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Avalanche Forecast

Archived

Jan 29th, 2015–Jan 30th, 2015

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

Regions

Glacier.

Avalanche danger will increase with solar input this afternoon. Avoid exposure to overhead cornices that may trigger deep instabilities.

Weather Forecast

A ridge of high pressure will keep Rogers Pass dry today. A slight temperature inversion with light winds will trap clouds in the bottom of valleys, but the sun is expected to shine at higher elevations.  Temperatures return to winter norms with an alpine high of -5.  Light snowfall is expected for Friday afternoon as a frontal system moves inland.

Snowpack Summary

A breakable crust over moist to dry snow up to ~2400m. Above 2400m snow is heavily wind affected. The Jan15 surface hoar layer down 60-90cm is becoming more stubborn to trigger but is still likely to propagate. The Dec 17 surface hoar/ crust complex is down 130-180cm and is still reactive in snowpack tests. Large cornices have formed.

Avalanche Summary

No new natural avalanches were observed yesterday. An artillery verification shoot with 2 rounds produced a size 1.5 and a size 2 avalanche in previously controlled paths.

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.