Will the Northwest Have Enough Water This Summer and Fall?

There is been a lot of talk about the huge amount of snow and rain hitting California, where the drought of the previous few years is now clearly over.

But with the bulk of precipitation heading south of the Northwest during the past month or so, where does that leave the Pacific Northwest?    How is our snowpack doing?  Are our reservoirs filling?  Are we in water trouble?

It is time to check this out, particularly as we are moving into the drier Northwest spring.

The bottom line:  Washington State water storage is modestly below normal, with no serious water issues expected.

First, the snowpack.   Oregon snowpack is well above normal and Washington State snowpack is generally near normal, although a bit below normal for the Yakima Basin and the North Cascades.

Precipitation

 With the "meteorological hose" heading in California (and after the uber-dry period during fall), the Northwest has been drier than normal.   To illustrate this, below is the percent of normal precipitation during the "water year" starting on October 1. 

The Northwest has gotten about 70% of normal precipitation during this water year, with the eastern slopes of the Cascades being a bit above normal.    

Why wetter than normal there?  Because with persistent low-pressure areas of the coast, there has been enhanced easterly (from the east) flow.  Such flow is upslope on the eastern side of the Cascades, producing more precipitation!

Reservoir Levels

       Let's start with the Seattle reservoir system.  As of March 6th, reservoir storage is modestly below normal (around 90% of normal).

The snowpack above Seattle's reservoirs is slightly above normal 

The bottom line is that Seattle is in in decent shape and the persistent cool temperatures should help maintain the snowpack into spring.

Next, let's turn to the Yakima River reservoir system, which is very important for agriculture over eastern Washington (see below).  It is also below normal (roughly 85% of normal).

To get a broader view, below is the Water Supply Forecast for this summer from the NOAA River Forecast Center.  Near normal (green) for western Washington and northwest Oregon, as well as southeast Washington and much of Idaho.

But modestly below normal over the eastern slopes of the Cascades and the Okanogan region.

Now let me note that earlier this winter, my profession was calling for a cool/wet winter because of La Nina.  We got the cool, but not the wet.  We also thought California would be drier than normal.   

We have a ways to go on seasonal prediction 😊

Looking Forward

La Nina is now collapsing as is its impact on global weather systems.  

So what does the latest model forecasts indicate?

For the next two weeks, the European Center ensemble system of many forecasts suggests a continuation of generally wet to the south and dry over northern Washington and southern BC. (green and blue indicate above normal, you can guess what brown is)

Temperatures?  Disappointedly no warm-up for the heat-starved residents of the Northwest (see the prediction for the next 10 days below)

Admission: I bought a new jacket this morning.

In summary, we have been cool and relatively dry this winter as a result of a persistent atmospheric pattern with the jet stream heading south into California.  Our water situation is a bit below normal but nothing serious, well within the normal variability.

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The Pacific Northwest Weather Workshop is the region's premium weather gathering, and it is back as an in-person meeting on May 12-13th at NOAA's Sand Point facility in Seattle.  This will be a hybrid meeting, so those of you who wish to attend remotely can do that as well.

At this workshop, we discuss the latest advances and studies regarding Northwest meteorology and climate (including British Columbia) and review the major weather events of the past year.

The upcoming meeting will include talks on advances in regional weather prediction technology, the Portland snow bust, the December ice storm, wildfire meteorology, the autumn smoke event, new initiatives in media weather, regional climate change, and much more.

We will also have a banquet at Ivar's Salmon House (in Seattle) on Friday evening, with an engaging speaker.

If you are interested in attending, you can get more information and register at the meeting website:

https://a.atmos.washington.edu/pnww/

And those interested in giving a talk, please send me a title and abstract by April 10.