It never rains in California?

There is a well-known song about it never raining in southern California and during the next ten days folks might give that music a listen.  Why?  Because it won't be raining there any time soon.

Here is the NOAA/NWS GFS accumulated precipitation for the next tens days.
Washington get plenty, as does northern Oregon.  But virtually nothing over California, Nevada, and Arizona.

OK...that is only one run.  What about the 21 member ensemble of forecasts (called GEFS)?  Here they are in what is called a plume diagram....none of the members show rain!

So what is going on?   

A persistent area of high pressure will develop over and and west of California.

For example, here is the upper level (500 hPa) forecast for 10 PM Friday.   Nice ridge west of California, but not enough amplitude to keep the Northwest out of clouds and some rain (this is known as a dirty ridge by local meteorologists).

And here is the average anomaly from normal of the 21 ensemble forecasts for the same level, but for the 240 hr forecast---unbelievable, a big ridge over the western U.S. (red and orange show above average heights)

Mama Mia! This is one persistent ridge!  Not good for skiers in the Sierra, who have enjoyed substantial new snow during the last week.

Now some folks are claiming that such persistent high pressure areas have become more frequent or persistent in the West.  Some even have a name for it:
the Ridiculously Resilient Ridge (RRR).   And a few individuals are claiming that it is due to global warming.  OK, let's check out their claims:  is such a feature becoming more frequent or intense?

So what I did was to go to the wonderful NOAA ESRL web site and examined the average 500 hPa heights (same level as above) over the western U.S. (see the region selected below) for the last 70 years.

Below is the long-time series of the 500 hPa heights for November through February.   Quite a bit of ridging (high pressure) during the 2015-2016 winter, but little trend since the mid-1970s, when there was a major switch in sign of the Pacific Decadal Oscillation (the dominant mode of long-term natural variability over the eastern Pacific).

What about near-surface trends?  Here is the time series for 1000 hPa heights for November to February (essentially the same as sea level pressure).  No long-term trend.

You can do this exercise for different West Coast regions or seasons and you get the same answer (I have tried many combinations)....there is no long-term trend in West Coast high pressure during the past half century. 

We have an anomaly the next few weeks, but there is no reason to expect that is represents  a persistent feature of our future.