On Dec 25, 11:20*pm, Adrian wrote:
I spent a wonderful afternoon this afternoon, walking in the mountains,
in the gorgeous sunshine. Walking paths no-one had walked for over a
week (well, since the snow fell). There are a number of pictures up on
the web:http://users.aber.ac.uk/ais/weather/pics/2010-12/

What intrigued me - and shows in at least four of those pictures - is
the crystals that have formed on the surface of the snow. I don't recall
seeing anything like this before, They are actually quite large; I
suppose maybe up to an inch in height. What causes these to form?
Condensation from the air crystallising onto the surface I guess, but
why in such strange patterns?

These crystals made for a beautiful scene, with the low sun reflecting off
them, making the snow really glisten (is this what people mean when they
talk about glistening snow?), like fairy lights dotted across the snow.

All in all, a truly beautiful and amazing Christmas day.


If you get the surface with these crystals (surface hoar) and then
another drop of snow it can be a big avalanche risk as the crystals
form a weak layer in the snowpack. They were all over the place in
Glen Lednock, saw them on Friday, very fine and delicate, and not as
large as you describe.

http://www.avalanche-center.org/Educ...rface-hoar.php
http://www.fsavalanche.org/Encyclope...rface_hoar.htm