The 13 inches includes 2.19" of water, which equates to a water content of 17%. Yup, Cascade Concrete. Let's look at how the NAM and Alcott snow algorithm verified at Alta based on yesterday morning's forecast. The NAM called for 2.06" of water by 7 am this morning, very close to observed. That is a remarkable forecast. I figured we'd come up a bit short of that, but am not going to complain about coming in on the high side. The Alcott snow algorithm called for an hourly snow water content of 14% for most of the night, decreasing for to 9% this morning, yielding 15.6" of snow. It had the right idea, but clearly did not go for 17%, although the Utah Avalanche Center (UAC) suggests that most reports were in the 13–15% range. Settlement might be inflating the water content numbers at CLN some as we're now getting well into the storm. Note how the snow interval observation has hung in there at 13" even as precipitation continued.
Totals decrease on the Park City side of the range. This likely reflects precipitation shadowing from the strong westerly flow and the strong gradient in precipitation with elevation, especially early in the storm when there was a lot of dry air at low levels.
It looks like a hard shell day today. It is balmy this morning, with a freezing level near 8750 feet and temperatures of 33ºF at the base of Alta and 34ºF at the base of Solitude. Flakes will be wet below 9000 feet.
Orographic effects were excellent for a warm front, looks like the NAM did well as far as mountain precipitation. The main forecast "miss" in this case was with valley precipitation and snowfall, as the lower level air mass was much warmer (about 10 F warmer at KSLC yesterday) and a bit drier than NAM soundings suggested. At any rate, nice to see that we are building up a base for skiing.
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