Landslide Danger 'Extreme' In Local Areas, State Officials Warn

PUYALLUP, WA - A new forecast of shallow landslide risk shows that King and Pierce counties could be in for slides in the coming days.

The forecast indicates that landslide risk is "extreme" in Pierce County from Puyallup to Gig Harbor. At this level, the forecast indicates "landslide initiation is expected to be very frequent and widespread."

King County is also under threat, but at a slightly lower level. Landslide danger is "high" in western King County, from Auburn up through Renton and Seattle. On the east side of Lake Washington - including Bellevue, Mercer Island, and Issaquah - landslide risk is "moderate."

The Puget Sound area is getting hammered by a pineapple express, which will continue to bring rain to the region through Thursday. The National Weather Service has issued a flood watch for the region, which expires on Wednesday. In total, the system could drop as much as 5 inches in the Cascades this week, according to the National Weather Service.

In a special weather statement released Tuesday, the National Weather Service highlighted Wednesday and Thursday as the most likely for landslides.

"Continued wet weather over many weeks has kept the soils of western Washington near saturation. Periods of heavy rain are expected over the next several days that will add one to three inches of rain in the lowlands, especially from Clallam and Snohomish Counties southward. This amount of rain will put extra pressure on soil instability," the statement said. "Leading to an increased threat of landslides. Today through tonight, and even more so Wednesday into Thursday will be the times of the greatest threat."

The landslide forecast is only for "shallow" events, which includes surface slides. Deep landslides, like the one in Oso in 2014, are much less common and there is no forecast available.

Image via state Department of Natural Resources