Precipitation and Cooler Temperatures Return to the West Coast

The persistent ridge of high pressure over the western U.S., which brought generally dry conditions and less snowfall, is now history, with persistent low pressure and wet conditions taking its place.

Good news for those concerned about water resources in the West.

To get some perspective, the figure below shows the difference from normal precipitation over the past 90 days across the West Coast.

Near normal over much of western Washington and normal to wetter than normal over central and southern California.  But substantially drier than normal over western Oregon and northern CA.

A few days ago, the pattern shifted, and a plume of moisture moved into Oregon (see satellite image on Sunday)

The result has been healthy precipitation totals just where we needed them (see total for the past 48 hours below).   Some locations got more than 3 inches.

During the next week or so, one strong trough after another of low pressure will be moving into the West Coast, bringing rain and snow.

The maps below will show heights at 500 hPa (think of it as pressure at 18,000 ft) at various times during the next week or so.  Differences from normal are shown by colors (blue, lower than normal pressure, troughs;  red, higher than normal pressure, ridge).

Tomorrow at 4 PM.  Major trough to our south.

Next Monday, another strong trough of lower pressure

Thursday, 20 Feb.  ANOTHER strong trough

The Sunday after.....ANOTHER trough.

These troughs will bring a lot of water to the West Coast, with big stuff to our south, where they really need it. Only modest precipitation over Washington State.

Below is the UW model precipitation total through next Thursday.  Western Oregon and California will be sodden.   We will only get wet. Really heavy precipitation over the Sierra Nevada.

The latest NOAA Climate Prediction Center 8-14 day forecast is for cooler than normal and wetter than normal conditions over the western U.S 

It appears that this pattern shift has staying power, and the water/snow situation over the western U.S. should improve substantially during the next few weeks.

Misinformation in the Seattle TImes About Drought, Snowpack, and Climate Change

It is frustrating to read stories by the ClimateLab folks in the Seattle Times that are simply not true.

Another story was published yesterday that predicts a major drought year ahead due to poor snowpack.

A poor snowpack driven by climate change.

The problem:   their claims are easily shown to be false

The Truth

In December,  the region was hit by several strong atmospheric rivers that produced massive precipitation.  

Soils became saturated, rivers flooded, and all regional reservoirs were filled to above normal levels.

Atmospheric rivers are associated with warm conditions, thus working against snowpack accumulation.  And January was relatively dry and warm aloft due to high pressure aloft.

Consider the critically important Yakima River reservoir system.  

The heavy rain caused a huge increase in reservoir storage (blue line).  Higher than ANY TIME OF LAST YEAR and equivalent to early May levels in a normal year.

Yakima water storage will easily reach 1 million acre-feet just with rain and snow melt during the last month, resulting in a full reservoir system.

To provide 100% of the water requested, the Yakima System needs to deliver 2.3 million acre feet, with the remainder coming from melting snowpack AND late spring/early summer rainfall.  

We are only halfway through the snow accumulation season in the Cascades, and there is PLENTY of opportunity to gain much more snowpack.

Currently, the snowpack in the Yakima Basin is roughtly 48% of normal, and this percentage will only increase...and substantially.   

Even if there was no additional snow this year, just rain, one would expect about 750,000 acre-feet from melting the snow that is now on the ground.

So WITH NO SNOW, we would get to 1.75 million acres feet.   76% of normal.

Snowpack percentage of normal yesterday for the Yakima drainage.

But we are only about halfway through the snow accumulation season, and models are going for a cooler/snowier period ahead.  For example, the European Center model predicts lots of mountain snow through February 22:

Extended seasonal forecasts are for a wet spring with normal temperatures (see below).

That means plenty of snow.

Moving beyond the Yakima River situation, snowpack is above normal over the eastern slopes of the North Cascades, and the snowpack supporting the important Columbia Basin is normal (and the water level behind the Grand Coulee dam is above normal).  

Regional reservoirs are in very good shape.

No drought.

Even Worst

As bad as all the unsupportable Seattle Times claims of regional drought, there is clear misinformation about the cause of the lack of snow last month.

The Seattle Times claims it is because of warming due to climate change:

Substantial portions of the article push the global warming origin of the thin snowpack.

This is demonstrably untrue.

The last month was warm and dry because of the persistent ridge of high pressure over the region.  

The map below shows the anomaly (or difference) from normal of the heights (equivalent to pressure) at 500 hPa (about 18,000 ft).  

A very strong ridge of high pressure over the western U.S. and an intense trough (low pressure) over the eastern U.S.

This pattern suppressed snow over the Western U.S. and ENHANCED snow over the East.

Such patterns have little to do with global warming (there is a VERY large published literature on this).

The claim of the Seattle Times that our low snowpack is connected with global warming is simply false, with the impact of global warming on regional snow quite modest, something proven by the lack of downward trend in the observed Northwest snowpack over the past decades (see below, SWE is snow water equivalent, the amount of water in the snowpack).

The continued deceptive information from the Seattle Times on climate issues is very worrisome and shows the dangers of journalism funded by advocacy groups (the Seattle Times Climate Lab sponsors).