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Archived

Avalanche Forecast

Dec 26th, 2022–Dec 27th, 2022
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
4: High
The avalanche danger rating at treeline will be high
Below Treeline
4: High
The avalanche danger rating below treeline will be high
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable

Regions: Glacier.

The new, heavy storm slab is overloading the weak, early-season facets, resulting in a natural avalanche cycle.

There will be significant whumpfing, settling, and remote triggering of avalanches over the next few days.

Stick to conservative terrain choices and manage your overhead hazards wisely!

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 and Boxing Day left deposits on the highway as well, with evidence of 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 60cm of new snow/storm slab sits on a generally weak and facetted snowpack.

There are several persistent weak layers buried, which are most prevalent at and near treeline. These layers can be found ~60cm (Dec 16 surface hoar), ~80cm (Dec 5 surface hoar), and ~100cm (Nov 17 surface hoar/suncrust/facets) below the surface. They are responsible for the significant whumphing under your feet, as well as the large avalanches above you in the mountains.

Weather Summary

Here it comes, more sloppy snow!! A warm Pacific front marches through our area, bringing high freezing levels (FZL), gusty winds, and moisture.

Tues: snow, 15cm, Alp high -1*C, moderate SW winds, 1800m FZL

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

Thurs: sunny periods, trace snow, Alp high -10*C, light winds, 500m FZL

Terrain and Travel Advice

  • Back off if you encounter whumpfing, hollow sounds, or shooting cracks.
  • 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.

Avalanche Problems

Storm Slabs

Heavy, warm storm slabs sit atop a weak, faceted early-winter snowpack. Hopefully they will flush out the unstable, sugary layers, but avoid avalanche terrain that has not been cleaned out by recent avalanche activity.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Very Likely

Expected Size: 1.5 - 3.5

Persistent Slabs

There are three persistent weak layers buried in the mid-upper snowpack. All three of these layers are still reacting in the easy/moderate range in snowpack tests around treeline.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible - Likely

Expected Size: 2 - 3.5