Wet, Cool Weather Ahead for Much of the West Coast

 Generally, April is a month of rapid drying over much of California....but not this year.

A pattern that brings a series of low-pressure systems to California will be the rule for much of the month.

Let me illustrate by showing you a series of upper-level (500 hPa pressure, about 18,000 ft) maps.  Blue colors indicate much lower than normal heights/pressures.

Thursday evening, a strong low center will be parked off California, bringing a moisture flow into central and southern California

Saturday will bring a stronger low to Northern California.

This pattern will not go away.....a week later (Sunday, April 19) another strong low will be offshore the CA/OR border.

This series of troughs/low-pressure systems will bring bountiful precipitation to the West Coast.

Over the next ten days, substantial precipitation is expected over California and southern Oregon (see below), locations where the snowfall has been below normal.    This precipitation will top off reservoirs and ensure good river flow this month.

The predicted total snowfall for the same period is substantial, with large amounts in the Sierra Nevada.

One should note that the substantial precipitation this winter has filled California reservoirs, many approaching full (see below).  Right now, CA reservoirs are about 120% of normal. 

As noted earlier, the snowpack is substantially below normal (see below), savaged by the recent warm/dry period.  Thankfully, California has a massive water storage capacity.

The above-normal water storage in reservoirs will buffer the low snowpack, while rain this month will moisten soils going into the dry season.  This is important considering the drying effects of the recent warm/dry weather over California.