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Drenching rain on tap as next system brings risk of landslides, urban flooding to Western Washington

SEATTLE — While there won’t be ice-coated roads or wind-driven power outages, the latest weather system will feature drenching rain that could result in shallow landslides and urban flooding.

Here’s how KIRO 7 Meteorologist Nick Allard says it will unfold.

Forecast

The wind will increase in the Cascade Foothills again on Wednesday night ahead of our next weather maker.

A large area of low pressure is pushing more atmospheric river moisture into California. That low will rotate around a wave that will move the atmospheric river into our area starting tonight.

Once it starts, we can expect rain to last through a good part of Friday, with Thursday being the heaviest rain day.

When the rain starts, it should start as snow in the mountains before snow levels rise to 6,000 feet or higher. In the North Cascades, there is a Winter Weather Advisory for as much as 10 inches of snow before it turns to rain.

In the lowlands, one to three inches of rain will fall in the Thursday-Friday timeframe, meaning some urban flooding is likely where rainwater cannot drain quickly enough. Also, given the recent wet weather, shallow landslide risk will increase starting late this week and continuing into the weekend.

On the Olympic Peninsula, lowland spots near the beaches will get 3 to 5 inches of rain with more in the Olympic Mountains.

The Skokomish River in Mason County will be in flood stage — as it has been for much of the last week — but the Cascade rivers — while running high — will probably only reach minor flood stage or stay below flood stage into the weekend. Any eastward shift of the projected band of heavy rain over the Olympic Peninsula would change that river flooding forecast.

By the weekend, rainfall amounts go back to more typical Western Washington rates, but cloudy skies with rain showers at times look to be a good bet. It will turn a little cooler late in the weekend and early next week with highs back in the upper 40s in Seattle by Sunday and Monday.

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