http://scientistatwork.blogs.nytimes.com/2010/12/15/katabatic-winds-of-antarctica/?hp

Katabatic winds are an Antarctic specialty. They are a phenomenon
of nature, but they are no friend to those of us who are mere summertime
outsiders. Katabatics form by cold air masses descending onto the ice cap and
spreading along the ground. There is nothing to stop them, so they form
sheet-like rivers of air and blowing snow. It seems like you are in a relentless
storm, but it’s odd because when you look up, the sky is most often sunny and
blue, seemingly benign. The katabatics will keep up until the cold air mass
dissipates, or until there is a countervailing push from the ice shelf side of
the mountains. The hardest part about dealing with katabatics is that they can
last for days on end, unlike most storms we are familiar with at home that come
with short-lived frontal systems.