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Avalanche Forecast

Archived

Dec 18th, 2024–Dec 19th, 2024

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 unlikely, human triggered possible.

Regions

Glacier.

A significant storm brought 30cms of new snow with strong winds. Stick to conservative terrain while the new snow stabilizes.

Confidence

Moderate

Avalanche Summary

Avalanche control at Rogers Pass on Wednesday produced storm slab avalanches to size 3. Visibility was obscured and it was difficult to see the full extent of the avalanche cycle but some avalanches ran full path.

Snowpack Summary

30cm of new snow has fallen with strong gusting Southerly winds. This lands on variable wind slabs already present in the Alpine and at Treeline. A persistent weak layer is down 50-70cm. 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

In the wake of the storm we'll have unsettled weather with flurries for the next few days

Tonight Cloudy with flurries, Alp low -9°C, mod S winds, Freezing level (FZL) 800m

Thurs Cloudy with Snow flurries to 5cm, Alp high -4°C, mod S winds, FZL 1400m

Fri Mainly cloudy, flurries to 5cm. Alp high 1°C, light S winds, FZL 2200m

Sat Cloudy with flurries to 7cm, Alp high -3°C, mod/gusting extreme W winds, FZL 1900m.

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.