Road closure to mitigate avalanche danger: A case study for Little Cottonwood Canyon

Avalanche forecasters make decisions to close the Little Cottonwood Canyon Highway to vehicular traffic in the case of avalanche danger. A statistical model improves forecasting performance. Conditions do not vary simply by day as implied in the statistical model, but the development of the snowpack varies substantially among seasons. There are persistent features of a snowpack which affect avalanche danger within each season. Forecasters’ performance also varies substantially over seasons. This paper attempts to incorporate this feature into an operational method to develop seasonal weights to combine data and expert opinion.