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Avalanche Forecast

Dec 16th, 2019–Dec 17th, 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
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
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: Lizard-Flathead.

A stable weather pattern is forecast for the next few days with flurries at the end of the week.

Confidence

Moderate - Confidence is due to a stable weather pattern with little change expected.

Weather Forecast

Monday Night: Cloudy with clear periods and isolated flurries, trace to 5 cm. Alpine temperature -10 C. Southwest wind 25-45 km/hr.

Tuesday: Partly cloudy, partly sunny. Alpine temperature -6 C. Southwest wind 30-45 km/hr.

Wednesday: Mix of sun and cloud. Alpine temperature -6 C. Southwest wind 25-40 km/hr.

Thursday: Flurries, up to 10 cm. Alpine temperature -5. Southwest wind 15-35 km/hr.

Avalanche Summary

On Saturday, 2 large (size 2) natural storm slab avalanches were reported initiating from steep north-north east aspects in the alpine. Around Fernie, the new snow was reactive to skier tracks.

Avalanche activity late last week was primarily limited to small wind slab avalanches (size 1) triggered with explosives. On Thursday there was a report of a size 2.5 storm slab avalanche on a northeast aspect in the alpine, which scoured down to a crust near the base of the snowpack.

Snowpack Summary

Wind has redistributed loose snow, and formed wind slabs in exposed terrain and around ridge features. In sheltered areas 30-40 cm of snow from last weekend is gradually settling. 

Crust layers from November and October can be found 40-100 cm below the surface. These layers produced large avalanches with explosive triggers last weekend (Dec 13-14), but since then have appeared to gain strength. Large avalanches on these layers may still be possible to trigger in steep rocky terrain. 

Snowpack depths range between 50-130 cm at higher elevations and taper rapidly below treeline. Check out this MIN reporting conditions on Sunday at Harvey Pass.

Avalanche Problems

Wind Slabs

Triggering wind slab avalanches is most likely at higher elevations or cross-loaded areas where the wind has redistributed recent new snow into the lee of terrain features.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 2

Persistent Slabs

The likelihood of triggering a large avalanche on one of the crusts and weak layers in the lower snowpack is gradually reducing, but the consequence of doing so is high.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely

Expected Size: 1.5 - 2.5