Hot temperatures likely next week

After a very warm May, the weather has changed for the first half of June with periods of cooler temperatures, rain showers, and thunderstorms. Computer models have remained fairly consistent over the past several days showing strong high pressure developing next week which could bring an extended period of much above normal temperatures. The latest image showing U.S. risk of hazardous temperatures says it all.

This experimental product from the Climate Prediction Center issued today (Jun 11th) shows a high risk (60%) of excessive heat across the Columbia Basin on June 19th and 20th, with a moderate risk (40%) over this same area June 21st and 22nd.  The remainder of Central and Eastern Washington is in a moderate risk June 19-22nd. 

But before the heat, let's talk about the weather this upcoming weekend and how quickly the weather pattern transitions next week.

Here is the pattern for Saturday and Sunday:

12z/June 11th GFS model forecast of 500mb heights and 700-500mb Relative Humidity (image) valid 5 PM PDT Saturday June 16

12z/June 11th GFS model forecast of 500mb heights and 700-500mb Relative Humidity (image) valid 5 PM PDT Sunday June 17

Not good if you have outdoor plans.  A low pressure system moves little, bringing the potential for showers each day and maybe even a few thunderstorms.  Previous model solutions were quicker to move the low out, but now the weekend looks showery.  Note the images above depict relative humidity with the green colors over our region indicating high values of moisture.

After that, models show a quick transition in the weather pattern. The low over Idaho takes a quick jaunt to the southwest, setting up off the California coast with strong high pressure over the Inland NW. 

12z/June 11th GFS model forecast of 500mb heights and 700-500mb Relative Humidity (image) valid 5 PM PDT WED June 20th.

This results in a hot/dry conditions over our region while the low off the California coast possibly draws in much needed precipitation into the southwest.  A large area of heat expands into much of the west as the image below shows.

12z/June 11th GFS model forecast of 500mb heights and 850 mb temperatures (image) valid 5 PM PDT WED June 20

The European model shows a similar pattern

00z/June 11th ECMWF model forecast of 500mb heights and 850 mb temperatures (image) valid 5 PM PDT WED June 20

How hot will it be?  Well it's too far out to narrow down the numbers, but 90s are a good bet for many valleys, possibly touching close to 100° in the hottest locations.  Note that this event is still 8-10 days out, and the details will probably change.  But, don't be surprised by an extended spell of heat starting around Tuesday, June 19th.