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Avalanche Forecast

Archived

Dec 24th, 2022–Dec 25th, 2022

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

Regions

Glacier.

Before this storm, the snowpack was emaciated and weak - picture a stray kitten, out in the cold.

Now imagine this kitten sneaks into your house, and gorges itself on a turkey cooling on the counter - that's the state of our current snowpack.

Best to resist the urge to cuddle the little critter, or it might just throw up on you - avalanche terrain is like this kitten right now, give it some time.

Confidence

Moderate

Avalanche Summary

An avalanche cycle began Friday, and is ongoing at publishing time. Avalanche activity has been widespread, with our detection network signaling up to an avalanche per minute in the highway corridor at times. These avalanches have predominantly been in the size 2-3 range.

Snowpack Summary

Up to 45cm of new snow sits on a generally weak and facetted snowpack.

Prior to this storm the alpine snowpack was particularly thin and variable, with shallow areas facetted and unconsolidated from the snow surface to the ground.

There are several persistent weak layers buried, which are most prevalent at and near treeline. The recently buried Dec 16 surface hoar (up to 10mm) is now down ~50cm. The Dec 5 surface hoar layer is down ~70cm. The Nov. 17th surface hoar/suncrust/facet layer is down ~100cm and is the suspected failure plane for last weeks whumphing, as well as some large avalanches in neighboring areas.

Weather Summary

Sunday we will get a brief break between fronts. Scattered flurries will give up to 4cm, the alpine high will reach -4°C, and ridge wind will be light gusting moderate from the SW.

Monday will bring another wave of heavy snowfall. With up to 25cm forecast to fall throughout the day, high alpine winds, and freezing levels spiking to 1800m.

Tuesday will remain unsettled, with cloudy skies, scattered flurries and cooling temps.

Terrain and Travel Advice

  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.

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.