A Study of Significant Late Season Snow and Precipitation Event Behavior in the White Mountains

Evidence from observational data and climate modeling studies indicate significant snow events are likely to continue at a steady or increasing rate in the Northeastern U.S. This is despite a shortening winter season in the region due to climate change. This study investigated how significant late-season snow and precipitation events have been changing in frequency, intensity, and duration in the White Mountain region. This investigation analyzed data from 1995 to 2024, focusing on the period of March 1^st to June 30^th for each year. Data originated from the B16 daily archives kept at the Mount Washington Observatory and observations collected at the Pinkham Notch Visitor Center. This included daily snowfall, precipitation, and snow depth recorded for each day during the period of study. 90^th percentiles were calculated for daily data and separately calculated for three and five-day running averages to capture multi-day events. Code was generated using Python to run calculations and generate visualizations. Multi-day events were verified manually using upper-level and surface charts along with radar data from the National Center for Environmental Information. Significant snow and precipitation events stayed consistent at MWO while snowfall events slowly increased and precipitation events remained the same at the Notch. Event intensity was similar between MWO and the Notch with MWO observing more outlying events. Significant events typically lasted two to three days and no longer than five days. Understanding these trends can increase forecaster knowledge and accuracy and better inform the public about these impactful events.