Lizard Range and Flathead Avalanche Forecast

Issued: Dec 29th, 2020 4:00PM

Wed Dec 30th Current Conditions
Alpine Moderate Treeline Moderate Below Treeline Low
Thu Dec 31st 2 Day Outlook
Alpine Moderate Treeline Moderate Below Treeline Low
Fri Jan 1st 3 Day Outlook
Alpine Considerable Treeline Moderate Below Treeline Low

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is low. Known problems include Wind Slabs and Persistent Slabs.

Moderate hazard doesn't mean no hazard. Asses smaller slopes before committing to larger terrain. Avoid shallow rocky slopes and terrain where a small wind slab might have a large consequence.  

Summary

Confidence

High - Uncertainty is due to the speed, direction, or duration of the wind and its effect on the snowpack.

Weather Forecast

Tuesday night: Mainly cloudy, alpine low temperatures near -9C, freezing levels valley bottom & ridgetop winds moderate southwest.

Wednesday: Mix of sun and cloud with isolated flurries, trace-5cm new snow, alpine high temperatures -6C, freezing levels valley bottom & ridgetop winds moderate to strong southwest.

Thursday: Mix of sun and cloud with isolated flurries, trace-5cm new snow, alpine high temperatures -6C, freezing levels valley bottom & ridgetop winds light southwest.

Friday: Snow flurries, 5-10 cm new snow, alpine high temperatures -3C, freezing levels 1300m & ridgetop winds moderate gusting strong southwest.

Avalanche Summary

No new avalanches have been reported, except for sluffing of loose dry snow building mass to size 1 from steep wind sheltered terrain. In previous days, small wind slab avalanches were triggered with explosives, though they appeared to be more stubborn and isolated.  

Last week there was a significant avalanche cycle from heavy snow and strong winds. This cycle produced a few very large avalanches, including some that stepped down to deeper crusts and one that stepped down to the November crust in a nearby forecast region.  

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

Snowpack Summary

Recent winds have re-worked snowpacks in exposed ridgecrests and alpine areas leading to scouring, cross-loading and widespread wind slabs in lee features. Wind direction has been variable, but largely from the southwest loading north and east aspects.

Below 1800m, 15-25 cm of snow sits atop a buried melt-freeze crust. Buried deeper are few weak layers of interest. Buried 40-90 cm is a layer of surface hoar crystals and a crust from early December with facetted crystals. These layers are showing signs of slowly gaining strength, but remains layers of concern. This MIN from the 27th near Mongolia Bowl reports a notable weak layer down 40cm.  

The base of the snowpack consists of a hard melt-freeze crust / sugary facets from early-November. This potential avalanche problem remains on our radar.   

Terrain and Travel

  • Pay attention to the wind, once it starts to blow fresh sensitive wind slabs are likely to form.
  • Watch for areas of hard wind slab on alpine features.
  • Approach lee and cross-loaded slopes with caution.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
  • Avoid shallow snowpack areas, rock outcroppings and steep convex terrain where triggering is most likely.

Problems

Wind Slabs

An icon showing Wind Slabs

Likelihood

Possible

Expected Size

1 - 2

Be on the lookout for wind-loading in lee north and east slopes from southwest winds. Older buried windslabs and cross-loaded features on all aspects are also suspect.    

Aspects:

North, North East, East, South East, North West.

Elevations:

All elevations.

Persistent Slabs

An icon showing Persistent Slabs

Likelihood

Unlikely-Possible

Expected Size

1.5 - 3

Depending on elevation and aspect, 40-150 cm of snow currently sits above buried weak layers from early December. Buried surface hoar and sugary facets around the crust mean persistent slabs remain on our radar and may be triggered with large triggers or in a shallow snowpack.  

Aspects:

All aspects.

Elevations:

Alpine, Treeline.

Valid until: Dec 30th, 2020 4:00PM