UPDATE: 'Milky Rain' Not Volcanic Ash, Says Researcher

Remember that mysterious "milky rain" that fell in parts of Washington and Oregon last week? Now a researcher from Washington State University (WSU) is making the claim that it is not volcanic ash caught in rainclouds, as was suspected, but rather the result of a rare event at an ancient lake.

The rain, which fell on Friday, was turning rain gauges a murky white and splattering car hoods with a chalk-like residue. Even without a chemical analysis, experts quickly deduced that the unusual rain was harmless. What's more, they speculated that its origins could likely be traced back to clouds of volcanic ash which came from either a recent eruption along Mexico's west coast, or from the volcano Shiveluch in Kamchatka Krai, Russia.

However, when the US National Weather Service (NWS) team in Spokane, Wash. ran a series of simulations to predict local storm patterns and atmospheric trends, it remained unclear if the ash had come from either of these sources, as high-speed winds had moved in a deep 'U' up and down the far-eastern Pacific. What's more, the two most likely sources for volcanic ash were up to 4,000 miles away.

According to the US Geological Survey, an explosion at Washington's own Mount St. Helens on May 18, 1980, one of the best monitored volcanic eruptions in history, spewed trace amounts of ash only as far as Colorado and Oklahoma - 1,000 and 1,500 miles away, respectively.

That's why WSU meteorologist Nic Loyd suspects that experts should abandon the volcanic ash theory altogether.

"Drifting ash from a volcanic eruption would have been easier to figure out," he said in a statement, arguing that as the origins are still unclear, the cause is likely something more complex.

Loyd and his colleagues at the AgWeatherNet service believe that the "ash" is actually dust from a dust storm that struck Summer Lake in central Oregon on Thursday night. The storm clocked up to 60 mph winds, and combined with an unusual progression of weather events to push the dust northward. (Scroll to read on...)

First, Loyd explained, hurricane-force winds whipped across the Summer Lake region in south central Oregon, "lofting dry, light-colored sands and soils into the air."

Next, strong southerly winds transported the sand and soil particles northward.

"Had the winds not been so strong or constant, the dust plume would have dispersed before it got [to Washington]," said Loyd. "As it was, it was able to travel a large distance in less than 12 hours."

In the midst of a northbound rainstorm from the Pacific, Washington residents didn't even notice when the dust arrived, as it was immediately caught in falling raindrops to create the phenomenon that had captured the West Coast's attention last week. That storm eventually moved onward towards Oregon, carrying what remained of the dust with it - and speckling car hoods with mystery in the process.

"It was an unusual convergence of weather factors that set up the event," Loyd concluded.

Still, it should be said that while this is likely the most convincing and thought-out theory yet, it will take chemical analyses of the "milky rain" to show what really happened once and for all.

Who knows? Maybe it was actually raining milk! I can't wait for the cookie hail next.

For more great nature science stories and general news, please visit our sister site, Headlines and Global News (HNGN).

- follow Brian on Twitter @BS_ButNoBS.