Below average snowpack expected region wide

From The Columbia Basin Bulletin

Warm and dry has been the story for the Pacific Northwest in recent weeks, contributing to a region-wide snowpack deficit that may continue for months to come, according to speakers participating in a drought and climate outlook teleconference last week.

The discussion, sponsored by the National Integrated Drought Information System (drought.gov), outlined a worsening outlook for drought across the region, particularly in Oregon.

“As a whole, we can say that it has been unseasonably dry and warm across the Pacific Northwest over the last couple months,” said Kelsey Jencso, a Montana state climatologist based at the University of Montana. “Drought conditions have expanded across the Pacific Northwest over the last few weeks.”

“The area that really stands out here is the coastal region of Washington and Oregon,” Jencso later added. “The big story here is the western region of Oregon,” which is experiencing one of the driest three-month periods on record.

The U.S. Drought Monitor shows “extreme” or “severe” conditions to be pervasive across that state, while the other Columbia Basin states of Washington, Idaho and Oregon are in lesser but worsening degrees of drought.

“Snowpack becomes really important, and this becomes the big story across the Pacific Northwest,” Jencso said.

“Generally, we see orange across the board,” he said, referring to a Snotel map depicting most mountain regions in the Columbia Basin as being at just 75 percent of the historic average for snowpack so far.

The hottest spots for low snowpack are in Oregon’s Cascade Mountain Range, which have accumulations at just 25 to 50 percent of average for this time of year. Jencso explained that the snowpack, combined with low soil moistures in the Columbia Basin, will make it difficult to recharge reservoirs going into spring.

“We’ll need to play catch-up over the next few months,” Jencso hopefully said.

Over the last 30 days, the Columbia Basin states have largely had below-average precipitation, with isolated exceptions in Washington and southern Idaho where precipitation has been above average.

The real challenge, Jencso said, may be above-average temperatures that have persisted across most of the basin over the last month, with the exception of southeast Oregon and southern Idaho, where temperatures have been below average.

Continued warm weather could hinder the region’s ability to accumulate snowpack for the spring runoff.

Andrea Bair, representing the National Weather Service’s Climate Prediction Center, outlined how a predicted El Niño weather pattern could perpetuate warmer and drier conditions. Bair acknowledged there is a general perception that El Niño translates to warm and dry weather in the Pacific Northwest, but she emphasized how the strength of El Niño systems can be a driver for weather in the region.

“El Niños are different,” Bair said. “There is a lot of variability in predicting El Niño and the impacts we’ll see from that … When you get into the weak events, things look a lot more washed out in a lot of cases.”

The Climate Prediction Center has issued an El Niño watch, reporting last week that its models are projecting a weak El Niño has a 90 percent chance of emerging this winter, and a 60 percent chance of continuing through spring.

Weak El Niños have historically produced warmer-than-average temperatures, but precipitation has been above-average for the Northwest during more than half of those years. Because of the warmer temperatures, however, all 21 years of recorded El Niño activity have produced far below-average annual snowfall in the region. El Niño is an ocean-atmosphere climate interaction that is linked to periodic warming in sea surface temperatures in the central and eastern equatorial Pacific.

“We’re looking for this El Niño to be weak,” Bair said, later adding, “There is a good shift in the odds that things will be warmer than normal … But with precipitation there’s a lot less predictability.”

The Climate Prediction Center issued on Dec. 20 a new forecast projecting that on a scale of historic averages for the Pacific Northwest, the region will be the warmest and driest in the during January. The center’s seasonal forecast predicts those conditions will continue January through March.