A Significant Atmospheric River Hits the Pacific Northwest

The first significant atmospheric river of autumn has arrived.  

The satellite imagery tonight is impressive.

For example, consider the water vapor image from the NOAA GOES-West satellite.  A magnificent moisture plume from the Central Pacific into our region.

Here is another.

The forecast of the transport of water vapor by the European Center model for tonight at 10 PM is shown below.  The atmospheric river is moving huge amounts of water vapor into the Pacific Northwest, with the center of the plume directed to the northern Olympics and southern Vancouver Island.

The plume of moisture will be forced to rise by our regional terrain, producing substantial windward precipitation.

Below is the prediction of the total precipitation through 5 AM Wednesday (from the European Center forecast).  Southern BC and northern WA get hit hard.

The UW, ultra-high-resolution forecast for the same period shows the details (below).

As much as 3-5 inches on the western slopes of the Olympics and central/northern Cascades. Substantial amounts reach the eastern slopes of the Cascades.  Nice rain shadow over central Puget Sound.  

 

I bet I can get away with biking to the UW tomorrow!

If you had refrained from watering your garden... go ahead.  Probably time to find your umbrella as well. September will end up with normal precipitation for most of the region.