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Avalanche Forecast

Dec 18th, 2019–Dec 19th, 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
4: High
The avalanche danger rating in the alpine will be high
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable
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
3: Considerable
The avalanche danger rating below treeline will be considerable

Regions: Lizard-Flathead.

Triggering an avalanche is most likely in wind affected terrain and steep, rocky slopes.

Confidence

Moderate - Uncertainty is due to the timing of the incoming weather system.

Weather Forecast

Wednesday Night: Mostly cloudy. Alpine temperature -8 C. Southwest wind 25-35 km/hr.

Thursday: Cloudy with isolated flurries, trace to 10 cm. Alpine temperature -5 C. Southwest wind 25-45 km/hr.

Friday: Snow, 20-40 cm. Alpine temperature -1 C. Southwest wind 20-40 gusting to 65 km/hr. Freezing level rising to 1900 m.

Saturday: Continued flurries, 5-15 cm. Alpine temperature -2 C. Southwest wind 35 gusting to 75 km/hr. Freezing level 1600 m.

Avalanche Summary

Two natural wind slab avalanches were reported Wednesday morning, these avalanches were suspected to have failed overnight as strong winds reached 90 km/hr.

Explosives testing was able to trigger a handful of small (size 1) slab avalanches on Tuesday from steep alpine terrain.

Snowpack Summary

Wind has redistributed loose snow, and formed wind slabs in alpine terrain and around ridge features. In sheltered areas 20-40 cm of loose snow 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 around 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 60-120 cm at higher elevations and taper rapidly below treeline. 

Avalanche Problems

Wind Slabs

Triggering wind slab avalanches is most likely at higher elevations or cross-loaded areas where the wind has redistributed loose snow. Use extra caution with strong and gusty winds - touchy new slabs have formed in exposed terrain and ridge features.

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

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 1.5

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