Poor air quality continues to be an issue across the Pacific Northwest today. AIRNow AQI measurements peaked in Oregon and northern California in the Code Red (Unhealthy) range, with scattered Code Orange and Yellow (Unhealthy for Sensitive Groups and Moderate) observed at surrounding locations. In addition, Code Yellow AQI were experienced across the Central Plains, Great Lakes, Southeast through Northeast states. The widespread, powerful, high pressure regime impacting the Northwest on Monday plague the region, motivating air stagnation and little vertical mixing in the planetary boundary layer. This weather pattern is favorable for little particle dispersion near the surface, allowing particulates to accumulate, and is likely driving the poor air quality event. High pressure is forecast to continue to be in control across the Northwest until the weekend. Hourly weather observations in Redding, CA demonstrate clear skies and calm wind wind conditions, driven by the locked in High pressure pattern, throughout the entire day. Although PM2.5 levels were elevated in this region, there was no indication of raised aerosol optical depth measurements throughout the poor air quality region.