Great isn't it? You wait for snow, and when it arrives it's the wrong type!

There's that old myth about eskimos having X (pick a large number) names for different types of snow, but if you are observant you certainly can see many different breeds of the stuff. Your problem is mostly one of temperature - at around 0 degrees C the snow is often wettish, but go down to -5 or less and it's just dry powder.

Mountaineers are quite well-versed in the varieties (if they have any sense, anyway) because avalanches often result from bad combinations of snow falling in layers. Steep slopes clear quickly, but shallower slopes can build up very dangerous strata of slab, powder and ice. If the snow can sit for long enough, it will normally start to consolidate into a large sheet of ice called neve (there are acute accents somewhere, but I'm going to leave it anglicised). Neve is partly the result of freeze-thaw action, but is also caused by crystal re-formation. Sublimation, condensation and sunshine all add to the mix.

You don't have to go to the mountains to see all this at work - my own back garden has been quite a good snow lab for 3 of the last 4 weeks. It's getting a bit boring now. It's occurred to me that people in countries where snow falls every winter probably don't bother much with snowballs or snowmen!

To form a ball the snow has to melt a bit to bind together.  If it is too cold, it just doesn't stick.  The same principle applies for sledges or skis; contact pressure melts the snow a little to form a sort of  liquid bearing.  It is said that one reason for Scott's disaster in the Antarctic was that it was unseasonably cold, so cold in fact that their skis and sledges would not run, which happens below a temperature of -20°C.  In consequence the team had to use exceptional effort to make progress.

As an erstwhile mountaineer myself I learned that one can never tell for certain if a slope of whatever angle is likely to avalanche.  Because snowflakes are crystalline they key together but fresh snow needs time to bind to the old layer of snow.  This means that the avalanche risk is high within two or three days following a fresh snowfall.  That and on a south-facing slope when the sun strikes it in the afternoon.  The snow also begins to loosen and avalanche as spring approaches as one would expect. 

If snow as it falls is smashed by a violent wind against let's say a rock, the crystals are broken into small pieces to form hard slabs, known as wind slab.  Mountaineers learn to recognise this in particular because clearly it never keys very well to the underlying snow.  Step on it and it is ready and waiting to transport you down the mountain more quickly than you bargained for.