I've skied for several years in a charity ski race, and one year they had to salt the course 'cause the weather was very warm (probably close to 50). It really did work, the course was much firmer than everything else on the mountain. However, I haven't been able to find any explanation of *why* salting a race course works.
At the highest level, it would seem that the salt is causing some of the snow to melt and refreeze, resulting in a firmer, icier surface. However this doesn't make sense that this could happen when the temp is above freezing. Salt would definitely causing the top layer of snow to start to melt, but now you have a salt solution that freezes at a *lower* temperature than plain water. What's the mechanism that causing this water to refreeze when the ambient temp is that warm?
I'm obviously missing something here, but can't figure out what it is.