By Kathie Dello, Associate Director of the Oregon Climate Change Research Institute, Deputy Director of the Oregon Climate Service
For the first time since 2011, the Pacific Northwest (Oregon, Washington, and Idaho) is not registering any sign of drought on the US Drought Monitor. There are also no signs of a potential drought looming on our horizon. None. We’re in the clear.
So, why the good news about drought? It’s about the precipitation—the cold variety. We got a lot of it this winter, much of it came as traffic stopping, school closing snow storms, leading to what we can only describe as this water year’s long, cold, and wet goodbye kiss to the drought.
Here’s what we know:
The water year starts every calendar year on October 1 (ending on September 30 of the following calendar year). Here in the Pacific Northwest, the heaviest months for precipitation are November, December, and January. This reign of heavy rain and snow is followed by a transition into drier weather in the late winter and spring months. While the amount of precipitation that falls varies from west to east across the Pacific Northwest, this seasonal cycle is typical for our entire region. This year we saw just the opposite of this typical pattern. Precipitation came early and stayed late.
This water year, the normally drier months of October, February, March, and April were wetter than normal—much wetter—across the entire Pacific Northwest. Idaho just recorded its wettest April in recorded history. And while rain during these months is not uncommon, the amount that we received this water year skewed heavily toward the higher, wetter end of the spectrum.
Indeed, Seattle and Portland had their wettest and second wettest Octobers on record, respectively. However, unlike what we might expect from a typical water year, the wet wasn’t confined only to the west of the Cascades. It was also exceptionally wet inland. October 2016 was the wettest month on record for Spokane by quite a bit. The city recorded 6.23 inches for October, beating out 1947’s standing record of 5.41 inches by over half an inch.
Unfortunately, heavy precipitation that early in the water year didn’t end the drought—that would come later—and it arguably did more harm than good.
Rain early in the water year can be beneficial, provided there’s a place to store it. However, most of this October’s precipitation fell as rain, not as snow that can accumulate in the mountains and then melt and run off later in the year. That meant much of the benefit of the extra, early precipitation was not only lost as run off, but led to fall floods in many parts of our region. When the normally wet months of December and January came, the pattern changed again.
In December and January, colder-than-normal air settled in across the Pacific Northwest, leading to snow in the mountains as well as at the lower elevations. Like rain in October, snow in December and January is not uncommon. However, the snow we ended up getting was most definitely atypical. The especially cold temperatures meant snow accumulated not only in the mountains, as it typically does, but also in many of the region’s cities, which doesn’t happen that often, meaning most cities aren’t really prepared for it.
The Willamette Valley was a case in point. The valley saw multiple instances of snow, sleet, and freezing rain throughout the winter, with the commensurate road closures and stranded motorists in tow. Nearly a foot of snow fell in downtown Portland in mid-January, one of several snow storms that led to multiple school closures and an all but complete shut down of the metro region for days in what locals referred to as “snowpocalypse.” A mid-December ice storm in Eugene was one of the worst in decades. While in eastern Oregon and western Idaho, snow and ice pummeled onion storage facilities, leading to hundreds of millions of dollars in damages. This no doubt added insult to injury for an area that had been plagued by drought since 2012.
It’s not an exaggeration to say that what we’ve seen this water year really flipped the script from the drought years. Whereas many of the drought years, especially 2015, were especially warm, this winter was especially cold. In fact, this winter was the coldest winter on record in the Pacific Northwest since 1992/1993. Couple that with the extra precipitation we received this water year and you get a banner year for snowpack in our region’s mountains and a banner year for number of snow days in our cities’ school districts.
Okay, before you rush off and grab a snowball and vehemently attest that this winter’s cold, cold weather means climate change is poppycock, let’s deconstruct this some more. Yes, this winter—that’s December, January, and February to climatologists—was the coldest in 24 years.
However, this winter is very probably not setting a new trend. The vast majority of the Pacific Northwest’s record-breaking cold winters happened prior to 1950. In recent decades, winters, like the years they’re attached to, have trended warmer, not colder.
So what was different about this year? Let’s start with this year’s La Niña. La Niñas—the other side of the El Niño climate coin called the El Niño Southern Oscillation (ENSO)pattern—tend to mean cooler, wetter weather in the Pacific Northwest. This was the case in 2011 and 2008.
Next there’s the issue of high pressure. During this winter, when high-pressure systems settled in the region, they tended to do so over land and not over the ocean. This was significant because when high pressure forms over the interior continent in the winter, it often leads to cooler temperatures from a clockwise flow around the pressure center. This leads to cold air from the land being dragged into the region. For the Willamette Valley this winter, that pattern frequently meant the region received the cold, easterly flow from the Columbia River Gorge as opposed to warmer flows from the ocean.
So what’s next for our region’s climate?
While it’s now officially spring, winter nonetheless seems reluctant to release its grip, although warmer temperatures have made their return. Climate stations in Oregon and Washington continue to set records for number of days with measurable precipitation over the past six months. The good news? There’s water in reservoirs that were empty or nearly empty in previous years, and there’s plenty of snow in the mountains. It seems the toughest days of both the drought and this winter are behind us. Eventually, the rain and what remains of this water year’s long, cold, wet goodbye kiss to the drought will stop too.
In the meantime, goodbye, drought! Be seeing you.