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Every morning all winter long, snow rangers in New Hampshire's White Mountain National Forest climb into their snow cat and head 3 miles into the mountainous back country to make a forecast. They are in the dangerous business of forecasting avalanches. Hi, I'm Dave Thurlow and this is The Weather Notebook.

On a recent trip to the avalanche prone Tuckerman Ravine area of the White Mountain National Forest, snow ranger Marianne Bradley showed me that to assess the stability of the mountainside snow pack, she has to dig what's called a snow pit, actually slicing away at some snow with a shovel to expose a smooth vertical cross section of the snow pack:

Marianne: "What we're trying to do is to get an idea of what the snowpack might be like on the steeper slopes without actually going on them. We dig down and look at the different layers in the snow . You see there are a bunch of layers in the snowpack just like there are in a lasagna. There are some thick, snowy layers and some thin, icy, crusty layers. But the crucial thing is to see if the big layers are stuck to a thin layer below. If they aren't, then you've got a weak layer that could separate from the snow below and carry all the snow on top of it down the side of the mountain. That's an avalanche.

So, what we do is isolate and cut down on both sides, and then we'll cut across the back. You know that if you cut across the back and the snow immediately falls away that it is pretty unstable snow."

But today were in luck, no weak layer! In fact the block of snow needed some convincing from Marianne to move at all.

Marianne:"The avalanche danger is low right now."

So, that's the avalanche forecast for this day anyway. But snow conditions can change as fast as the weather conditions. Our show is funded by the National Science Foundation and by Subaru, the beauty of all wheel drive.