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Avalanche Forecast

Archived

Dec 20th, 2024–Dec 21st, 2024

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

Regions

Glacier.

The most recent storm snow still needs time to settle. Be especially cautious moving into steep wind effected terrain in the alpine.

Confidence

Moderate

Avalanche Summary

Several natural avalanches were observed in the highway corridor due to a wind spike overnight into Friday. Naturals ran up to size 3 with some running running full feature.

Avalanche control at Rogers Pass on Wednesday produced storm slab avalanches to size 3.

Snowpack Summary

15cm of new snow has fallen with strong gusting Southerly winds. This lands on a series of storm layers from the last week. A persistent weak layer is down 60-90cm. This interface consists of surface hoar in sheltered locations, a sun crust on solar aspects, and continues to produce moderate-hard sudden results in test profiles. The snowpack's base is comprised of several early-season melt-freeze rain crusts.

Weather Summary

Remnants of Saturdays coastal system will push into southern interior bringing a pattern of light snow & flurries overnight into the work week.

Tonight: Trace, Alp low -3°C, Mod-Strong SW wind, Freezing level (FZL) 1700m

Sat: 6cm. Alp High 1°C, Strong SW winds, FZL 1900m

Sun: Trace precip, Alp High -4°C, Moderate SW wind, FZL 1400m.

Mon: 4cm, Alp High -4°C, Moderate SW wind, FZL 1400m

Terrain and Travel Advice

  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.
  • Look for signs of instability: whumphing, hollow sounds, shooting cracks, and recent 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.