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Avalanche Forecast

Dec 18th, 2020–Dec 19th, 2020
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
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.

The recent snow has added load to buried weak layers and may still be reactive to human triggers, especially in wind loaded areas. Conservative terrain selection is recommended.

Confidence

Moderate - Uncertainty is due to the limited number of field observations. Forecast snowfall amounts are uncertain.

Weather Forecast

FRIDAY NIGHT - Mainly cloudy with flurries, 5-15 cm / southwest wind, 50-80 km/h, gusting to 100 km/h / alpine low temperature near -4 / freezing level 1100 m

SATURDAY - Mainly cloudy with scattered flurries, and 10-20 cm of snow on Saturday night / southwest wind, 40-80 km/h / alpine high temperature near -2 / freezing level 1500 m

SUNDAY - A mix of sun and cloud / southwest wind, 30-60 km/h / alpine high temperature near 0 / freezing level 2000 m

MONDAY - Flurries, 10-15 cm / southwest wind, 30-40 km/h gusting to 85 km/h / alpine high temperature near 0 / freezing level 2000 m 

Avalanche Summary

On Friday there were a few natural size 2 wind slab avalanches reported in the alpine.

On Thursday, a natural size 2 storm slab from NE alpine terrain was reported. As per the report, this slab likely failed on Wednesday. On Thursday, explosives were able to trigger slabs up to size 2 in the alpine and a size 1.5 at treeline.

Please consider sharing your observations on the Mountain Information Network. Thank you to those that have already submitted this winter!

Snowpack Summary

Strong wind from the southwest and up to 30 cm of recent fresh snow has likely formed reactive storm slabs. The recent storm snow accumulations mean that 40-60 cm now sits on the early December crust. This crust may have persistent weak, and facetted crystals above and below it. 

Deeper in the snowpack are two hard melt-freeze crusts that formed in November. The concern would be if there were weak faceted grains around the crust, but there is uncertainty if and where in the region this may be a problem. Without any recent avalanche activity, it appears that this layer is dormant for the time being.

Terrain and Travel

  • Avoid areas where the snow feels stiff and/or slabby.
  • Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
  • Choose relatively conservative lines and watch for clues of instability.

Avalanche Problems

Storm Slabs

The recent new storm snow has formed reactive storm slabs. Strong southwest wind is creating deeper slabs on leeward slopes that could produce larger avalanches. Loose-dry sluffing will likely occur from steep terrain features in sheltered areas.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely

Expected Size: 1 - 2

Persistent Slabs

40-60 cm of snow currently sits above a buried crust from early December. Sugary, facets above and/or below the crust may weaken the bond and the persistent slab may become reactive, especially to human triggers. 

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible

Expected Size: 1.5 - 2.5