Saturday, May 17, 2008

Snowpack goes Isothermal

It would appear we are in the midst of a large natural avalanche cycle. Due to extreme heat and deep weaknesses in the snowpack
Heavenly basin late Saturday afternoon let go significantly for
first time in 25 years

Blackcomb bowl

A mostly isothermal snowpack is being stressed by very warm temperatures. Little if any overnight crust recovery will alternate with very high freezing levels and may begining to stress deep istabilities in the snowpack. All these pictures are natural avalanche's. The December layer has awoken beware!
Lower Diesie ridge Saturday

A large natural cornice triggered size 2-3 avalanche off lower diesie ridge during the warming on the weekend. Possibly sliding on the Dec 3-4 rain layer. Temperatures yesterday reached +12.5 c at 2300m.

Also other reports of south facing slopes going isothermal and sliding to ground.

Cornice Impact zone

Flute slide

Brandywine area

From Canadian Avalanche Assoiciation

Warm Weekend Brings Avalanche Danger

May 14, 2008. The Canadian Avalanche Centre (CAC) is issuing a “heads
up” warning for anyone planning a mountain backcountry outing in Alberta or BC this coming weekend. The forecast dramatic rise in temperature, combined with the unusual
amount of snow that still remains in the mountains, may result in significant avalanche activity.

“We are well past our normal operating season and still talking about the danger of
avalanches,” says John Kelly, Operations Manager at the CAC. “This poses some big
problems for us at the avalanche centre because we have no current data about conditions,making it impossible to give specific targeted advice. However, we do know the basic ingredients are out there for a significant avalanche cycle.”

There are three key factors that make this situation unusual.
o This year’s snowpack is fundamentally unstable, with many deeply buried weak layers. In some areas the base of the snowpack remains extremely fragile, comprised of sugary snow with very little strength.
o A cold spring has kept the surface layers solid and strong, and preserved the weakness below. This creates prime conditions for slab avalanches, which are the most destructive type.
o The sudden hot weather we are expecting this weekend will melt the surface layers, and will trigger some large avalanches.

The CAC advises anyone travelling in avalanche terrain this weekend to leave a wide
margin of safety. Everyone in the party should be equipped with safety gear and be
familiar with how to use it.

Link to WB Avalanche Bullitin

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