Wednesday, February 09, 2011

The Castle Snow Pit and a big temperature gradient!

Howdy Everyone!

This week's snow pit was dug in the Tatoosh Range on the east side of The Castle. General observations: 10 cm of great powder on top of a hard, multi-layered, 10 cm crust. As you can see from the graph there are two thin ice layers with softer snow beneath both. The layer of most concern is between 17 and 20 cm deep. Small faceted crystals (i.e., angular crystals) were observed in this layer, which can be expected due to the large temperature gradient in the top part of the snow pack. (Any time the temperature gradient exceeds 1oC over 10cm, the potential exists for faceting.)

Stability tests did not show any propagation, but failures were consistent at 18 cm. The Rutschblock Test showed a failure at 10 cm (the interface between the powder and the icy crust). But I have to admit, the crust was so icy that I slipped before I could get in a good jump on the block.

In summary, the strong temperature gradient and faceted crystals are signs of instability in the snow pack. However, the near- surface crusts are very strong, and seem to be adequately supporting sun-seeking recreationists. Great skiing conditions can be found where the wind hasn't scoured off the powder. Terrain and conditions will vary, so stay alert out there! More precip is headed our way for the weekend. Get out while you can.