Ice Storm Largely Bypasses South County
While much of South Spokane was crippled by last week’s ice storm, some outlying areas to the south and southwest of the city escaped relatively unscathed.
The worst of the freezing rain stayed along the Spokane River Valley and areas to the north.
Little of the frigid air that froze raindrops to the trees in Spokane penetrated beyond the hills to the south and west of downtown.
“We got a little bit of snow,” said Mayor John Logan in Spangle, where power went out for about two hours on Nov. 19.
In Cheney, the freezing rain fell for about an hour and helped weigh down snow-laden branches, but power in the city was lost for only 18 minutes.
Professor Bob Quinn, who teaches geography at Eastern Washington University, said the dramatic difference was caused by differences in air layers within the storm.
Freezing rain, when it occurs, usually shows up in a narrow band between cold and warmer air masses. That was the case in Spokane last week.
Arctic air from the Yukon was brought into southern British Columbia by a low pressure area over Vancouver Island.
While the cold wasn’t the numbing, below-zero type that strikes the Inland Northwest at times, it was still subfreezing.
At the same time, a storm laden with mild rain moved ashore in Northern California and Southern Oregon, where precipitation at one location measured more than 6 inches in 24 hours.
That moisture was driven northward on upper level winds blowing from the southwest.
A surface low pressure that passed over Lewiston caused the arctic air to be drawn down the mountain valley that runs from Bonners Ferry to Sandpoint to Rathdrum and Post Falls. From there, the cold spilled into Spokane.
So the air Tuesday over Spokane was freezing cold up to a level of about 1,000 feet above the ground. From there, the air was above freezing to an elevation of 8,200 feet.
The cold on the ground caused the rain from the mild air above to freeze on trees and power lines.
But the layer of cold air wasn’t strong enough or thick enough to spill over the South Hill or the Sunset Hill to the west.
As a result, snow and rain were reported south of Spokane, but not freezing rain.
“That’s the way ice storms behave,” said Quinn.