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Archived

Avalanche Forecast

Dec 29th, 2019–Dec 30th, 2019
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
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
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.

Although the likelihood of triggering large avalanches is decreasing, the persistent slab problem warrants avoiding steep convexities and areas with a shallow, rocky, or variable snowpack.

Confidence

Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.

Weather Forecast

Sunday night: Clear, light variable winds, alpine temperatures around -10 C.

Monday: Mostly clear, light southwest winds, alpine high temperatures around -3 C with freezing levels near 700 m.

Tuesday: Mostly cloudy, 5-10 cm of snow, moderate southwest winds, alpine high temperatures near -5 C with freezing levels around 700 m.

Wednesday: Mostly cloudy, 5-10 cm of snow, light to moderate west winds, alpine high temperatures near-3 C with freezing levels around 900 m. 

Avalanche Summary

Snowpack Summary

15-20 cm of new snow fell over the weekend on a weak interface. Forecast winds did not materialize to form reactive wind slabs except in isolated areas at upper elevations. 

Last week's storm deposited 70 to 100 cm of snow and a significant load to multiple weak layers. These layers include a feathery surface hoar layer (down 70 to 110 cm), an older surface hoar layer with a melt-freeze crust on steep south aspects (down 90 to 130 cm), and a layer of sugary faceted snow, surface hoar, and melt-freeze crusts from late November found in the bottom half of the snowpack. Snowpack tests continue to produce sudden results on these layers (check out this MIN report from Friday).

Although signs of instability are becoming less obvious, it remains prudent to make terrain decisions with the understanding that one or more of these deeply buried layers are present and could produce large and destructive avalanches with human triggers.

Terrain and Travel

  • Avoid shallow snowpack areas, rock outcroppings and steep convex terrain where triggering is most likely.
  • Persistent slabs have potential to pull back to lower angle terrain.
  • Uncertainty is best managed through conservative terrain choices at this time.

Avalanche Problems

Persistent Slabs

Several different deeply buried weak layers can be found in the snowpack that have produced large avalanches. These persistent slabs are gradually becoming less likely to trigger, but it remains prudent to assume these layers are present, reactive to human triggers, and capable of forming very large, destructive avalanches. 

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely - Possible

Expected Size: 2 - 3