Short Warm Period Followed by Cool Wet Weather

We are about to warm up into the mid-80s this week in the west and 90s in eastern Washington, followed by a profound cool-down and plenty of precipitation.

Consider the latest predictions for temperature in Seattle and the Tri-Cities below.

Temperatures peak on Wednesday, before dropping off the proverbial cliff by the end of the week. 

Classic for our region, where cool ocean air is always close by.

You can see the predicted regional temperature evolution spatially below.

The forecast high temperatures for today are quite moderate over western Washington (highs in the 70s), while warmer temperatures are found in the Columbia Basin.

But by Tuesday (at 5 PM), the reds (80s) have spread into western Washington.   Still cool along the coast and over NW Washington.

But by Thursday, a radical cooling has occurred in the west, with temperatures only getting into the 60s over the lowlands.  Eastern Washington has also cooled.

The cause of this transition?   The approach of a strong upper level tough of low pressure (see forecast at 500 hPa, about 18,000 ft) below.   Wow.

Are you planning a hike after Thursday?   Bring some rain gear.

To illustrate our soggy future, below are the predicted precipitation totals through Sunday morning.  Yikes.  Several inches in the mountains.  Even eastern Washington gets wet!

The NOAA Extended (6-10 day forecast) is wetter than normal over our region (see below)

The timing of this precipitation, right before our dry season, is superb for providing soil moisture, filling reservoirs, and reducing wildfire threat.

The Current Status of the Most Important Water Source in the Northwest: The Columbia River

When it comes to our summer water supply, nothing is as important as the Columbia River.

It is the largest regional source of water for agriculture.

Its water is the largest source of power in the region.

Its water supports important salmon runs.  

And Columbia River water is used for drinking purposes in some communities.

This year, the water availability of the Columbia River should be very close to normal, with no hint of drought conditions.

Let's start at the water level of Lake Roosevelt behind Grand Coulee Dam on the Columbia River (below).   The blue color indicates this year's level, which is almost exactly at normal levels (red line).

 

Or we can look at the predicted water supply for April through September at Grand Coulee Dam, with the latest predictions on the right side.  The forecast is only slightly below normal (green line).    The water supply on the river looks quite adequate this summer.

The Columbia River is in good shape because precipitation over southern BC was near normal this year, and the snowpack in the Columbia headwaters is near normal (see below)

Also encouraging is the substantial precipitation predicted through July 4  over western Canada (see below).

As I have suggested in earlier blogs, there is little reason to talk about drought over the Pacific Northwest this year.