The fires in Four Mile Canyon continue to burn. The Colorado Department of Public Health and Environment issued a Wildfire Smoke Health Advisory for Boulder County from 4 PM (MST) Wednesday through 4 PM (MST) Thursday. Smoke is expected to affect Boulder, Larimer and Weld Counties. Clouds during today's Terra and Aqua overpasses did not allow an AOD retrieval from space. The left image below is a timeseries of the Boulder-Colorado University PM2.5 ground monitor showing, indicating the times when smoke has impacted the air quality in Boulder, Colorado. The Boulder webcam image (courtesy of boulderflatironcam.com) was taken at the time when the highest PM2.5 concentrations were recorded in Boulder. Smoke is visible near the mountains and over downtown Boulder.
Ozone concentrations (upper left image, animations are courtesy of Airnow.gov) were good throughout most of the country except in the Mid-Atlantic states, between 3:00 to 6:00 pm (EST, where Moderate AQI were recorded. PM2.5 concentrations (upper right image) were Moderate in the Mid-Atlantic states. Northerly drier (low humidity) airmass associated with a cold front moving over the region drop concentrations to Good AQI levels. The passage of this air mass over Baltimore is evident in today's lidar image (lower left image). There is less scattering of pollution particle (red to green counts below a 1.5 km) after 15:00 UTC (11:00 AM local time), and from the wind profiler (lower right image) timeseries one can see that this is coincidental with the time when winds shifted from the south-southwest to a northwestern direction.