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The Spokesman-Review Newspaper
Spokane, Washington  Est. May 19, 1883

Weathercatch: From snow shoveling to puddle jumping – what happened?

Jerry Schmidt works on a malfunctioning motor for his front-yard elf teeter-totter after a Friday morning snowfall covered the area near the corner of 39th Avenue and Havana Street.  (DAN PELLE/THE SPOKESMAN-REVIEW)
By Nic Loyd and Linda Weiford For The Spokesman-Review

December got off to a wet start, but for two different reasons. That’s why the region quickly shifted from a winter wonderland to a warm, breezy spate of unusually rainy weather.

Fittingly, the first storm arrived on Friday, Dec. 1, the first day of meteorological winter, with heavy snow falling in the Cascades and 3.5 inches in Spokane. It was caused by a garden-variety winter storm system that’s common this time of year. Then, right on its heels, came a cluster of storms produced by a series of atmospheric rivers that formed thousands of miles away in the Pacific Ocean.

An atmospheric river is a long, narrow plume of warm, moist air that’s typically channeled by winds toward the West Coast. Several thousand miles long, “they pick up water vapor from the warm, moist air of tropical regions and drop the water over land in cooler regions as rain or snow,” according to the National Oceanic and Atmospheric Administration.

Which is exactly what happened during the early morning hours of Saturday, when the first atmospheric river made landfall in Western Washington, moving inland and eventually making its way across the Cascades and into Eastern Washington. On that day, temperatures rose to 38 degrees in Spokane, turning a mix of snow and rain into straight rain. Winds kicked in as well, with sustained speeds reaching 22 mph and gusts at 31 mph.

After a brief break, another, more powerful atmospheric river arrived on Monday, delivering more rain, winds and still warmer temperatures to the Pacific Northwest. Portland reached a high of 67 degrees.

The system packed an especially big punch in Western Washington, with significant rainfall, gale-force winds off the coast near Anacortes, and avalanche warnings for Stevens and Snoqualmie passes.

The atmospheric river’s impact peaked on Tuesday, with more widespread rain and impressively warm temperatures for early December. Spokane and Pullman reached 52 degrees and Lewiston topped out at 61. Spokane received 0.56 inches of rain, Deer Park 1.3 inches and Olympia 2.96 inches.

Since then, the Inland Northwest has received intermittent rainfall and temperatures have remained unseasonably warm. But the atmospheric river is waning, and a change is underway Thursday. Expect cooling temperatures and less rainfall.

As for this weekend, we could see some rain or snow, with borderline temperatures and the potential for varying types of precipitation. The big surge, however, is behind us.

Nic Loyd is a meteorologist in Washington state. Linda Weiford is a writer in Moscow, Idaho, who’s also a weather geek.