White Peril: This RKO Pathé Screenliner show members of the 'snow patrol' at work in the Cascade Mountains of Washington state. At designated places, they measure snowfall and take core samples of the snow and measure its weight and density. They also measure river currents in relation to the snowfall. The data is used by the U.S. Geological Survey to help determine how the water runoff in the spring will translate into supplies of fresh water.