to Deluge: A Lesson in Communicating High-Impact Weather During a Relentless
Stream of Atmospheric Rivers
Courtney Obergfell, National Weather Service - WFO Sacramento, California, Sacramento, CA
Faced with several years of extreme drought, interior Northern California had not seen a “normal” winter in quite some time. That was all about to change as the winter of 2016-2017 rolled around. Over the course of the 3 months, NWS Sacramento was faced with forecasting and communicating a relentless stream (some 15-20) of atmospheric rivers. Subsequent rises on area waterways caused flooding impacts, levee breaches, and water levels not seen since the floods of 1997, a benchmark for many area residents. As a result, the spillway at Lake Oroville dam was damaged and a lake at capacity forced the use of an auxiliary/emergency spillway for the first time in the history of the dam (built in 1969). Erosion to the auxiliary/emergency spillway prompted the threat of spillway failure and large-scale evacuation of communities downstream ensued. In addition to continuous heavy precipitation, saturated soils and several rounds of strong winds caused tree/property damage, power outages, and landslides which prompted several long-term closures of mountain highways across the region. Such a long duration of high-impact weather caused a need for specialized decision support services and collaboration in communication at NWS Sacramento. Because of strong relationships with local partner agencies developed during quiet weather, consistent and strongly-worded messaging aided in heightened awareness and response. This talk (or poster) will focus on successes of this messaging and lessons learned for future high-impact events.