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Avalanche Forecast

Archived

Dec 28th, 2022–Dec 29th, 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 avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
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 possible, human triggered probable.

Regions

Glacier.

A reactive storm slab is present throughout the park. This is sitting on a weak base of sugary crystals.

There may be some significant settlement of the snowpack in the coming days, with whumpfing and shooting cracks alerting you to dangerous conditions.

Confidence

Moderate

Avalanche Summary

Natural avalanche activity has reduced with the decreased snowfall/winds.

A field team triggered a size 1 avalanche on a steep feature at tree-line. The avalanche failed down 10-15cm in the storm snow.

Artillery control on Xmas and Boxing Day had good results, with many avalanches observed in the sz 2.5-3.5 range. There was evidence of step-down avalanches on the persistent weak layers.

Be suspicious of slopes that do not appear to have avalanched in the last few days.

Snowpack Summary

South/westerly winds in the moderate range on Thursday will redistribute the recent storm snow.

A warm storm slab 55-65cm deep sits on top of weak cold, loose faceted snow. This interface is reactive in the easy to moderate range of snowpack tests, while the persistent weak layers (PWLs) below were stubborn in tests Tuesday at Fidelity.

The reaction of the PWLs to the overlying burden is the thing to watch the next few days. Dig down and test them.

Weather Summary

Temperatures will be seasonal norms as light snow continues through Saturday.

Thurs: Cloudy w/Sunny periods, isolated flurries w/trace snow, Alp high -8*C, Wind SW-25 km/h, 700m FZL

Fri: Mainly cloudy w/scattered flurries, 4cm of snow, Alp high -6*C, Wind SW 20-35 km/h, 1200m FZL

Sat: Mainly cloudy w/scattered flurries w/trace snow, Alp low -7*C, Wind SW 20-35 km/h winds, 1100m 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.

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.