Turns out the snowfall the Portland, Oregon area saw on Monday, April 11 wasn’t unprecedented as some suggested.
That’s according to Oregon State Climatologist Larry O’Neill of the Oregon Climate Change Research Institute (OCCRI). O’Neill is also an associate professor at the College of Earth, Ocean, and Atmospheric Sciences at Oregon State University (OSU).
On Tuesday, O’Neill sent an email to Discrepancy Report saying:
Technically there is a listing for this 0.5″ of snowfall at KPDX on May 8, 1953. A few neighboring near Portland also recorded snow around this day, such as Oregon City and Estacada.
Going a little more broadly, Portland has received measurable snow in April before, even if it was only measured as a trace at KPDX. Yesterday I dug through Oregonian press accounts and found a few instances of April snow.
Email sent by Oregon State Climatologist Larry O’Neill on April 12
Some of these accounts reference old weather bureau statistics that I plan to try digging up.
April snow in Portland and the Willamette Valley is definitely not common, but it certainly isn’t unprecedented.
Email sent by Oregon State Climatologist Larry O’Neill on April 12
“In 82 years of record keeping, #PDX had never recorded more than a trace of snow in April,” The National Weather Service’s Portland, Oregon office tweeted Monday. “That ended today.”
The agency said the region saw several inches of snowfall which was blamed for power outages, road, and school closures in many areas.
To find out whether there’s a connection between the storm and climate change Discrepancy Report emailed O’Neill Monday.
Nick Siler, assistant state climatologist at OCCRI and an OSU assistant professor, responded to Discrepancy Report’s inquiry that day saying in part:
Larry O’Neill forwarded me your email. I’m not aware of any evidence that would suggest this event is related to climate change. It’s a record-breaking event, but it’s not *that* far outside the norm—e.g., I believe Seattle has recorded snow this late in the season before, or close to it. That said, there is some evidence that La-Nina-like trends in tropical SSTs (sea surface temperatures) have contributed to somewhat wetter and cooler late winters/early springs in the PNW over the last few decades, offsetting some of the effects of global warming (e.g., see https://doi.org/10.1029/2018GL081080). The prevailing view is that these SST trends are the result of low-frequency natural variability, but reasonable people disagree. …
We clearly found that trends in the atmospheric circulation and SSTs had the largest impact on snowfall accumulation in the late winter (Feb-Mar), and almost no impact in the early winter (Oct-Nov). We didn’t look at April because we were only focused on the traditional accumulation season, which ends April 1. But it would stand to reason that the late-winter results would bleed over into early spring as well.
Email sent by Nick Siler, assistant state climatologist at OCCRI, on April 11
