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Backcountry Advisory

As of Wednesday, June 9

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In the spring and summer, avalanche conditions are typically most stable in the morning, after a clear cool night which allows heat from the snowpack to escape into the atmosphere, resulting in the formation of a melt-freeze crust on the snow surface. This surface crust is what gives the snowpack its strength.

In its absence an isothermal snowpack is extremely unstable and unpredictable. Cloud cover and/or warm temperatures will inhibit the release of heat from the snowpack into the atmosphere and prevent the formation of surface crusts. In this scenario, the avalanche hazard may remain significant even early in the day. Exposure to the sun and warm temperatures will quickly break down any surface crusts, resulting in isothermal conditions and an increasing avalanche hazard. This transition will often happen very quickly.

Snowstorms can occur periodically throughout the summer months bringing significant snowfall accumulation to the alpine. Winter-like slab avalanche conditions can quickly return with the formation of windslabs overlying a smooth melt-freeze crust. These potentially unstable wind slabs are more of a factor during and immediately after storms when you can expect to encounter mid-winter avalanche conditions. This type of instability can accelerate rapidly as the storm-snow layers moisten and begin to sluff with exposure to the sun or with warming, after which returning to the classic melt-freeze cycle, or simply continuing to melt.

Route planning is often much more critical during this time of year than any other. Your timing in crossing some terrain features can be critical. Study the map closely and plan a route that takes exposure to the sun and daytime warming into consideration.

Have fun and travel safely. This advisory will not be updated until next mid-November.

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