A Cool, Wet Spring Ahead

 It is time to reveal the future--or at least the best forecast of it.   

The coming month or so is probably going to be wetter and cooler than normal in the Pacific Northwest.   Snowpack will build in the mountains.  Our reservoirs will be topped off.  Worries about Northwest water supply and drought will fade, and I suspect the dryland farmers in eastern Washington will be relieved.

We are in a La Nina period, where the central and eastern tropical Pacific is cooler than normal, and the associated winters and springs tend to be cooler and wetter than normal.  

But there is more--something I have noticed over the years.  La Nina conditions tend to result in large ridges of high pressure over the eastern Pacific, as we have observed frequently during the past months (see example below for Sunday morning).  When the ridge is close to us, conditions tend to be cool and dry, but if it shifts a bit to the west, disturbances can move southward, providing showers and snow.  That is happening today, by the way.

Upper-level (500hPa) heights (like pressure) for last Sunday morning

But late in the winter, the northeast Pacific ridge generally weakens, allowing more precipitation into the Northwest.  So Northwest precipitation tends to be more frequent late in La Nina winters and during the subsequent springs.

And nearly all the forecast models are going for this during the next month or so.  A cool, wet early spring.

My favorite extended-period forecast model is run by the European Center and I will show you its long-term (46-day) forecast below (through April 22).

The forecast difference of temperature from normal is for colder temperatures than typical over the entire region. (blue indicates cooler than normal temps below)

Precipitation for the same period?  

Above normal for the mountains of the Northwest as well as southeast Washington (see below).  

Very good for dryland farmers in southeast Washington.  Their wheat will be very important considering what is occurring in Ukraine.   As in most La Nina years, California will be drier than normal.  Not so good.

The European Center model predicts large amounts of snow over the Northwest over the next 46 days (see below).  I suspect that on April 1st, the regional snowpack will be above normal.  That, coupled with the currently very well-stocked Northwest reservoirs, bodes well for water supplies this summer.

The European Model prediction is consistent with the forecasts of others.  For example, the U.S. Climate Prediction Center is predicting above-normal precipitation for the remainder of the month over our region.

What about the short-term forecast?   

We have some light showers today from a passing system, but the real action starts this weekend, with heavy precipitation and snow in the mountains.  

Below is the precipitation for the 72 hours ending 4 AM Tuesday.  Yikes!  Heavy rain (3 inches plus) from northwest California to southern BC.   Plenty in southeast Washington.

In short,  keep your umbrella and rain poncho handy.   If you are a skier, look forward to an extended season.  And if you are a farmer in eastern Washington, look forward to a better year than last year.