This spring in Colorado there was a pattern with the kinds of avalanches people were getting involved with: dry snow avalanches in a spring context. There are a couple nuances with this specific setup that can help us operate more effectively in the spring.
First let’s bring it back to the fundamentals of new snow settlement.
When new snow falls it has inherently unstable grain form. The stellar dendrite—the perfect snowflake—it is predisposed to settlement. The large surface area to volume relationship in the shape of a stellar is fundamentally unstable and immediately it begins to deteriorate.
Soon as it falls the stellars begin to decompose into a more stable shape with a better surface area to volume relationship on its path a ‘rounded grain’. As they deteriorate, they begin to form bonds and loose pore space becoming more dense. This process generally referred to as ‘settlement’ causes the new snow to begin taking on the slab like properties that allow fracture to propagate and avalanche conditions to evolve.
As the new snow is settling amongst itself its also brining to bond to the underlaying old snow. This new/old interface is the key to dry snow avalanches being so reactive in the spring.
Snow likes to bond to like snow. The more similar the characters of a grain the more effectively it can bond. This means that new dry snow can bond out very effectively on a old surface of relatively new snow. Sometimes this can be only a matter of hours. In the case of spring snow surfaces, with solar tilts, we have old surfaces composed of crusts and melt forms the new dry snow does not bond well at all.
So not only do we have old snow interfaces that don’t allow new snow to bond well we are dealing with a much higher hotter sun. This heat leads to rapid settlement in the new snow. Couple this with poor bonding to the old snow surface and get slopes ready to easily and rapidly shed large snow volumes.
This combination makes it easy for snow volumes to grow rapidly as every small avalanches immediately entrain all the new snow available below them as they run.
On solar aspects with seemingly small snow volumes can turn into fast ticking time bombs as the sun warms them up. It’s easy to find parties booting up a solar couloir at around 10 am as the snow quickly transforms from a few inches of low density snow into a large loose/small slab avalanche as the sun hits the slopes. We also see the sun making snow shed off rocks and create a ready supply of natural triggers.
In these conditions I tend to prefer shaded aspects as the new snow settles slower and bonds with the underlying old snow more effectively.
The other options is to be entering slopes from the top, as these problems can be very manageable before they grow in size during their flow. Managing a six inches of snow in this character from the top is very reasonable, but that same avalanche will quickly have an unmanageable volume after a short flow.