"Perfect Storm" Rainfall Comes to the Northwest

It has happened multiple times this past year.   

After an extended dry period, the circulation pattern changes, bringing wet conditions that get us close to normal again.

This is going to happen again starting tomorrow. 

The predicted accumulated precipitation through Thursday afternoon will be substantial in the Cascades, and even eastern Washington will enjoy a general moistening. (see below)

Importantly, the precipitation will continue!  By Sunday afternoon (below), some locations in the Cascades will enjoy 2-4 inches.  This will cause rivers to substantially rise on both sides of the Cascades.

Temperatures will dramatically cool for the remainder of the week....with highs declining to around 60F over the western lowlands (see below).

Cool enough that snow will fall at higher elevations (see below)

The storage for the Yakima River basin has remained full (see below).  This wet/cool period will guarantee it remains high for the remainder of the month. 

River flows are below normal because of the lack of snowpack, but flows should be close to normal after mid to late June when reservoir releases are dominant.

The precipitation and relatively cool temperatures will ensure that soil moisture remains in good shape (currently, 78% of the area is adequate)--see below:

If any of you were considering planting seeds or plants, THIS IS THE TIME TO DO IT!  Soils have warmed, and precipitation will keep the ground moist.

Substantial Precipitation Will Soon Return to the Pacific Northwest

For those worried about Pacific Northwest drought, I have some news that should give them substantial comfort: substantial rain and snow will return to the Pacific, accompanied by cool temperatures.  

And not a hint of any heatwaves.  In fact, much cooler temperatures are expected.

So get your rain jacket out of the closet, get ready to plant some seeds,  and think about delaying that late-May hike.

Let's start with the best, the European Center model forecast for precipitation over the area (below).

The expected precipitation through Wednesday afternoon starts the wetting process:

By Sunday evening, all the mountains will be thoroughly moistened.  

But there is more!  By the morning of Monday, May 25, the totals are impressive, with some mountain locations exceeding 4 inches.  Even rain in eastern Washington.  This is serious precipitation.

Importantly, temperatures will cool substantially over the next week, so there will be substantial fresh snow in the Cascades (below).   Expect the % of normal snowpack to rise substantially from this late-season snow.

So what is going on?  

With the change in season and the transition from La Niña to El Nino, the upper- level pattern has unlocked, and some strong troughs of low pressure will be moving into the Northwest.  

To illustrate,  below is the forecast upper-level map for Friday morning.  An impressive trough of low pressure (blue colors) will build off our coast.

A week later, ANOTHER strong trough is forecast....winter-like in intensity in a similar position.

Other modeling systems (like the NOAA GFS) are doing similar things.   

Extremely favorable and well-timed for Northwest agriculture and local water resources.