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Avalanche Forecast

Archived

Dec 25th, 2022–Dec 26th, 2022

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
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.

Here's another Xmas story...picture a large, grumpy elephant sitting on a child's tea-time table. That table is gonna burst!!

The snowpack is the tea table, the new storm snow is the elephant in the room. Natural and human-triggered avalanches are very likely.

Don't ruin tea-time today. Order a take-away bevy from the local ski hill where they'll tame the elephants as you have a lovely ski in-bounds! :)

Happy Holidays!

Confidence

Moderate

Avalanche Summary

A large natural avalanche cycle ripped through Rogers Pass Xmas Eve. Numerous avalanches from sz 2 to 3-3.5 were observed from Tupper, Macdonald, and other highway paths.

Artillery control on Xmas Day left deposits on the highway as well, with observations on Mac West Shoulder showing step-down avalanches on the persistent weak layers.

Avalanches have significant potential to increase in size once they gather up the lower elevation facets and persistent weak layers.

Snowpack Summary

Up to 55cm 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

Remember those gross, warm, wet Holiday kisses from distant relatives? The weather gods are in the spirit of giving, and they're set to smack us all over our cheeks Monday!

Monday: 20-25cm of snow, freezing levels (FZL) rising to 1900m, winds gusting 80km/h from the SW, Alp high 0*C

Tues: 10-15cm, 1600m FZL, light ridgetop winds gusting strong, Alp high -1*C

Wed: scattered flurries, 5cm, 1300m FZL, light winds, Alp high -4*C

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.