Warmer in Seattle Than Los Angeles or San Diego!

A brief heatwave in the Northwest is ahead and it will flare up violently on Friday.

So be prepared with t-shirts, shorts, sunglasses and cool drinks. All the more jarring after an unseasonably cold spring.

Many of you will experience temperatures in the 80s….

Let me start with the predicted temperature for Friday at around 5pm on Friday according to the UW WRF model. The white areas are where temperatures are predicted to rise to 80F or more. Bright hot.

Temperatures will be cooler near Puget Sound and Northwest Washington. So if you like the heat, move inland and south. And cancel your trip to southern California – it will be warmer here!

Saturday will be a transition day, with cooler air starting to move inland on the coast. But it’s still coming in the mid-’70s in the interior west of Washington and Oregon. Expect further warming in the Columbia Basin, where mid-80s temperatures will be common (see forecast for Saturday 5pm below).

A most advanced approach to forecasting uses a high-resolution set of multiple forecast runs, each slightly different. Below are the predicted temperatures for the SeaTac from UW’s high-resolution aggregation system. Most modeling simulations will take place at 80-85F on Friday, which will be a record for that day. Same in Tri-Cities. Add 3-5 degrees to Portland.

The source of this warmth is a dramatic high ridge that will develop along the West Coast on Friday (see below). Such ridges are related to warm high-air air that gets even warmer as it rapidly sinks into the lower atmosphere (and thus warms by compression).

This high-altitude high pressure will cause the development of high pressure to our east, leading to an easterly (from the east) flow over the area (see sea-level pressure map, with low temperature and wind). The eastward flow will produce intense subsidence west of the Cascades and the Olympics will lead to significant compressive warming.

Temperatures should be warmest on the west side of the western slopes of the Cascades.

Warm air results in lower atmospheric pressure, known as a heat trough (shown in the surface map above). And the easterly current keeps the sea air cool.

A classic pattern in our local heatwave.

Enjoy.

___________________

The program and information of the Northwest Weather Conference is online. This meeting, which will take place May 12-13 in Seattle, is the key weather meeting of the year in the Northwest. We have a diverse and exciting agenda. The meeting is open to everyone and if you want to attend you must register (on the website).

We’ll also be hosting a party/chat at Ivar’s Salmon House on Friday, May 12. It’s a fun and hybrid (live and zoom) meetup.