VAWS Webinar – Assessing Shifts in Alaska Rain-On-Snow Winter Seasonality

Rain falling on existing snow can produce ice layers that persist until spring, threatening transport, wildlife and power infrastructure in Alaska. Sparse observations and mountainous terrain make these events difficult to characterize. Tricia Hutton presents an analysis using high-resolution reanalysis for winters from 1950 through 2022 to determine their distribution and timing. Most events occur in November and December, with coastal areas experiencing more frequent events and larger rainfall accumulations than the interior. The analysis identifies a seasonal shift toward more December events, increasing the formation of persistent thick ice. These findings inform planning for community safety, infrastructure and ecosystems under a changing climate.