La Niña 2020: A Colder Winter Weather Outlook for Corvallis, Willamette Valley
A La Niña climate pattern has developed this year, which could lead to colder and wetter winter weather throughout the Pacific Northwest in comparison to the past two years.
According to National Oceanic and Atmospheric Administration’s Climate Prediction Center, La Niña is a natural ocean-atmospheric phenomenon marked by cooler-than-average sea surface temperatures across the central and eastern Pacific Ocean near the equator – the opposite of El Niño, which features warmer-than-average sea surface temperatures in that region. Tropical Pacific seasurface temperatures have already been colder than the previous two autumns, and the NOAA’s Climate Prediction center expects La Niña to continue at least through the winter.
What does that mean for Oregon? The November 2020-January 2021 Seasonal Climate Forecast by the Oregon Department of Agriculture and the Oregon Department of Forestry said Oregonians should prepare for “markedly more volatile weather than we had the past two winters, which were tempered by El Niño conditions.” There should be a transition from relatively-mild conditions in November to relatively-cold weather from about Christmas through January.
The wave of storms in the coming months will help ease drought conditions throughout Oregon, and will conclude the historic wildfire season that raged through the state this year. However, heavy rains could leave some areas susceptible to landslides and flooding.
The last La Niña appeared during the winter of 2017-2018, followed by El Niño in 2018-2019. La Niña conditions typically brings above-average precipitation and colder-than-average temperatures to Oregon. AccuWeatherreports that mountain snow and stormy conditions may arrive in late fall for the Northwest. Along the I-5 corridor from Medford to Seattle, there will be several opportunities for accumulating snowfall.