The thawed corn snow we found Thursday proved elusive in today's colder -10°C temperatures. We turned around on the way to some southerly aspects where we hoped we might still find softer snow because the snow on the way was so icy that we were worried a fall would result in a slide for life. The buffeting from NE winds gusting over 30 m/sec did nothing to make us feel more secure in our footing.

Instead we did some studies on faceted melt freeze grain formation in Heavenly Valley, just outside and W of Eaglecrest. We tested a shaded NE aspect on a gentle 20° slope.

The surface was lightly rippled, not runneled, and hard enough that it would not disaggregate when rubbed hard with a gloved hand. The density of the top 5 cm was a high 420 kg/m3. Other areas had a softer and more sugary surface, spatial variability that is common with faceted melt freeze.The snow layers to 60 cm depth below the surface were knife hard, so hard we had to dig by chipping pieces out with the corner of our shovel.

Yet even at the high density and hardness of our sample site, the top 1 cm had not only crisp well developed facets but also striations, lines of crystal growth clearly visible on the crystal faces. Both are signs that the snow is changing to faceted grains. Below the surface all layers observed had well formed facets, but no striations.

Faceting in melt freeze layers is not described in the literature or specifically mentioned in the international classification scheme for snow, but we have found over the last 20 years that faceted melt freeze layers cause large and difficult to predict avalanche cycles in our region, so we have been studying the process at every opportunity.

The temperature gradient, which drives the vapor flow for facet formation, averaged 15°C/m over the top 60 cm and reached 30°C/m in two sections. A gradient of 10° C/m is enough to drive facet formation in a snowpack near the freezing point.

These layers have tremendous strength when frozen, so avalanche danger is about as low as it gets with snow on the ground, but beware of the high probability of a weak bond with the next snowfall, which is forecast to begin tomorrow. Travelers should be cautious also about high speed sliding falls on the icy layer.