2.2.1 Introduction

This plot shows how seasonal snowfall amounts vary across sites in the western United States, with striking differences occurring during some ENSO events.

Annual snowfall at 3 selected US western mountain sites

The peak times for annual snowfall maxima vary from early to late winter based on factors such as the typical progression of the jet stream, surface storm systems, and moisture sources. For example, the Cascade Mountains receive most of their snowfall in December and January, while the Denver area east of the Rocky Mountains peaks in March.

What causes these variations? What creates the different types of snowpack found around the world? In the previous section, we examined the global-scale factors that play a role in snowpack development. Now we'll explore the regional- and local-scale factors that have an impact, such as geography, precipitation type, and wind.