Satellite pic shows incoming rain part of moisture plume stretching 6,000 miles to China

A plume of moisture stretches from the Pacific Northwest all the way back to southeastern China (Photo: Google Earth)

The source of the incoming rain this week in Western Washington is known as an "atmospheric river", but if you were to compare it to an actual river, this one would rival the Amazon!

Satellite imagery as of Monday evening showed the plume of moisture stretched from southern British Columbia all the way across the Pacific Ocean into southeastern China.

According to Google Earth -- that's a bit over 6,000 miles following along the plume's path. (The Amazon River is a paltry 4,300 miles long.)

Think of the "river" as a path of a long fire hose, with heavy rains accompanying wherever the river ends up. This particular river is expected to sag south into Western Washington on Tuesday, with a stronger punch of moisture inbound for Wednesday and Thursday. Rainfall totals in the lowlands of Western Washington are expected to range between 1-3 inches while closer to 5-7 inches are expected in the mountains, depending on where exactly this river sets up.

As long as the river keeps moving, it'll prevent heavy rains from falling over one particular spot for an extended period, but if the river stalls, it can lead to greater rainfall totals and flooding.

The river briefly sags south into Oregon and northern California toward the end of the week but reloads and returns to Western Washington over the weekend. Forecast models still are varying a bit on how long the river drenches the mountains but some scenarios could bring potential flooding to mountain-fed rivers by the weekend.

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