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Avalanche Forecast

Archived

Dec 12th, 2020–Dec 13th, 2020

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Lizard-Flathead.

  

Northerly winds may form fresh wind slabs on generally windward aspects that may take riders by surprise this weekend. Use caution when transitioning into wind affected terrain.

Confidence

Moderate - Uncertainty is due to the limited number of field observations.

Weather Forecast

  

SATURDAY NIGHT: Partly cloudy / Strong, northwest ridgetop wind / alpine low temperature -14 / Freezing level valley bottom.

SUNDAY: Mostly cloudy / Strong, west ridgetop wind / alpine high temperature -10 / Freezing level valley bottom.

MONDAY: Mostly cloudy / Moderate, northwest ridgetop wind / alpine high temperature -9 / Freezing level valley bottom.

TUESDAY: Cloudy with flurries; 0-3 cm. / Strong, west ridgetop wind / alpine high temperature -7 / Freezing level valley bottom.

Avalanche Summary

No new avalanches were reported in this region on Friday.

On Wednesday, natural and human triggered avalanches were widespread and up to size 2 at treeline and above. Limited propagation was reported, however; these avalanches were running far and fast down the path as the new snow slid on the underlying crust.

Data in this region is very sparse. Please submit your observations to the Mountain Information Network. 

Snowpack Summary

Strong northerly winds continue to form wind slabs on lee features at tree line and above. Up to 30 cm of recent storm snow sits on top of a crust formed in early December. 

Deeper in the snowpack there are couple of crusts that formed in November. No recent avalanche activity has been reported on the November crusts.

Terrain and Travel

  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Closely monitor how the new snow is bonding to the crust.
  • Avoid areas where the snow feels stiff and/or slabby.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.