Snow Conditions in the Pacific Northwest: Near Real-Time Monitoring and Future Projections

Abstract

In the Pacific Northwest (PNW), a large part of the annual precipitation falls as snow in the mountains during fall and winter. The winter snowpack is an important reservoir of water in the region, naturally storing water for the dry period during spring and summer. Water resource managers in the region need to keep track of how much snow resides in the mountains and how much moisture is contained in soils. They also need to have an idea of what the future holds in terms of snow accumulation for long-term planning. We describe a near real-time monitoring system of hydrological variables we have implemented over the PNW as part of the Northwest Climate Toolbox, an ongoing project by collaborators in the Pacific Northwest Climate Impacts Research Consortium (CIRC). Furthermore, we examine projected changes in snow conditions in the PNW during the 21st century. For this purpose, we take advantage of a large number of hydrological simulations made as part of a new study to evaluate climate change impacts on the hydrology of the Columbia River Basin. With projected average increases in winter temperature in the range of 2.6°C to 4.8°C by the end of the century, widespread declines in snow accumulations are projected. These declines in snow accumulations are expected to be greatest in the Cascades, especially the southern portion and western slopes, and in the Olympics. Higher elevated areas with historic mean winter temperatures of less than -6 °C show more resistance to climate warming. The choice of climate model seems to be the major source of uncertainty in model results. By comparing the recent snow drought year of 2015 to our projections, we are able to contextualize the future snow conditions in an intuitive way for resource managers. To offer a practical application, we also examine the implications of less snow for ski resorts in the region.