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Avalanche Forecast

Archived

Nov 22nd, 2012–Nov 23rd, 2012

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

Regions

Glacier.

The winter permit system is not yet in effect but is scheduled to come into effect on Friday, November 23rd.  Click here for more information on how to obtain annual and daily winter permits.

Weather Forecast

Ridge of high pressure over the park will produce some clearing today. The ridge will break down later today as a warm front associated with a developing low pressure system moves over the area producing cloud and precipitation overnight and tomorrow

Snowpack Summary

Now over 90mm of load on the Nov 6 crust, down 60-100cm.  Whumphing, sudden collapse and sudden planar results have been reported on this layer recently. A cohesive storm slab has formed and appears to be reactive where it overlies the Nov 16 sun crust.

Avalanche Summary

2 size 2 natural observed above the highway corridor on the west side of the pass yesterday, limited visibility. 

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.

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.