Large contrasts in temperature and pressure will develop throughout the falls. But there is no rain

Next week, incredible weather contrasts will develop across the Cascades.

Cold Arctic air will spill into the Columbia Basin, topped by low clouds. tthe temperature there will drop to single digits and the sea level pressure will be very high due to the dense cold air.

In contrast, although slightly cooler than usual, temperatures in the western lowlands will reach over 30 degrees Celsius. But downstream (west) of gaps in the terrain (such as the Canyons) Columbia River) VERY strong winds will pound localized areas to the west.

To illustrate, here are forecast temperatures for Seattle and Richland for the next week or so from a combination of National Weather Service forecast models.

In Seattle, the low 40s high will dominate through Friday, followed by a drop to the upper 30s. Freezing temperatures at night.

Cold but bearable.

But consider Richland in the Tri-Cities.

By the end of next week, the highs will only rise to around 20F and the lows will drop to single digits. The coldest spots east of WA will drop below zero degrees.

Cold, dense air east of Washington will lead to the development of high pressure in the Columbia Basin. Below is the forecast for sea level pressure (solid line) and low temperatures (colors, blue and purple are the coldest) for Thursday afternoon.

You notice a sharp pressure change (slope) over the Falls. Large pressure changes lead to wind. By the end of next week, very strong easterly winds will develop in the passes and in the Canyon (more than 60 mph).

Through Wednesday, December 21, extreme cold will hit eastern Washington, with morning temperatures 30 to 40 degrees lower than usual (the forecast map below shows the difference from average temperatures). normal surface air). Temperatures of 13F are mildly below normal in western Washington.

And this model will dry. What are the causes?

Our old friend this fall: a strong upper-level high pressure band in the northeast Pacific, with a strong northwesterly current to its east (see below late on Thursday). Five)

This stream from the northwest will carry very cold air southeast of the Rockies, and a severe portion of it will enter eastern Washington. But no rain.

To really impress you, here’s a map of the temperature, wind, and altitude forecast at 850 hPa (about 5000 ft) for Sunday night. Purple is very cold, and white is very, very cold. I don’t want to be in central or eastern Montana.

A very suitable way to start the winter.