The Summer's Second Heatwave Comes Into Focus (And Slightly Cooler Than Initially Predicted)

As we get closer to the heatwave event, our more potent tools (like high-resolution ensembles of many forecasts) become available.  

And the latest information suggests that this week's heatwave will be a bit less intense than initially predicted.  And FAR less threatening than the June event.  

In the June event, everything came together to produce a "black swan" severe event.  Record ridge of high pressure, approaching trough of low pressure, strong offshore flow, and the occurrence when the sun was near maximum.  None of these ingredients will be present this week.

The National Weather Service has an excessive heat warning for a significant portion of the region (red colors below).

Bottom line:  a typical heatwave for the region.  I suspect there won't be any attribution reports for it.

The Forecast

The most powerful tool available to local meteorologists is the UW high-resolution multi-forecast (ensemble) system, which only goes out 72 hours.

Below is its forecast for SeaTac.  Today will get to around 86F.  But tonight will drop into the mid-60s, so with a fan you can cool down your apartment or house.  Tomorrow (Thursday) will see lower 90s, with a few degree uncertainty. Thursday night/Friday morning will cool to the 60s. Friday will be a touch warmer, reaching about 95F.  Although not shown, Saturday will be cooler and Sunday MUCH cooler

Portland is bit warmer (see below), getting near 99 F today and low hundreds tomorrow..but note the uncertainty of several degrees.  Slightly cooler on Friday.  Minimum temperatures are warmer there...in the low 70s Friday morning.  The Willamette Valley lacks the cool water enjoyed by western WA.

Eastern Washington (Pasco) will be around 105 F each day, perhaps a few degrees warmer on Friday.   Agricultural workers should be protected during the heat of the day.

Some locations in the Northwest may break daily records, but nothing more serious than that.

Next, let me show you the high-resolution forecast maps for 5 PM each day, near the time of highest temperatures.  

Today, temperatures will be moderate on the coast and Northwest Washington, mid-80s over Puget Sound country, upper 90s  in the Willamette Valley, and a bit over 104F in the lower Columbia Basin. 

Slightly warmer on Thursday, particularly over southwest Washington and in the Fraser River Valley.  I never appreciated how warm the exit (western) region of the Fraser River can be.

Friday will be modestly warmer in the lower Columbia Basin, but similar west of the Cascade crest.

And as mentioned above, a step down on Saturday and far cooler on Sunday.  

A typical Northwest summer heatwave.  I hate to think what some local newspapers will be saying about it.....😊😊