Avalanche Discussion

Tumalo Mt. near Mt Bachelor......Friday I witnessed two "no-brainer" new snow/ wind slab slides. Lots of new snow plus high winds ( and so, wind transport... ) yielded loading in the usual suspect areas-- a cornice of 40ish degrees starting zone directly tucked underneath-- and the other on another similarly in degrees steep starting zone (this one has pretty much turned into a "burnished" surface as it releases snow quitie regularly when ever the big dumps arrive)

The slab from under the cornice event occur when one skier hopped off the cornice and stopped in the middle of the slope to see his buddy do the same. The first guy got to see the whole slope expode as his buddy maytaged his way down to near the first guy (who also got hit by the slide...)...Fortuntely both stayed on top (and seemed to not be hurt) and were able to find all there belongings and able to ski to safety. Looked like no awareness of snow stability/ mechanics nor terrain managment protocal. Once again, the clueless servived (or what I percieved to be "clueless".

Lots of windslab near crystal in the bc on Friday as well. No releases, but once the sun was out and shining brightly, we also experienced a lot of whumfing and vacated the area (Cement Basin). The settling occured in mostly safe terrain, but the warning signs were apparent and we took note and played it safe moving to other aspects that weren't sun affected.

A word of warning. Test for this layer near Stevens Pass:

Interesting layer found between about 4800' and 5300' on NW through NE aspects. The layer of graupel about 1-1/2" thick and overlying firmer snow is now buried about 24". This layer was responsible for a remarkable number of dry slabs recently. I do not know the age of the layer but find that 10-12" of snow has accumulated since the avalanche cycle. The number of slabs observed was somewhere between a dozen and 2 dozen on angles of 35 degrees and up in mostly gladed terrain. One slab propagated across the head of three small scale gullies typical of the Heather Ridge terrain. Additional slopes were cracked but hadn't released. Ski tests on a couple of the few safe slopes that hadn't slid were unremarkable at about 5300' but additional ski tests and skiing on steep terrain below about 4800' showed good stability. But that may be because the graupel was (or has been moist below that elevation at some point in time. A snowpit at 5100' yielded an easy to moderate shear at 24" and a compression test score of 19 was obtained. But since the overlying layers are just fist and 4F hard the CT result may overstate the stability of the layer. This layer doesn't lend itself to discovery by pole testing and "feel" of the skis. The upper limit of recent slab observations are probably just because of the terrain limitations at Heather Ridge and the weak layer should extend higher. I would be concerned about this layer on steep rolls (where most releases were) on north aspects near Stevens Pass. On sunnier aspects where a buried suncrust underlies recent snows it seems likely that the formation of the suncrust has mitigated this weakness. Those slopes felt stable while dry today.

I've only seen surface hoar act as unstable as this graupel layer has recently shown itself to be and the terrain where the slabs occurred has rarely had more than an occasional slab historically.