** IMPORTANT ANNOUNCEMENT **

As of March 30th, COAC has suspended backcountry avalanche advisories and pro observations until further notice.

On March 23rd, Governor Brown of Oregon issued Stay at Home orders for the public regarding the COVID-19 outbreak. The directives are clear in that “to the maximum extent possible, individuals stay at home or in their place of residence.” On March 27th the Deschutes National Forest issued a closure of all developed recreation sites including trailheads and snoparks. COAC is committed to supporting our community, local emergency services, and agency partners and because of this we felt it important to cease operations as we all work together to minimize the impacts and spread of COVID-19.   

This decision was not taken lightly. Aside from the need to maintain congruency with the Governors' orders, there are inherent risks with backcountry activities in alpine environments and it’s important to consider unnecessary exposure to COAC forecasters, first responders, and local medical staff in light of the current situation.

We look forward to getting back into the mountains and providing you all with the tools to recreate safely in the backcountry. Until then we thank you for your continued support and wish all our mountain community the best of health and wellness.

Tam - Natural and Skier Triggered Slides

Location Name
Tam MacAurthur Rim
Region
Three Sisters Area
Name
John Stevenson
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I would like this observation to be published on the site
Position
Public
Date and time of avalanche (best estimate if unknown)
Red Flags
Recent avalanche activity
Recent loading by new snow, wind, or rain
Rapid warming
Obvious avalanche path
Avalanche Type
Slab
Blowing Snow
Yes
Trigger type
Other-please explain in the comments
Wind Speed
Moderate
Slope
35degrees
Wind Direction
Southwest
Air temperature
Below Freezing
Aspect
Northwest
Air temperature trend
Warming
Elevation
7000ft.
Bed Surface
Old Snow
Cloud Cover
100% of the sky covered by clouds
Precipitation
Snow
Weak Layer
Storm Snow
Crown Height
2 ft
Accumulation rate
<1
Avalanche Width
30ft.
Avalanche Length
300ft.
Terrain
Near Treeline
More detailed information about the weather

 ~20-30 new snow last 48-72 hours with period of rain forcasted to hit early previous evening before tranisiting back to snow in the AM.  Strong SW winds

Number of similar avalanches
1
More detailed information about the avalanche

Skied at Tam MacAuthur Rim on Sat (3/29) but called it after one lap based on avy observations.  Our pit work showed weaknesses (CT11-24) with decent shear quality (Q1+ to Q2-) at a couple of places in a very wet/heavy storm slab and at its interface to the pre-storm snowpack about 2 ft down - but no full propagation on our ECT.Our plan was to work our way up on conservative terrain and put in another pit, but soon came across a fresh crown ~ 30 feet across, maybe 1-2 ft thick.  It propagated on rocks in an open patch of trees but ran well through them to a bench ~ 100 yards below.  All of this was at the base of the cliffs S/SE of the 3 Sisters Huts,  7000ftFor obvious reasons we didn't get close enough to investigate very well.   From where we stood there was no evidence of ski tracks entering or exiting suggesting it was naturally triggered.  It also looked like there was 1-2'' of new snow on top of the debris so it likely released sometime that morning or night before, possibly from the rain that had been forecasted to hit that night.About that same time another ski party came by and reported setting off a similar sized slide/depth close by which made the decision to bail all the more conclusive.