Snowpack Summary for 12/5/2017

THIS SNOWPACK SUMMARY EXPIRED ON December 7, 2017 @ 2:25 pm
Snowpack Summary published on December 5, 2017 @ 2:25 pm
Issued by Aaron Hartz

bottom line:

Watch for signs of unstable wind slabs. Those signs include cracking in the snow and signs of rider or natural triggered slabs. During my tour yesterday at Ball Butte, the wind slabs were sticking well to the snow below them, however that might not be the case everywhere. Pay special attention to firm wind slabs that formed on top of the remnants of the soft snow that fell last week. If in doubt, avoid areas with wind affected snow on slopes steeper than 30 degrees.
As always, use normal precaution in the backcountry and carry your beacon, shovel, and probe.

Avalanche Character 1: Wind Slab
Wind Slab avalanches release naturally during wind events and can be triggered for up to a week after a wind event. They form in lee and cross-loaded terrain features. Avoid them by sticking to wind sheltered or wind scoured areas.
Snowpack Discussion

The storm that came in last week dropped around 25cm (10") on top of the solid Thanksgiving rain crust. As that storm came in, the new snow bonded well to the crust. Much of that storm snow was moved around by moderate northerly winds yesterday and putting an end to the powder skiing near tree line and above tree line.

We definitely have an early season snow pack. As of today, Mt. Bachelor is reporting 76cm (30") at their base. Recent backcountry observations report up to 125cm (49") at just under 8000ft. When the snow pack is shallow along with clear cold nights, faceting can occur in the snow pack and cause the snow to weaken. This could come into play especially on the shaded northern slopes that won't see much sun over the next week. It won't be much of a problem until more snow from future storms loads on top of the existing pack. This will be something to keep an eye on.

recent observations

We are light on recent observations. The COAA observer team is just getting ramped up for the season. We would like to encourage the public to submit snow and avalanche obs. Obs posts do not need to be overly technical, they can be as simple as writing something like..."we saw a skier triggered avalanche on ***aspect at ***elevation" ... or ... "we saw no human or natural triggered avalanches and found great riding conditions on *** aspects above tree line." If you have snow pit information that you want to share, feel free to post that also.


High pressure is the name of the game at least through early next week. We will have cold & clear nights in the mid to low 20's Fahrenheit and sunny warmer days with highs getting into the mid to upper 30's Fahrenheit. Wind is forecast to be light out of the east and south over the next few days.


This snowpack summary applies only to backcountry areas. Click here for a map of the area. This snowpack summary describes general avalanche conditions and local variations always occur. This snowpack summary expires in 48 hours unless otherwise noted.

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