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Avalanche Forecast

Archived

Dec 11th, 2019–Dec 12th, 2019

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

Regions

Glacier.

Be aware of where other groups are traveling. Some unconventional up-tracks in the Rogers Pass area climb directly up the normal ski-line.

Reduce your exposure time by taking a safe route up.

Weather Forecast

Mainly cloudy today with flurries picking up in the afternoon, light SW winds at ridgetop, and alpine highs near -8*C. Wed night and Thursday will see a continuation of the flurries, amounting to ~10-15cm, with gusty, moderate SW winds and alpine highs around -5*C. Scattered flurries on Friday bring 5cm, light SW winds, and -7*C in the alpine.

Snowpack Summary

Moderate S-SW winds have created wind slabs in lee alpine features. Clear skies and cool temps have promoted faceting in the new snow, as well as surface hoar growth. The Dec 5 surface hoar is 30-40cm down and is stubborn in tests. The November 23rd surface hoar/crust/facet layer is buried 80-100+cm and is becoming stubborn in stability tests.

Avalanche Summary

Several natural avalanches, sz 2-2.5, were observed from both N and S aspects in steep, alpine start zones above the highway yesterday. No avalanche activity was noted from the backcountry yesterday. On Monday, human triggered avalanches to sz 2 were reported from steep, S-facing alpine start zones (Tupper and Ursus Major), failing on a crust.

Confidence

Problems

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.

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.