From NWAC - This is worth noting

Agreed X2!!

All of Gary's response are biblical to my concerns and good reminders too.
Those who are newer (even less aware experienced folks) who have taken avy 1 or 2 classes can't hang their hats on those classes. Just like a shovel, they are just tools.
The real tool is the awareness of the experiences and a growing inventory of experience comes from return trips. It would be a heuristic trap for me to think that my 35 years of BC touring makes me an expert. I just have the privilege of seeing a lot more things over and over to base some conclusions, but mistakes will happen. It comes down to a numbers game at one point or what is called exposure. If you do something a lot, long enough some adverse things will happen along the way no matter how good you plan.

I had one significant 1/2 mile ride in an avalanche that could easily have killed me that I just chalked up to what Joe calls the numbers game - cumulative exposure. I had been skiing not extreme, but exposed terrain lot that year and although each decision seemed justified I was actually wondering before the accident if I wasn't pushing the envelope too far. Of course, after the accident, I went back and studied what had happened. I even collected old telemetry dating back about three weeks. But when I evaluated what had happened and what I could have done differently, I came to the conclusion that faced with the same situation it would probably happen again if I chose to ski that terrain. It wasn't particularly steep, about 30 to 35 degrees in angle, and it went on a three week old Persistent Weak Layer - a thin and localized faceted sun crust. Had we done a snowprofile or various tests prior to reaching this location the results would have been absolutely irrelevant to the slope that slid. The aspect and elevation were too different. There weren't any obvious signs of instability prior to a catastrophic slow, crunching collapse. Had we stopped to dig a pit in the relevant location, the slope would have slid anyway in the process. It was likely the only large avalanche in the Cascades that day. The hazard was rated low below 7000' except on sun exposed slopes in the afternoon. This slide happened in the morning on an east facing aspect but not in a situation where the sun was warming the snow to anywhere near the melting point. The sun could still have played a role, though, in warming near surface layers and causing stress redistribution in the snowpack.

Check out the avalanches in the Whistler area the last couple of days. It hasn't been snowing much but they did get the strong winds the Cascades got yesterday. Shows the weak layers in the CAC South Coast and Whistler avalanche forecasts. Somebody must have woken up a troll or something.

telemarktalk.com/phpBB/viewtopic.php?t=6...1aebf45faa35e4b39f6b

Big Bertha just slid all the way down to 410 ripping out numerous old growth trees along the way.

Rumor has it that it was a 8 foot crown.

Kempers is a time bomb.

Big Bertha just slid all the way down to 410 ripping out numerous old growth trees along the way.

Rumor has it that it was a 8 foot crown.

Kempers is a time bomb.

Sweet!! About time that it cleared that out again! I wonder if it blew across 410 and went all the way down to the WR road like last time? There was like 30 feet of trees on the highway last time she went off.

When Gary was talking about his big slide ride, I was thinking of the ride I took down Big Bertha wondering if I was going to go all the way to 410.

In the jungle, the quiet jungle the lion sleeps tonight....

This from Mark Moore of NWAC in today's avy forecast:

Finally, it has been a few days since any reported slide activity has involved more deeply buried weak layers or facets near the old late January and early February crust region. The most recently received information regarding deeper slides occurred near Diamond Head to the east of Blewett Pass along the Cascade east slopes last Sunday around noon. This 80-120 cm hard slab released from a 35-40 degree NNW aspect slope (5800 ft) upon approach, although the closest skier was ~100 feet away when the slide released on faceted crystals above the old MLK crust region.  While previous slide activity, continued snowpack settlement, a decrease in heavy loading and continued low freezing levels have likely all contributed to an increasing trend away from larger and deeper releases toward shallower and most recent storm related activity, this most recent release indicates that the layer still exists and can be activated given the right set of snowpack and terrain conditions. In this case, a steep shaded NNW aspect may have provided all of the necessary ingredients for failure, as this slope was probably loaded by strong east to southeast winds received on Sunday, and this transport may have been enough to tip the balance of the overall shallower snowpack over the old PWL. In any case, BC travelers should take the time to investigate the presence of this weak layer before taking large risks on steeper shaded terrain showing no evidence of recent releases.

As is obvious from this incident report, the old deeply buried weaknesses created in mid-February are not gone, and may still fail:

•if stressed by large shocks (e.g., cornice fall, snowmobiles or groups of snowmobilers) ,
•if the overlying snowpack becomes weaker (e.g., heavy rain event to high elevations or sustained high freezing levels leading to a more isothermal snowpack) or quickly applies more stress (wind loading, heavy snowfall event).

Note the simlarity to what happened at Whistler.

Thanks for the good info in this thread. I have a protected slope in mind for this spring. What is the collective wisdom for those February layers being destroyed by warming? Is my usual waiting until after a couple warm close to 60 degree days in town or a thaw freeze cycle and calling it corn season fool hardy in this case? Is waiting through this current warmer weather not enough to destroy those layers?