Abstract ID: 3.11285 | Not reviewed | Requested as: Poster | TBA | TBA

Snow droughts, or periods with below normal snowpack, in the mountainous regions of the western United States can cause significant impacts such as reduced seasonal water supply, shifts in timing of runoff, reduced summer soil moisture, and increased summer and fall wildfire danger. Temporally coarse indicators of snow drought, such as peak snow water equivalent (SWE) or seasonal snowfall totals, are often used to examine snow droughts retrospectively; however, the impacts of single or multi-day snowmelt events on early- or mid-winter snow drought development and acceleration are less understood. In mid-winter of 2024, a major snowmelt event occurred in the Cascade Range of northern Oregon and Washington with some locations losing 30-50% of their total snowpack (5-20 cm of SWE) in just five days. The snowmelt event was initiated by a rain-on-snow (ROS) event that was then followed by continued snowmelt for several days with no precipitation occurring. This study will unravel the drivers of the overall snowmelt event including looking at the upper atmospheric circulation patterns and surface temperatures associated with the ROS event and the mid-winter heatwave that followed, placing the snowmelt event into context relative to past events. We will analyze the frequency and magnitude of this event as it relates to historical patterns. Mountain observations from the Snow Telemetry (SNOTEL) network will be used for SWE and precipitation and ERA5 reanalysis will used to examine circulation patterns and air temperatures. Using snow drought phase diagrams and other methods to track seasonal trajectories of snow drought and water volumes, we will quantify the impact of the multi-day snowmelt event on warm season drought and water supply deficits that occurred during summer 2024. Results have potential implications to improve drought monitoring and prediction in the mountains and provide a broader context for water management in a changing climate as warmer temperatures and ROS events are projected to become more frequent and severe.