The year 2020 has been exceptional in many ways, and that extends to the water year (1 October 2019 – 30 September 2020). On October 28 and 29, scientists, resource managers, and planners convened virtually for the Water Year 2020 Recap and 2021 Outlook meeting. This highly collaborative event was sponsored by the National Integrated Drought Information System (NIDIS) and organized by the University of Washington Climate Impacts Group, University of Washington Office of the Washington State Climatologist, Oregon Climate Service, and a large network of collaborators across the Pacific Northwest. The full suite of presentations is available here. For those who just want the major takeaway points, below we summarize the key messages of the meeting as highlighted by Larry O’Neill, director of the Oregon Climate Service and Oregon’s state climatologist, and Karin Bumbaco, Washington’s assistant state climatologist. Also, stay tuned for the official water year assessment in January 2021.
On the whole, water year 2020 was hotter and drier than normal, which contributed to widespread drought and wildfires, particularly in Oregon. These conditions reflect longer-term trends that are projected to become stronger, with consequences for rural and urban communities and for ecosystems.
Drought in Oregon was historically significant
- Across Oregon, water year 2020 was the driest water year since 2001, and the 13th driest in the 125-year record.
- Southern and central Oregon were considerably drier than much of the rest of the state.
- The drought across Oregon became more severe and widespread as the water year progressed. By September 29, only 6% of Oregon was not covered by state-level drought declarations.
- Summer rain from the North American Monsoon was sparse, contributing to drought in central and eastern Oregon.
Flooding in December and February
- Heavy rains in western Washington in December 2019 caused urban and moderate river flooding.
- Flooding in February, 2020, due to an unusually oriented atmospheric river event caused widespread damage to roads in northwest Oregon and southeast Washington.
Snowpack was near normal, but the snow season began late and ended early
- The wet season began late, but snow water equivalent, or the amount of water contained within the snowpack, increased rapidly in January.
- In Oregon, snow water equivalent in early April 2020 was 109% of the median for that time of year.
- In Washington, snow water equivalent in early April 2020 was 111% of the median for that time of year.
- Despite near-normal snow water equivalent in early April, snowpack melted one to three weeks early due to warm temperatures in late April and early May.
A mild autumn was followed by unusually warm weather
- In Oregon, water year 2020 was tied as the 10th warmest on record.
- Temperature in Oregon was +1.9 °F (1.1˚C) above normal.
- In Washington, water year 2020 was tied as the 19th warmest on record.
- Temperature in Washington was +1.5 °F (0.8˚C) above normal.
Strong easterly winds contributed to extreme fire conditions
- On September 7, a warning of extremely critical fire weather in western Oregon and western Washington was issued for only the second time since warnings began in 1998.
- In September, Oregon’s soil moisture was near record low.
- The interaction between the drought and an extremely high-magnitude easterly (offshore) wind event produced extreme fire conditions.
With respect to the water year 2021 outlook, the continental United States is presently in a La Niña advisory. This means that cold sea-surface temperatures in the Pacific Ocean are likely to produce colder and wetter conditions for much of the Pacific Northwest. Let’s hope that 2021 brings widespread COVID-19 vaccination and a solid ski season.
Featured Image: “Mt. Hood in the Spotlight.” (Dudley Chelton, all rights reserved).
Meg Mills-Novoa is CIRC’s program manager and stakeholder engagement specialist.