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.