Dust particle precipitation

The "milky" rain that covered the region last Friday was most likely just dust-filled drops.

According to Greg Koch, forecaster at the National Weather Service in Spokane, the most plausible explanation for the wacky weather was dust storms in Oregon, particularly on the seasonally dry Summer Lake.

"Preliminarily, we thought it might have been dust coming out of northwest Nevada," Koch said Wednesday afternoon. "After doing a little more digging on Monday, there were spotter reports of blowing dust in south-central Oregon."

Both Nevada and Oregon experienced mighty gusts for several hours Thursday night into Friday morning. The NWS office in Reno documented speeds as fast as 134 miles per hour, but mostly remaining within the 50-90 mph range.

"There was dust blowing around all over," Koch said. "That whole region has experienced a multi-year drought. It's dusty, and some of those lake beds are pretty dry."

The Press reported on the anomaly, which generated plenty of conversation in the community and had weather officials scratching their heads.

"We really don't know what it was," Mark Turner, observing program leader at the Spokane NWS office, said in Saturday's Press article. "We don't really have a hypothesis either."

The cloudy, whitish rain fell throughout the Inland Northwest, with reports of hanging dust (which looked like fog in some areas) and photos coming from Hermiston through the Tri-Cities to Spokane and Coeur d'Alene.

"I saw it as unusual," Koch said. "It was a different color than normal, and it was in a pretty high concentration."

One theory is that it could be volcanic ash from Russia or Japan, but Koch said if the Inland Northwest received ash from overseas, Seattle and Portland would have experienced it too.

"It was a very narrow corridor, if you look at our map," he said. He explained that the dust in dry lake beds in that area, such as Summer Lake, is generally white or gray.

"I would concur with the NWS," said John Abatzoglou, assistant geography professor at the University of Idaho. "It looks like dust from the playa over southeast Oregon was picked up by some very strong southerly winds that accompanied the weather system late Thursday and into Friday. While such precipitation events are not unusual for this time of the year, the combination of the lack of snow cover and dry conditions in southeast Oregon was probably key to having muddy waters fall from the sky."

Graphs on the Inland Northwest Weather Blog, www.inlandnorthwestweather.blogspot.com, illustrate just how dust could travel more than 500 miles in a relatively short amount of time.

"The soil that we're standing on where we live here, at least a good portion of it, came from somewhere else," Koch said. "Mother Nature shifts our soils around, whether it be by wind, or rain or floods. That erosion process is very natural."