I-90 Closed for Epic Snowfall!

That is an interesting article. I can't imagine pits being effective to evaluate layers more than 4 feet down.
I am curious though why it suggests avoiding shallow snowpacks in these situations, 200cm, or 79 inches roughly?

Somebody correct me if I'm wrong, but I think it's because the weak layers get less likely to trigger (in general) the deeper they get buried. More big dumps, please!

I sure don't want to dig any pits that deep. In fact, I don't want to dig any pits at all.

Well that does make sense, more weight, more compression, etc. But I would think the shallow snowpacks would benefit a little from small anchors like stumps and things as well as being easier to evaluate.

I thought it had to do more with the way the weight of a skier is distributed deeper in the snowpack. Deeper layers "feel" less force than shallow layers. The weight of a skier becomes less significant to deep buried layers

Their warning may also be due to the fact that thinner snowpacks strengthen thermal gradients - crust faceting is, as I understand things, driven by gradients. Ergo, the nasty crust layers become nastier over time where it's shallow and the ground's warmer than the sky/air.

Avy professionals please chime in here!

You're exactly right, TS. A shallower snowpack is more likely to be affected by a strong temperature gradient, especially in areas where the air temp gets very cold. Not typical in the NW, but this year has been different. And in Canada they are more likely to experience that large differential.

MD2020, great illustration and analysis. I've seen that somewhere before. The other thing about shallow snowpacks is that even though there can be more anchors, there are also typically more trigger points. Snow tends to facet around rocks and trees, creating a weakness where propagation can begin.

As to the effectiveness of pits to evaluate deep instability: at Stevens we dug down to the crust that formed during the week of no snow that occured before this last cycle. The intention was to test that layer in an area called the Susan Jane traverse, at about 5400' with a North aspect. Our pit was 9 feet deep! In order to even evaluate the characteristics of the layer we removed the top 5 feet of snow and then performed CT and shovel shear tests as you normally would. A melding of intuition and science is an understatement of how to interpret these types of avalanche problems, watching the experienced forecasters work was very interesting.