Climatological Context of the Severe Rain-on-Snow Flooding Event of March 2019 in Eastern Nebraska

Abstract

The rain-on-snow event of March 12–14, 2019, in eastern Nebraska was caused by a rapidly intensifying mid-latitude cyclone that resulted in over 80 mm of liquid precipitation and the ablation of over 25 mm of liquid equivalent in the snowpack. The resulting flood caused over $10 billion in damage by some estimates. Here, we sought to evaluate specific dimensions of this event within the broader climatological context to determine how unique the event was relative to a longer period of record. Results suggest that the mid-latitude cyclone had a central pressure over 30 hPa lower than its classified synoptic weather type, leading to greater warm advection and temperature and dewpoint anomalies as high as +8°C and+10°C, respectively. The 3-day sequence of weather types corresponding to the event was observed only three other times over a 1948–2021 period of record, while the 2-day sequence of just March 13–14 occurred just 25 other times. The magnitude of daily precipitation during the event was in the 100th percentile of all rain-on-snow (ROS) precipitation events for 16% of the basin and likely was a primary driver of observed flooding. Similarly, daily snow loss during the event across eastern Nebraska was above the 95th percentile relative to 1981–2021 climatology for most of eastern Nebraska. Collectively, our results suggest the March 2019 ROS event was an extreme event across multiple individual facets, but they were not without climatological precedent. As such, this event is a useful case study for understanding extreme rain-on-snow events across the Central United States.