Oregon has experienced an unusually long warm spell this January, contributing to very low snowpack – especially in the lower elevations of the Cascade Mountains – that could create problems for farmers and others dependent on summer stream flows.
Low “snow water equivalent” levels in January aren’t necessarily a cause for alarm, scientists point out, but this winter’s El Niño conditions may make it difficult to recover.
“From past experience, we know the chance of rebounding from early snowpack deficits during an El Niño year are pretty small,” said Philip Mote, director of the Oregon Climate Change Research Institute based at Oregon State University and an OSU atmospheric scientist.
“In 2005, we had about 50 percent less precipitation than normal and the snowpack was 80 percent less than average in some areas because much of that precipitation fell as rain,” added Mote, who also directs the Oregon Climate Services office at OSU. “Luckily, it turned cold and wet that year in late March and a series of storms came through, essentially rescuing the farmers in most counties.
“But this year, we are experiencing the strongest El Niño since 1998.”
Typically, when snowpack is low in February, the snowpack doesn’t recover completely, agrees Jon Lea, state hydrologist with the U.S. Department of Agriculture’s Natural Resources Conservation Service. But there may still be hope, he added.
“There have been a few times where we had very timely spring and summer rains, which really helped the state’s water supply in the absence of a good snowpack,” Lea said. “This year, the snowpack is well-below average in the Willamette and in the northern Oregon Cascades. Elsewhere in the state, it has been slowly – very slowly – improving, though it’s still below average.”
Lea did his next snow survey on Thursday, Jan. 28. The finding: the snow-water equivalent in the Willamette Basin stands at 48 percent of the long-term average.
This January has been one of the warmest on record in Oregon and, in fact, some parts of the state could notch their warmest January ever. Through Jan. 26, Medford’s average temperature in January was 45.8 degrees, which is nearly eight degrees above normal and higher than the 45.13 record average for the month, set in 1995.
Eugene (45.9 degrees) and Salem (46.4) are within a degree of their warmest January, both set in 1953 – and roughly seven degrees higher than normal. Portland is 5.4 degrees warmer than normal, though its average January temperature of 44.9 is well below its 1953 record of 47.31 degrees.
The impact of the warm temperatures, along with a cold, dry January, has created snowpack levels that are about 50 to 70 percent of normal, according to the Natural Resources Conservation Service. The easternmost part of Oregon is in the best shape, closer to 80 percent.
“What is of particular concern is that the high January temperatures have taken a whack out of the lower-elevation snowpacks,” Mote said, “and that low-elevation storage is critical to water supplies later in the year. If you ask skiers about the snow, they’ll say it hasn’t been that bad this winter. But there hasn’t been much snow at the 2,000- to 3,000-foot levels and that could create problems.”
Kathie Dello, a research assistant with the Oregon Climate Change Research Institute, said that the state’s near-record temperatures this month aren’t because of extraordinarily warm weather.
“It’s not that it’s been warm, shirt-sleeve weather,” Dello said, “it’s just that it hasn’t been very cold.”
Mote and Dello point out that Oregon typically sees 5-9 days periods of warm and cool weather patterns in the winter, but those cooler periods just haven’t materialized since a 10-day cold snap in December.
“If you look at the next few weeks, the predictions are for generally warmer weather,” he said.
The current El Niño is classified as “strong,” by the National Oceanic and Atmospheric Administration.
Sea surface temperatures in the El Niño region of the tropical Pacific Ocean were more than 1.8 degrees (celsius) above normal, the highest since early 1998, Mote said.
OSU oceanographer Kipp Shearman said local sea surface temperatures this January at the Stonewall Bank buoy 20 miles offshore have ranged from 10.3 to 11.2 degrees celsisus – slightly above the long-term average for January of 10.2 degrees, though far short of the powerful El Niño of the late 1990s.