Interesting day in Mineral Fork.

December 29th thru January 10th was a period of high pressure in the Salt Lake Valley, where the low elevations trapped the cold air and smog (car pollution) in the valley bottoms. In the higher elevation above the inversion you had sunny calm, clear, and cold conditions. This high pressure allowed the snow surface to become weak and faceted (sugar snow) through vapor transfer, driven by temperature gradients in the surface snow. Meaning, that the surface snow grains Metamorphosed (changed) into angular grains known as near surface facets (NSF). Near surface facets are a notoriously dangerous weak layer in the Wasatch range. If buried NSF can become a sliding surface for the denser snow above. These NSF were buried on the 10th of January with an unusual storm that brought 2-3ft of snow to the benches and lower canyons, while the higher elevations were left with just 10-15 inches of snow.

These were the same weather factors that led to two very close calls in the Mill Creek drainage.

Observation links:

utahavalanchecenter.org/avalanches/accident-west-porter
utahavalanchecenter.org/avalanches/accident-depth-hoar-bowl

The recent 6-8 inches of snow was enough new weight to make the old January facets cranky (at least where I was). The January 10-12th storm has now settled into a 10-12 inch four finger slab over the very weak faceted snow. I counted six notable collapses in my travels.

The weather forecast calls for an additional 20-30 inches of snow with 1.00-2.00" of water. Winds will be steady with hourly average speeds of 20-30 mph at the 9,000ft ridge lines. I'd suspect that if this weather forecast comes together, Mineral Fork will be a scary place to be and I would think that a natural avalanche cycle wouldn't be out of the question.

The variability and uncertainty of the snowpack demands respect. The new storm snow is overloading (stressing) the complex and variable snowpack across the Wasatch Range.

Stay safe

Trent Meisenheimer

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