Dashboard Regions Weather Stations Radar Alerts Glossary
Contact About
Log In

Register for an account and never miss a forecast again!

Register

Avalanche Forecast

Archived

Dec 24th, 2020–Dec 25th, 2020

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

Regions

Lizard-Flathead.

Recent wind loading may stiffen a thick slab that sits above buried, weak layers. This slab may be easily triggered by the weight of a person and initiate a large and destructive avalanche. A conservative mind-set is crucial with the current conditions. 

Confidence

Moderate - Uncertainty is due to how quickly the snowpack will recover and gain strength.

Weather Forecast

Friday: Mix of sun and cloud. Alpine temperatures near -3 and freezing levels 1100 m. Ridgetop wind moderate from the South.

Saturday: Chance of snow 5-10 cm. Alpine temperatures near -5 and freezing levels 1100 m. 

Sunday: Cloudy with isolated flurries. Alpine temperatures near -5 and freezing levels 1100 m and dropping to valley bottom overnight. 

Avalanche Summary

On Thursday a few explosive triggered size 1 avalanches were reported. 

On Wednesday numerous storm slabs up to size 1.5 were triggered with explosives. 

On Tuesday, a widespread natural avalanche cycle up to size 3 was reported from the lizard range. 

Natural avalanche activity may taper off a bit but the snowpack remains primed for human triggering. 

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

Snowpack Summary

30-50 cm of recent storm snow blanketed the region by Tuesday morning. Storm slabs will likely remain reactive to human triggers, especially where the wind stiffens the new snow. Deeper slabs will be found on lee slopes due to strong winds. 

A persistent slab 80-130 cm thick now sits on the early December crust. This persistent weak layer, with facetted crystals and surface hoar crystals above and/or below it is reaching a tipping point. 

Deeper in the snowpack are two hard melt-freeze crusts that formed in November that may have some weak crystals around them. This potential avalanche problem is dormant at this time, however; it remains on our radar.

Terrain and Travel

  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.
  • Shooting cracks, whumphs and recent avalanches are strong indicators of an unstable snowpack.
  • Don't let the desire for deep powder pull you into high consequence terrain.
  • Good day to make conservative terrain choices.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.