Snow stability

A snowHead

Fed up of reading about facets and dangerous weak layers. When do we ever get a snow cover that is free from these flaws, so asked my wife. Not the easiest question to answer I realized as I tied myself in knots!
Any clear and simple thoughts on the matter gratefully received.

A snowHead

Spring - the freeze-thaw cycle essentially melts snow crystals into granular pellets with a coating of melt water (corn snow), which then re-freezes into a more homogenous pack when the temperatures drop over night, and repeat... Until the melt water percolates deep enough at which point the avalanche risk rises again wink

Well, the person's real but it's just a made up name, see?

I guess if you could have uniform temps and weather where it snowed steadily but unspectacularly at regular intervals and sun and wind never intervened you'd have a chance of a snowpack without weak layers. But in the real world....

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How will the current warm temps affect snowpack stability? Where it has been freeze-thaw cycling will that have created an icy slidy surface onto which the expected new snowfall this weekend will not bind?

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Depends how wet the storm comes in. Generally wet and sloppy turning to cold and drier is better for a storm cycle in maintaining a cohesive snow pack.

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@hd, it depends - there really is no better answer (though I'm not sure there has actually been much cycling at this point).

What will the temperature be when the new snow starts falling, for example? That will be different at different altitudes and aspects on the same mountain too. How well new and old snow will bond is very different if the new snow starts falling at around 0°C or if the temp shoots down to -20°C 24 hours ahead...

What the warming will have done is hinder the development of facets at the base and surface of the snow, due to the smaller temperature gradient, and possibly transformed some surface hoar that had formed previously - though there are plenty of cold/shaded/north-facing/high places where it is still growing.

This is an extreme example (from this time last year), from a very cold part of Stubaital that doesn't get any sun at this time of year - it's as fragile as glass, so you can image what would happen if 30cm of new snow falls on top of it and a skier drops in...

It's the growth of this sort of crystal that makes Colorado one of the most dangerous places for avalanches - the regular very cold clear nights are why it's sometimes known as a 'surface hoar farm'.

The following photos are from Feb 2016, and show what we had at the bottom of the snow pack at that time (around 1800/1900m). Hopefully this warmer weather will avoid that, though it should be noted that at altitude the development of that sort of weak crystals at the base of the pack is pretty much assured anyway - just hopefully deeply buried enough that it can't/won't be trigger able by skiers.

It's worth following guides/avalanche services/pros/etc on social media (Instagram can actually be really useful for this sort of stuff) in the areas you anticipate skiing to keep up to date with this sort of info as the snowpack builds.

Third paragraph/second photo on gets interesting: https://lawinenwarndienst.blogspot.co.at/2017/11/eine-kaltfront-bringt-schnee-und.html?utm_source=dlvr.it&utm_medium=facebook

After all it is free

@davidof posted elsewhere a French avalanche warning for this weekend.
The major concern being the presence of faceted crystals caused by strong temperature gradient during the last week or so.
Areas that may get skied for the first time as more lifts open, providing access.
Be careful everyone!!

@Rogerdodger, was that warning for the Pyrenees or the French Alps?

Help!!

Snow stability

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