RED LODGE, Montana – Just three months ago, the Yellowstone region like most of the West was dragging through an extended snow drift in the mountains and wildfire scars in Red Lodge from a year ago when the area was hit by a 105-degree Fahrenheit heat and fire.
Rivers and creeks this week raged with much higher and faster water than even the rare benchmark 500-year flood. Weather-whiplashed residents and government officials raced to save homes, roads and businesses.
Most scientists have discovered that they have a long-term climate change with a switch from drought to deluge, scientists said.
It was a textbook case of “weather weirding,” said Red Lodge resident and National Snow and Ice Data Center deputy lead scientist Twila Moon. The challenge of cropping hair up in a sweat band and helping them out.
But these were unique conditions to the northern interior West, scientists say. Most of the West don’t have much snow and will keep struggling with drought.
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In the Yellowstone area, after a winter with light snow, it has accumulated a few months ago, wet and cold, likely due to the natural weather event. Tom Osborne, a hydrologist who has spent decades in the area, said Tom Osborne.
Things looked good. The drought wasn’t quite busted – in fact Thursday’s national drought monitor still puts 84% of Montana under unusually dry or full-fledged drought conditions – but it was better. Then came too much of a moist thing. Heavy rains poured in thanks to a water-laden atmosphere turbocharged by warmer than normal Pacific water. And when it poured, it melted. The equivalent of nine inches of rain flow down Montana mountain slopes in some places. Half or more was from the melting snow, scientists said.
All rivers and streams reacted the same: “They shot up to levels beyond anything ever recorded,” Osborne said. “Hydrologists know there is no greater cause of flooding in the West more than a rain-on-snow event.”
One gage on the Stillwater River near Absarokee, where Osborne lives, normally flows at 7,000 feet (2,100 meters) per second during a moderate flood and races at 12,400 feet per second in a 100-year flood, he said. A once-in-500-year flood would mean water raging at 14,400 feet per second. Preliminary numbers show that on Monday, it crested at 23,700 feet per second, the equivalent of stacking three moderate floods on top of each other, according to Osborne.
La Nina may have helped pack in more snow at Yellowstone
La Nina conditions occur when parts of the equatorial Pacific ocean cool, changing global weather patterns. While La Nina is dry out in the US Southwest, it may have helped pack more snow in Yellowstone’s mountain peaks, according to Upmanu Lall, the director of the Columbia Water Center at Columbia University.
And while Oregon, Washington, Idaho and Montana have bigger snowpacks from a cold, wet spring, southern areas that were extremely dry with anemic to missing late spring snows, said UCLA climate scientist and western weather expert Daniel Swain.
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Then the “atmospheric river” – a ship flowing regions in the sky that moved large amounts of water – entered the area and dumped rain on the snow at a time when the weather was warm. Swain said: That’s a small climate change connection, he said.
Over the long-term, climate change is reducing snowpack in the West, according to Guillaume Mauger, and research scientist at the University of Washington Climate Impacts Group.
“With climate change, we expect less snow and we expect the melt season to be shorter,” said Mauger.
But the spring did not follow that long-term pattern.
“What a wonderful combination of that high snowpack that got built up in April, May, together with this rainfall event and the warmer conditions,” they said. “That’s where the flooding is coming from.”
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They said the atmospheric river that brought moisture from the Pacific “is a little bit harder” to link to climate change.
La Nina may have played a role in several ways. While there have been La Ninas like this one throughout the past. That is a unique combination, ”Swain said. “We already know that La Nina increases the risk of floods in some places. It increases the amount of active weather in some places. And then you have warmer oceans and a warmer atmosphere that can supercharge those. ”
“So you really can’t just say it’s one thing or the other,” Swain said. “It really is a booth. It’s the natural and the unnatural together. ”
A year ago, Montana climate scientists created the Greater Yellowstone Climate Assessment and warned of rain-and-snow events like this, said co-lead author Cathy Whitlock, an Earth sciences professor at Montana State University.
But the real-life flooding disaster was far worse, they said.
“Who could predict houses going into the rivers and bridges being destroyed,” Whitlock said. “It’s so much worse than you imagine. And it’s partly because the infrastructure isn’t set up for extreme climate events. ”