Mammatus clouds over Ant Flat

These mammatus clouds appeared over Ant Flat in July 2019. They are often associated with severe weather and thunderstorms. The long-term forecast for summer suggests thunderstorms with mostly dry lightning during July and August.

SALEM — The Oregon Department of Agriculture’s long-term summer forecast calls for a summer that will average out to be cool and moist, but still include a dry July and August.

The forecast, issued Thursday, June 18, says a relatively cool, wet September shifts the overall three-month prediction to a cool, moist average for the summer.

“One of the things that’s highlighted in the three-month forecast is dry lighting, especially in July and August, which of course is a fire hazard,” said Oregon Department of Forestry meteorologist Pete Parsons.

Parsons’ July forecast for northeast Oregon, including Wallowa, Union and Baker counties, calls for slightly above normal temperatures and slightly below normal precipitation. He noted that equatorial sea surface temperatures west of Peru have changed from warmer than normal to cooler than normal in the past few months.

“That means we’re going to see some changes in our weather, especially as we go into fall and winter,” Parsons said.

The shift toward cooler temperatures may be evident by mid-August, Parsons said, giving northeast Oregon an August with slightly cooler than normal temperatures, but only about 36% of normal precipitation.

“August looks as though it will be a very comfortable month,” he said.

September will bring a continued shift towards cool and wet.

“We have cold ocean temperatures, a strong jet stream and colder than normal temperatures in the upper atmosphere,” Parsons said. “So I have pretty high confidence that September will have below normal temperatures, and lots of precipitation.”

Parsons’ model, based upon weather during years when similar sea surface temperatures developed (1958-59) is calling for September temperatures in northeast Oregon to be 3.6 degrees below normal and precipitation to be 252% of normal. That differs significantly from National Oceanic and Atmospheric Center for Climate Prediction forecast that calls for a hot, dry September and is based on climate trends.

“Two different methods, two different predictions,” he said.

For winter, Parsons said, there’s a heightened chance of colder outbreaks and low-elevation snow.

“It’s probably going to be a snowy, cold winter,” he said.

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