A cooler and wetter fall season throughout much of the Pacific Northwest has erased all drought from the region and provided the Cascade and Rocky mountains with a "good start" to a healthy winter snowpack.
So concluded Montana State Climatologist Kelsey Jencso, who offered a look at current climate conditions during an Oct. 28 webinar through NOAA's National Integrated Drought Information System.
Although it may not last, the early snowpack is just one factor that could improve conditions for anadromous fish in the Columbia River. All signs of drought—which factors in soil moisture, streamflows and current snowpack—are gone. The marine heat wave in the northeast Pacific of 2019 appears to be dissipating. And cooler sea surface temperatures since late summer mean El Nino no longer influences the weather.
Jencso said an historic snowstorm on Sept. 29 blasted the two Northwest mountain ranges, setting new records for early significant snow accumulations. The storm dumped up to 10 inches of snow in the Cascades, and as much as 52 inches in parts of Montana, he said. Spokane got snow in September for the first time since 1926.
"Montana saw its second-wettest September on record," he said. Oregon recorded its seventh-highest precipitation for September in the last 125 years and Washington its eighth-highest, he added. However, he noted, some pockets, including portions of southern Idaho and Oregon, had a drier-than-normal month.
The precipitation returned streamflows in many areas to average levels for this time of year, with rivers in the Puget Sound area flowing well above average. Soil moisture content is at least average throughout the region, and above average in some places. There's also twice as much or more snow in much of the Cascade and Rocky mountains compared with the average Oct. 28 snowpack from 1981 through 2010.
Jencso cautioned against making too much of this news, noting that twice the average snowpack in October may only be a few inches in some locations—far different from twice January's snowpack. But, he added, "As a whole, we're off to a pretty good start for winter snowpack because of that storm," he said.
This early autumn precipitation was accompanied by temperatures 3 to 4 degrees cooler than normal over the last month.
But this isn't yet helping conditions for Columbia River chum salmon, listed as threatened under the Endangered Species Act. Chum are beginning to return to spawning grounds below Bonneville Dam, and the Columbia River Technical Management Team (TMT) decided Oct. 30 to begin operating the Columbia River dams to provide more water for them beginning Nov. 4. Those operations initially provide a tailwater elevation of between 11.3 feet and 13 feet below Bonneville while chum are spawning.
TMT Chairman Doug Baus reported that according to short-term forecasts, the augmented flows aren't likely to come from precipitation. He said forecasts over the next 10 days predict precipitation in the Columbia Basin will be 50 percent of average or less, and only 25 percent of average in the southern portion of the basin. The freezing level is expected to drop to between 2,000 and 4,000 feet, so some precipitation will fall as snow, which won't boost streamflows.
Tony Norris, TMT member representing the Bonneville Power Administration, said on-the-ground observations have shown that, in addition to augmented flows from Grand Coulee Dam, the chum below Bonneville Dam also require flowing springs and access to Hamilton Creek in order to start spawning.
TMT member Joel Fenolio, representing the Bureau of Reclamation, cautioned against pumping water through Grand Coulee earlier than necessary for chum, noting reservoir operators are also looking to hold back some of the water for future fish needs. He said hydrologically, inflows into Lake Roosevelt are similar to last fall, at 20,000 cfs or less.
But even if streamflows are similar, other conditions are far better than in October 2018, when only 13 percent of the region showed no signs of drought. The remaining area included 12 percent in extreme drought, 25 percent in severe drought, 22 percent in moderate drought and 29 percent considered abnormally dry.
This October, all signs of drought have disappeared, and only 1.42 percent of the four-state area is considered abnormally dry, Jencso said during the webinar. That abnormally dry area lies in the far north of Idaho's panhandle. The rest of Idaho, along with all of Washington, Oregon and Montana, currently exhibit no drought conditions.
Three months ago, 55 percent of area of those four states showed no drought conditions, while 3 percent was in severe drought, 19 percent was in moderate drought and 22 percent of the region was abnormally dry.
As for the long-term forecast this winter, Mike Halpert, deputy director of NOAA's Climate Prediction Center, said ENSO-neutral conditions—the absence of either El Nino or La Nina—have a 55 to 60 percent chance of continuing through this winter and into spring, bringing more typical winter weather.
In general, he said, the region has equal chances of average, above-average or below-average precipitation from December through February. The temperature forecast slightly favors a warmer-than-average winter, with a December-through-February forecast showing a 42 percent chance of above-average temperatures in the region, a 33 percent chance of near-average temperatures, and a 25 percent chance of below-average temperatures.
The ENSO-neutral—i.e., El Nino/Southern Oscillation-neutral—conditions are based partly on cooling sea-surface temperatures at the equator, which are still above average across the western and central Pacific Ocean, but below average in the eastern Pacific Ocean.
Cooler ocean temperatures also play a role in what appears to be a diminishing marine heat wave. This summer, scientists at NOAA Fisheries reported concerns about a new marine heat wave with ocean temperatures as much as 5 degrees higher than usual, in an area stretching from off the coast of Southern California to Alaska.
The agency now reports the so-called Northeast Pacific Marine Heatwave of 2019 is still present, with warmer-than-average temperatures persisting from the Washington coast to Alaska and the Bering Sea. But sea-surface temperatures have now cooled along the coasts of California and southern Oregon. The heat wave is now smaller and farther from Washington's coastline.
NOAA Fisheries spokesman Michael Milstein said that should be good news for the Columbia's salmon and steelhead.
"The cooler it is, the more upwelling that is taking place" he said. "And that's better for fish because there's just much more for them to eat when they get out there."