California and Oregon Are Getting Our Rain: But That is OK

 There is always a yin and a yang in the weather.

Because of the structure and limited extent of weather systems, one area's precipitation bounty inevitably means less precipitation than normal for an adjacent region.

This is often true on the U.S. West Coast.  When California is wet, we tend to be dry and vice versa.

In April, such a reversal of fortune is occurring, with northern California and Oregon receiving above-normal amounts, and less than normal precipitation over Washington State.

Let's start with the current water year (October 1 to now) precipitation totals (the percentage of normal is shown).

Western Washington and the Cascades are in good shape, which is why our reservoirs are full.  Southern California has been wet.  But Northern California and much of Oregon have been drier than normal.

Climatologically, precipitation tends to shift north in the spring as the moisture-transporting jet stream moves northward, leading to a drying of California, while maintaining substantial precipitation in Washington State and British Columbia.

You can see this effect in the climatological precipitation maps for the region (below).

For January, substantial precipitation (dark blue color) extends from Washington State to Northern California and down the Sierra Nevada. Even Southern California gets a piece of the wet action.

But April is different, with far more precipitation falling over the Northwest than California, with profound drying over the southern portion of the state (see below).  In May, the California lack of precipitation is even more profound

But this year, something different is happening. 

The total precipitation forecast for the next 15 days (below) is for heavier-than-normal precipitation in California, with southern Oregon getting a substantial wet bounty as well.    Washington State will get some welcome precipitation as well, but the real action will be south of us.

The folks in LA and San Diego will be startled by all the rain, but the thorough wetting of California will greatly benefit the huge agriculture industry of the Golden State.  

What is going on?  

This is not climate change, but rather the development of anomalous upper-level lows that are heading into California.  

Below are predicted upper-level (500 hPa pressure, about 18,000 ft) maps, with blue showing troughs of low pressure (which are associated with precipitation).

11 AM Monday....a deep trough over northern California.

5 PM Saturday... another CA trough

Monday, May 4?   Another low-pressure area is heading to California.

Finally, although Washington State has a dry period ahead, we received substantial precipitation last night from a wet system that dropped very heavy precipitation exactly where we needed it:   on the eastern side of the Cascades and over the mountain barrier (see 24 hr below).   

Perfect for supporting agricultural needs over the Yakima Valley region.  

The weather gods are taking care of both California and our region.😊