Friday, March 28, 2014
Bonus Season Event Post Mortem
Yup, the bonus season is most definitely here. I did a short tour into a typically popular area of the Wasatch backcountry this morning and didn't see a soul. I even had to break trail (gasp), not that it required much effort. You could find every kind of condition imaginable out there. I had everything from decent powder to dust-on-crust to wind board to spring mank, and that was in just one 2000 vertical foot run. Thanks to the high angle sun and a bit of rime on the aspens, views were quite nice
If you want to become a better forecaster, going back and evaluating your predictions is essential. In this event, Alta-Collins ended up with 15 inches of snow, which is at the bottom threshold of the 15–24 inches I went for on Wednesday. At that time, the 12-km NAM called for 1.08 inches of water and we ended up with 1.27", which yields a mean water content of 8.5%. There are two sources of error in snowfall forecasts. The first is the forecast of how much water the storm will produce. The second is the forecast of water content. I was thinking somewhere in the 1-1.5 inch range for this event, which seems reasonable, but I was also thinking lower water contents (which yields more snow), which in hindsight was probably a bit unreasonable. It was clear that this was going to be an unstable, late season storm and with the resulting convection, it's pretty common to see quite a bit of riming. Thus, assuming lower-density snow was probably unwise. A good lesson learned.
Looks like more snow on Sunday, with some uncertainty regarding the start time late Saturday night or early Sunday morning. They way things look now, Sunday might be a good day to sleep in, read the paper, and then go out once the snow has piled up for a while.