Mysterious Ashy Rain Falls in Washington and Oregon

A mysterious substance locals are calling "milky rain" was found falling in parts of Washington and Oregon last Friday afternoon and into the night. Experts are now speculating about its origins while simultaneously reassuring locals that it's unlikely a threat to public health.

Emergency Management officials in Walla Walla County, Washington were the first to report this unusual rain, posting on their Facebook page that this "'white stuff' on vehicles" is very likely volcanic ash from Volcano Shiveluch in Kamchatka Krai, Russia.

They came to this conclusion after verifying that the volcano had spewed a 22,000-foot plume of ash late last month. They reported that it's likely that this ash was swept up into wind-ways and water-laden clouds heading east across the Pacific Ocean.

The nature of the rain and dust has yet to be scientifically investigated, but most experts are agreeing that it looks to consist of fine ash particulates.

Interestingly, that's not the only theory for this relatively harmless phenomenon.

The Spokesman Review, based out of Idaho, recently spoke with weather forecaster Mark Turner, who made the claim that the ash more likely came from the Mexican west coast after a small volcano near Colima, Mexico, erupted on Wednesday. The resulting ash cloud could have been picked up by a storm system heading north, only to be shed in rain droplets by the time it was over Spokane, Wash.

Others even suggested that the ash could have come from a massive seven-alarm fire which had occurred in Brooklyn, NY six days before.

"While many have speculated on the origins of the residue, the truth is that we really don't know where it came from," the US National Weather Service (NWS) team in Spokane reiterated Friday afternoon. (Scroll to read on...)

By Friday evening, the NWS team had even conducted an atmospheric flow investigation in an attempt to get to the bottom of a mystery that had captured many north-westerners' fascination.

"The program, called HYSPLIT (Hybrid Single Particle Lagrangian Integrated Trajectory) is a computer program that uses algorithms to try and simulate how pollutants in the ambient atmosphere disperse and, in some cases, how they react in the atmosphere," they explained on social media. "We usually run it from a point to try and see where a pollutant will travel to. In this case we ran it backwards to try and figure where a pollutant came from."

And while, because of a 150-hour limitation, they could not trace the ash all the way back to its origins, they did determine that it had in fact probably come gliding over the east Pacific in fast-moving mid- to high-altitude systems. You can see the mapped simulation for yourself here.

So what does that mean for these theories? It most strongly supports the Russian guess, but it's important to note that all three of the aforementioned sources would require ash to travel thousands upon thousands of miles. The Russian volcano in particular is an estimated 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 CNN's own meteorologist, Derek Van Dan, recently suggested that people should wait for chemical analyses to come back before drawing conclusions. These tests will at least reveal if the ash is indeed volcanic, or if the reality is that everyone has been looking in the wrong direction.

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