Oregon Winter forecast is good news for irrigation and agriculture industry

Oregon Department of Agriculture — The first blast of winter has hit Oregon this week, but forecasters predict more to come in the months ahead. As the mountain snowpack builds between now and March, farmers and ranchers can expect another summer of ample water for irrigation.

“The odds are there might not be as much snow in the mountains as last year when there was an extremely high amount, but we should have an above average snowpack this winter once again,” says Pete Parsons, meteorologist with the Oregon Department of Agriculture.

That’s good news for agriculture. Oregon does not receive the summer rainfall that helps producers in the Midwest and other parts of the country. Oregon farmers and ranchers must rely on irrigation which, in turn, feeds off streams and reservoirs. A good buildup of snow in the mountains over the winter usually means plenty of water for those who will need it the following summer.

“The snowpack is beginning to build up in earnest this month and will likely be above normal for the whole season,” says Parsons. “We are accustomed to earlier starts in recent years for snow to fall in the higher elevations, but what is going on this year is not unusual.”

Parsons looks at the historical weather record in Oregon to determine the near future. He specifically searches for past years that have recorded similar ocean temperatures. “El Niño” is the name given to the periodic warming of sea-surface temperatures in the tropical Pacific Ocean. “La Niña” describes the periodic cooling of those same sea-surface temperatures. While El Niño is usually associated with warmer and drier-than-normal winters for the Pacific Northwest, La Niña usually brings colder and wetter-than-normal winters to the area with an increased chance for above normal mountain snowpack. Two years ago was an El Niño year. Last year was definitely a La Niña year.

“This year, we look to be on the edge of neutral,” says Parsons. “There have been three winters in the last century with a similar evolution in terms of tropical ocean temperatures as we see going into this winter. Those include the winters of 1929-30, 1974-75, and 1989-90. In those three winters, there was above normal snowpack by the end of the season, even though it was as late as mid-December before the snow began to accumulate in the mountains. That is what it looks like going into the winter of 2008-09.”

This week’s cold snap and snowfall is not only welcomed by ski resorts, it should be seen as a positive to the agriculture community dependent on melting snow next spring.

“By the first of January, about 40 percent of Oregon’s average maximum snowpack is on the ground,” says Jon Lea, hydrologist with the U.S. Department of Agriculture’s Natural Resources Conservation Service (NRCS) in Portland.

After a slow start, many individual basins throughout Oregon are finally recording snowpack numbers for this time of year thanks to the weather that hit starting this past weekend. A week ago, very few sites had anything to report. Those numbers are now generally rising daily and the percentages typically seen this time of year are getting closer to normal. In eastern Oregon, the Owyhee Basin reports a snowpack of 87 percent of average. Harney comes in at 78 percent of average, Umatilla 74 percent of average, John Day 66 percent of average, Deschutes/Crooked 64 percent of average, Klamath 60 percent of average, Malheur 59 percent of average, and Lake 58 percent of average. On the west side of the Cascades, where you would expect to find much more snow on the ground, the percentages are catching up but still have a ways to go. The Hood River Basin is at 75 percent of average, Willamette 66 percent of average, and Rogue/Umpqua 66 percent of average.

Last year’s snowpack not only helped irrigators in the summer of 2008, it filled Oregon’s reservoirs with enough water to carry over into the next year. With an anticipated strong snowpack this winter, those reservoirs should be in great shape for the summer of 2009.

“It helps when you have back-to-back good years,” says Parsons. “We are set up to do well water-wise if we can keep the trend going.”

Last year, heavy rainfall produced flood events in western Oregon. Parsons says this winter’s overall precipitation, either in the form of snow or rain, should be above average but below last year’s amount. His earlier prediction of above normal snowfall in the lower elevations, including the Willamette Valley floor, has already come true.

Sub-freezing weather has hit Oregon this week and more is expected. Temperature forecasts suggest Oregonians should bundle up more often this winter and could impact agriculture depending on what commodity might be affected.

“Under our seasonal climate forecast model, there is an above average chance that the current bout of severe cold could last into January or a separate blast of cold weather could hit after the new year,” says Parsons.

It won’t be until April before officials can truly determine what kind of 2009 water year it will be. Also, Oregon’s diverse topography makes it hard to paint the entire state with one weather brush when it comes to forecasting winter weather. But at this point, with winter officially arriving this weekend, all signs point to another good year for those who depend on a strong supply of water.

Disclaimer: Articles featured on Oregon Report are the creation, responsibility and opinion of the authoring individual or organization which is featured at the top of every article.