The Pacific Northwest has been under a strong high-pressure system which has brought several days with stagnant air, which has led to poor air quality from northern California through western Washington. How much longer until the air gets moving again?

Good question! First, we must give a brief explainer on high-pressure systems. High-pressure systems produce sinking air. When the high pressure is in the mid to upper levels of the atmosphere, and the weather patterns are not moving much, then we call this a blocking in the atmosphere. This blocking causes the high to sit over the same region, usually for days and sometimes up to a week or a bit longer.

The sinking air also causes the temperatures to warm. During the summer months, this is when extremely hot temperatures occur. This is just what happened in the Pacific Northwest in summer 2021, sending hundreds to emergency rooms due to heat exhaustion.

In the winter, warmer temperatures than average also happen but of course, due to the winter, no one is sent to the E.R. Like in the summer, sinking air also limits the wind speeds in the winter, making the air stagnant. With the air not moving much, bad air quality alerts get triggered.

As the air is not mixing near the surface, contamination becomes a big problem, especially in cities where air pollution, due to power plants, or lots of traffic, tends to be a frequent problem. Those people with respiratory problems, such as asthma, are the most at risk. Often burn bans are put in place in cities to help limit the harm in local air quality.

The high-pressure system, which has been centered near the Pacific Northwest, will get moving and lose its punch by the weekend. With this setup moving, the next storm will arrive by the beginning of February. Cooler air and stronger winds are in the forecast by Monday morning, but for cities like Seattle, the rain arrives by Saturday evening and continues through the beginning of next week.

In fact, the climate outlook shows a total flip, for the first two weeks of February, with below-average temperatures for much of the West and below normal temperatures for the eastern half of the U.S.