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Swollen rivers are likely, flooding less certain, says National Weather Service

Tue., March 15, 2011

The National Weather Service in Spokane on Monday said it foresees an average chance that streams and rivers will reach flood stage this spring as a result of a greater-than-normal snowpack.

Most of the region’s rivers are likely to swell to full bank, and some may flood depending on the amount of rain and snow that falls in coming weeks.

Smaller streams in Eastern Washington, including Latah Creek, Little Spokane River and Palouse River, may see higher flows by later this week.

Milder air and a series of storms are causing those rivers to fill to near capacity, forecaster Jeremy Wolf said on Monday. Lower elevation snowpack has been melting.

Wolf said the weather service is advising residents to prepare for potential stream rises and use caution when approaching rivers and creeks.

“Rivers are expected to respond to the wet conditions over the next several days, but flooding is not expected,” according to a weather service outlook issued Monday by hydrologist Katherine Rowden.

A La Niña weather pattern built the snowpack during November, and late winter storms have also contributed.

As spring progresses and snow begins to melt, several Inland Northwest rivers are likely to approach flood stage, including the Coeur d’Alene River at Cataldo, where it may rise to within a foot of flood stage. The St. Joe River at St. Maries should rise to less than a foot above flood stage.

Similarly, Pend Oreille Lake should rise to a foot below flood stage later in the spring. The Kettle River near Ferry, Wash., also is at risk of reaching flood stage.

The water equivalent in snowpacks across the region is running at 101 percent of normal on the Spokane River, 114 percent of normal on the upper and lower Clark Fork, 115 percent of normal on the Kootenai River, 93 percent of normal on the Salmon River and 103 percent on the lower Snake River drainage.

The east slopes of the Cascades have below-normal snowpack, which may limit irrigation water in places such as Yakima Valley, hydrologists said.

The lower Columbia Basin is also considered abnormally dry in the latest U.S. Drought Monitor, Rowden said.

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