River Flooding Begins & Another Atmospheric River Starting Saturday Evening

FastCast—Saturday, Nov. 13 to Monday, Nov. 15:

River flooding has begun on rivers around the region as the atmospheric river moves out. Most areas south of Seattle received 1-3.5” of rain from Thursday to Friday afternoon. See the blog below for more information on river flooding. Expect a break in the rain through Saturday evening. Saturday will be mostly cloudy with highs in the upper 40s to low 50s. As if we haven’t already had enough rain…atmospheric river #2 arrives late Saturday. Rain will begin Saturday evening, continuing on and off at times through Monday evening. Uncertainty remains regarding total rain amounts for this next atmospheric river, but totals will be highest in the North Interior (Skagit County northward). Totals of 1-3 inches are expected in the metro area, with much more in the mountains. It will be breezy to windy (30-40 mph) at times, and temperatures will rise to the upper 50s to low 60s from late Saturday night to Monday afternoon. 

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Continue reading the full blog below!

It has been a very wet past 2 days in Western Washington, as the first of two atmospheric rivers moved through the area. Heavy rain contributed to urban flooding and flooding on many rivers that flow off the Cascades. Below is a photo of the Carbon River at Fairfax on Friday afternoon, taken by Bonney Lake Weather on Friday afternoon.

The water was moving very fast, and logs were floating in the swift current. This was a common scene around the region on Friday, and river flooding will continue through Saturday, rivers will briefly recede, and many (but not all) will rise again by late Sunday.

Below are rain totals from Thursday morning to Friday afternoon. 

Totals varied around the area. From approximately Seattle southward, totals ranged from 1.5 to 3.4 inches. North of Seattle, totals were 0.75 to 2 inches. In the mountains, totals of 4.5 to 6.7 inches were recorded, which coupled with snow levels around 10,000 feet, caused all the river flooding.

Now, a look ahead to atmospheric river #2…there is uncertainty regarding where the heaviest rain will fall. This depends on where the heaviest plume of moisture sets up. Forecasts should come in to more agreement by late Saturday. However, it does seem likely that areas from approximately Skagit County northward and in the mountains will receive the most rain. The uncertainty is in how much rain will fall in the metro area. Below is the atmospheric river forecast for 3 AM Monday.

This is a classic Pineapple Express setup, and relatively the same impacts are expected as in the previous atmospheric river, so stay tuned for more information.

One additional impact with this atmospheric river is the potential for gusty winds up to 30-40 mph (locally higher at times) from late Saturday to Monday evening. 

In short: more rainy & windy weather, river flooding, and potential urban flooding is in the forecast. Stay tuned for an update by 10 PM Saturday.