An Elevational Control of Peak Snowpack Variability¹

The records of the seasonal peaks in snow accumulation on 24 snow courses show that the relative variability (measured by the coefficient of variation) is inversely related to elevation in the San Juan Mountains, southwestern Colorado. Analysis on an annual basis shows that this is due to a tendency for the peak snowpack at high elevations to be closer to the long‐term mean while that at low levels is further from the normal. This is true in both above‐normal and below‐normal accumulation seasons. Extrapolation of 20 annual elevation‐accumulation trends suggests that mean accumulation is reached at 4107 ± 186 m elevation. This is approximately the height of the topographic harrier of the San Juan Mountains suggesting that the pattern of variability is a partial function of an atmospheric‐topographic interaction.