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Avalanche Forecast

Archived

Nov 27th, 2015–Nov 28th, 2015

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

Regions

Glacier.

Sunshine and warm temps in the alpine are awfully tempting but keep in mind that the snowpack is going to undergo a rapid change in temperature. Expect avalanche danger to increase if temperatures rise above freezing, and with the strong solar.

Weather Forecast

Expect cold valley bottoms with valley cloud developing, but sunshine with a strong temperature inversion in the alpine. Above freezing temperatures are forecast above ~2000m. Light N'ly winds won't do much to help reduce the effect of warming. The high pressure system is expected to stick around until Monday or Tuesday.

Snowpack Summary

Recent strong northerly winds have reverse loaded southerly aspects creating wind slabs at ridgecrest. These slabs overlie a variety of surfaces, including suncrust on steep S-SW aspects, with 2-3mm surface hoar on most other aspects. Below this, the snowpack as a whole is strengthening. A weak basal layer exists on alpine N/NE aspects.

Avalanche Summary

Yesterday 6 size 2 avalanches were observed along the highway. They were likely triggered by the strong solar hitting the start zones. As the inversion develops over the weekend, we anticipate the recent storm snow may become increasingly reactive.

Confidence

Timing or intensity of solar radiation is uncertain

Problems

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.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.