Bob's Knob, Timpanogos Area, near Primrose Cirque. Sunny, warm, no wind. Felt like a hot spring day on the up track. Beautiful. Skied from abut 1:45 PM to 3:30 PM. Avalanche occurred at about 3 PM. 8700 feet. East/Northeast facing slope. 30-32 degrees. Soft slab on buried surface hoar (AGAIN). Broke about 100-150 feet wide, ran about 100-200 feet down the slope into small aspen trees. Unintentionally triggered by a splitboarder. No other cracking or instability observed. No wind. This is a fairly protected area. SW aspects had a sun crust, but the N/NE aspects were soft, and did not show evidence of heavy wind loading. 8-12 inches of really nice, medium density powder. Small surface hoar crystals were observed on the up track, could be next weeks problem layer. We skied a nearly identical slope to the one that fractured several times leading up to triggering this avalanche. I jumped on the top of these slopes in various spots, did a few ski cuts (this area makes high speed ski cuts off the ridgeline really easy) and pushed off some small cornices (lips really) trying to get any buried surface hoar to break out, but to no avail. On our final run we decided to ski a slightly different line, although very similar in aspect and slope angle to what we had spent the afternoon on. These two slopes are next to one another, separated by a small treed sub-ridge. I skied first, came to a stop half way down near some evergreens. Partner dropped in, but decided to cut across the slope nearer to my line when he triggered a very slow moving, shallow, but wide soft slab. He was able to stop and just watch as the slide run down the hill. Some observations: There were ski tracks on the slope, left early today I think, which I followed. It seemed that whoever left those tracks had a dog with them, and that dog more or less center-punched the slope, putting tracks down the very area that broke out. (Release the avalanche poodle?) The dogs tracks were covered by this avalanche, but the pooch somehow managed not to trigger the slab when he ran through. The weak spot appears to have been up a little higher. Plus a human is a lot heavier... There is one significant difference between the two slopes we skied today. The slope that fractured has a band of immature aspen trees running along the top, about 20 feet below the ridgeline. This further protects the area from wind that may have destroyed surface hoar on the other, successfully skied slope, and I think was one of the reasons the surface hoar persisted. The slab broke loose directly under these trees and propagated about 100-150 feet across. Because the slope angle was right around 30 degrees the slab ran very slowly, and not very far. It ran into more young aspens where it came to a stop. Only the new snow from yesterday's storm broke loose. It ran on what must have been more recent surface hoar crystals, rather than the other persistent, and now deeper layer that has been causing havoc. Incidentally, this is the same general area of the slides that Willie Holdman reported, although we did not see those. Forecasts have been accurate. We looked for the weak, persistent layers as we skied - as I mentioned, lots of ski cuts, jumping, hand pits and so forth. We found the weakness, but it still caught us a little off guard, given the skiing we had already done without it revealing its presence. It may have been tha the heat of the day had warmed the new snow enough to sufficiently overload the weak layer so that we made an easy trigger. It shows the pockety nature of this beast, and how fickle it can be. Comments Picture 1: Notice the band of aspens along the top of the slope. Splitboarder ready to enter the slope. Also notice the dog tracks running down the middle of the slope, and also mine from my last turn. Comments Picture 2: Splitboarder made his first turn, and his heading across the slope. Notice the lightening bolt crack below him, and also the fracture behind and above him. Comments Picture 3: More cracking below him, and the slope starting to move. I heard the slow whoosh of the slide before I actually saw the movement. Very cool, in an eery sort of way. Comments Picture 4: The avalanche in full run. Small blocks, shallow, slow moving. Very manageable, but still got our hearts pumping. Comments Picture 5: After the fact. My partner in the crown where he had stopped and watched. We both feel that had he made another turn into the slide (he saw the fracture and skied across and away from it) he would have been able to ski out from it safely, but his choice to cut across the slope ended up being a good one. This is an area that I have skied many times. It's a sort of "go to" spot when danger is high. Obviously this buried weak surface hoar does not care if I consider a particular slope "safe". The good news was the benign slope angle and the shallow nature of this slide meant we got a front row seat to another live demonstration of this persistent weakness. But still, not a show I want to see particularly often... or ever again for that matter.

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