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Monday, November 18, 2019  Spokane, Washington  Est. May 19, 1883
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News >  Spokane

The science behind the storm: How weather and timing wreaked havoc on Spokane

Ice clings to a tree leaves near a Maple Street on Wednesday, October 9, 2019, in Spokane. (Tyler Tjomsland / The Spokesman-Review)
Ice clings to a tree leaves near a Maple Street on Wednesday, October 9, 2019, in Spokane. (Tyler Tjomsland / The Spokesman-Review)

Branchstorm 2019. The perfect storm. Ice storm ’96 redux. Whatever you call it, the storm that walloped the Spokane region early Wednesday morning is one for the books – both history and science.

It was the earliest significant snowstorm on record for Spokane, and delivered a heavy and wet snow, perfect for sticking to all those leaves that hadn’t yet fallen from the branches. Altogether, what could have been a perfectly normal early winter storm wreaked havoc on a scale not seen since the ice storm of 1996 and 2015’s windstorm.

“If this snowstorm would’ve happened in early November, we wouldn’t have seen this. That was what made this so unique,” said Jon Fox, a meteorologist at the National Weather Service’s Spokane office. “It happened to be the perfect sort of storm. The right place at the right time.”

Weather forecasters knew something was coming, but were unsure of its trajectory. Originally, meteorologists predicted the system would move south of town, over the relatively treeless expanse of the Palouse. They saw a band of precipitation coming from the northwest and heading over the Columbia Basin generally following the path of Interstate 90. The low pressure system was wrapping up all the moisture it could as it moved.

“We were pretty confident we would get a deformation zone,” Fox said of the precipitation band. “But these things can be hard to predict. It just so happened it set up right over Spokane.”

Rain began to fall in Spokane around 8 p.m., and the temperature stood at 41 degrees. But as the storm settled over Spokane, cold air from the northeast blew in, and the system vacuumed it up. The wet air from the west and cold air from the east combined, and snow started to fall at 10:30 p.m. It was 34 degrees.

Going from rain to snow is another odd aspect of the storm. Snow frequently turns to rain, but rarely the other way around. That’s because colder air is usually dry. This cold air was wet, as the sheets of raining falling moments before attest.

By 11 p.m., temperatures hit freezing, 32 degrees, and snow continued to fall. Not only was it wet, it was heavy. One measurement meteorologists use is the snow-to-liquid ratio. Snow is usually around 13-to-1, meaning 0.13 of an inch of rain converts to 1 inch of snow.

“This one was 10-to-1 and less. That just means the snow was particularly heavy and wet,” Fox said. “It was raining so hard before it turned to snow.”

Shawn Bennett, a certified arborist and owner of Grace Tree Service in Coeur d’Alene, was in town for ice storm in 1996. He said this week’s storm reminded him of that one, primarily because of the tree destruction left in its wake.

The trees that suffered the most this year, he said, were deciduous and had yet to drop their foliage.

“It’s the leaf surface area,” Bennett said. “And they’re species of trees that had bad branch attachments. They’re reaching for light. Their limbs are 30 feet long. A big lever arm.”

In other words, the rain fell, and gathered on the broad leaves, at the end of the long branches. Then the snow fell, gathering on the puddles on those broad leaves. Then it all froze.

“That adds hundreds of pounds of weight,” Bennett said. “They broke to save themselves.”

It was around midnight when the steady snapping started echoing through Spokane’s deeply treed neighborhoods. A creaking preceded the snap, as branches bore their weight closer and closer to the ground. Then, a final pop and a deep thump marked the end, as the overburdened limbs slammed into the ground.

The last report of snow came at 3:13 a.m., and the clouds cleared out by 7. It was the earliest big snowfall in Spokane, besting the previous record of 5.9 inches that fell on Oct. 22, 1957. The earliest snowfall on record still belongs to Sept. 23, 1926, but only an inch fell then.

Kelly Chadwick, a certified arborist and owner of Spirit Pruners in Spokane, said the trees hit by this week’s storm stand in contrast to those felled by the windstorm four years ago. During that storm, which brought 71 mph winds to Spokane right as the sun was setting, pine trees and spruces came down. This time, virtually no conifers were damaged.

“They’re built to have their needles in the winter and carry this heavy load,” Chadwick said. The leafy deciduous trees that lost branches this week were “not used to having leaves on them when it snows.”

Chadwick blames global climate change. Fox, at the weather service, said he didn’t believe this storm was a sign of things to come, either for this winter or in years to come.

“I’ve been here well over 20 years and have never seen anything like it,” he said. “But I wouldn’t guarantee that just because we started out this way means the winter will be any worse than normal.”

Regardless, both Chadwick and Bennett placed an amount of blame on the lack of maintenance on Spokane’s urban forest.

Chadwick described it as “trees out of their element growing in an open situation, combined with bad pruning,” and noted that a tree can live for 150 years, leaving it at the mercy of “five different humans taking care of it.”

Bennett agreed.

“A lot of street trees are already big and overgrown,” he said. “Trees that have been taken care of are less likely to face this type of traumatic damage. Pruning does help.”

Still, Bennett acknowledged the damage was not really preventable. “This is an act of God. It’s not negligence. That’s what your homeowners insurance is for,” he said “They’re big and beautiful but come at a cost.”

Wordcount: 966
Tags: news, spokane

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