Regional Impacts of Sea Surface Temperature on Snowfall During the 2024/2025 Early Winter in Japan

Abnormally heavy snowfall occurred over central and northern Japan during the winter of 2024/2025, when sea surface temperature (SST) over the Sea of Japan was anomalously high in December to mid-January. We investigated how the SST influenced precipitation, snowfall, and snowpack characteristics during this period. Two numerical experiments using the Weather Research and Forecasting model were conducted: realistic and sensitivity experiments in which SST anomalies over the Sea of Japan were removed. We determined that high SST over the Sea of Japan in this winter enhanced precipitation and snowfall along the western coastal regions of Japan, although the response exhibited regional differences. Precipitation and snowfall increased more in northern Japan than in central Japan. Furthermore, snow density increased in northern Japan. These findings highlight that anomalously warm SST over the Sea of Japan can influence not only snowfall amount, but also snowpack characteristics, with spatial heterogeneity.