From NWAC - This is worth noting

The front late Sunday was accompanied by warming with heavy precipitation rates, being repeated Monday as well along with very strong winds. These storms caused rapid loading and produced widespread natural avalanches in many areas including some very large avalanche releases. A park ranger at Hurricane Ridge Tuesday morning reported that the "Old Faithful" slide path released sometime overnight depositing up to 8 feet of avalanche debris across the road, the largest release recently. Many other slides have been reported in the Cascades including Crystal Mountain valley late Sunday (Ted's Buttress 6-8 ft crown), on Shuksan arm midday Monday (BIG! larger than 1999).

Some of these slides may have released to older crust-facet layers from mid to late February, with many other slides releasing in storm layers.


The 1999 Shuksan Arm slide had a 15' crown, so this is a monster. You would need a shovel with a long handle to check that one out!  It will be interesting to travel through the Cascades this spring and summer and observe some of this evidence. The problem should die down the next few days west of the crest but on the eastside it is still a possibility. This layer will undoubtedly make a comeback for huge natural slides in mid-spring or so. To get a feel for the east side situation, some of the CAA bulletins provide a glimpse at snowpacks that may be related since NWAC has limited observations along the east side..

The crown in this Shuksan Arm avalanche was 15' (the 1999 slide was 12-15'). The debris completely filled Rumble Gully and was more substantial than in 1999. The ski patrol had done control work the preceding day with significant results which partially filled the gully. This avalanche released as a natural at 10:00 am Monday. The ski patrol amazingly counted 40 tracks going into Rumble Gully despite the obvious avalanche hazard!

The 1999 avalanche killed (was it 2 or 3 people?). It may have been human triggered. In any case people were on it when it went. Apparently there was a traverse track that was heavily used that cut across the base of a steep convexity in the earlier event. It was conjectured at the time that by traversing the slope skiers had removed strength from supportive near surface layers which in turn may have caused redistribution of stress in the slab. It is ordinarily thought that it is difficult to trigger slides deeper than 3-4' unless they step down to overload deeper weaknesses. In my experience I have triggered a 4' slab.

Ted's buttress is the steepening part of the south ridge of East Peak. The slide was on the risky, almost always wind loaded terrain on the northern slope of that feature.

Thanks for these updates Gary -- sobering stuff.

NWAC must just save the black and red rosettas for the days they believe the slides will close the interstate highways.

Wow that is huge indeed. The only time I've seen the extreme hazard from NWAC is usually during a rainy, warm event immediately following a large snowfall, usually with some buried unstable layer for good measure.

Ted's buttress is the steepening part of the south ridge of East Peak. The slide was on the risky, almost always wind loaded terrain on the northern slope of that feature. 

Interesting. I wonder where this slide is in relation to the avalanche path mentioned in this thread (near the old Bullion Basin runs):

www.turns-all-year.com/skiing_snowboardi...76.msg80080#msg80080

www.turns-all-year.com/skiing_snowboardi...76.msg80142#msg80142