Harrisburg, PA – The Pennsylvania Department of Environmental Protection (DEP) and its regional air quality partnerships have forecast a Code Orange Air Quality Action Day for fine particulate matter (PM 2.5) on Friday, January 24, 2020, for the Susquehanna Valley (Cumberland, Dauphin, Lebanon, Lancaster, and York counties) and Lehigh Valley (Northampton, Berks, and Lehigh counties).
Meteorological conditions on January 24 will become very favorable for PM 2.5 to rise across areas of eastern Pennsylvania. A departing area of high pressure will provide very light winds across the region. These light winds in combination with warmer air building aloft will allow a strong inversion to form across areas just east of the Appalachian Mountains. As a result, the mixing of air near the surface will be limited, allowing the particles to become trapped near the surface and rise into the code ORANGE range. Air quality will improve greatly Friday night into Saturday as an approaching storm system from the west will increase the winds and rain chances across the region.
An air quality action day, which is determined based on the forecasted air quality index, means air pollutants are at unhealthy levels for vulnerable populations. On air quality action days, young children, the elderly, and those with respiratory problems, such as asthma, emphysema, and bronchitis, are especially vulnerable to the effects of air pollution and should limit outdoor activities.