The new snow sits over Surface Hoar in some locations.

  • Dig down to find and test weak layers before committing to a line.
  • The new snow will require several days to settle and stabilize.

Aspects: All aspects.

Elevations: Treeline, Below Treeline.

Likelihood: Possible

Expected Size: 1 - 2.5