PHILADELPHIA, PA — It is rare to have an ozone action day in Philadelphia in December, but that is the status for December 4, 2013. (source)
Data courtesy of: Pennsylvania Department of Environmental Protection
What does this mean to you? If you live within the Greater Philadelphia Region, DO NOT BREATH. Breathing may be hazardous to your health.
-
An Ozone Action Day, which can be declared by a local municipality, county or state, is observed at certain times during the summer months, when weather conditions run the risk of causing health problems. …
Forecast Discussion: Wednesday will be an Air Quality Action Day for the Philadelphia metropolitan region. It will be unseasonably warm. Rising atmospheric humidity, with partly cloudy skies, will promote particle formation. Stagnation overnight and through the morning rush hour provided by calm winds and a shallow boundary layer will allow pollutants to accumulate. Surface winds from the south/southeast will pick up in the afternoon, but they will be insufficient to adequately ventilate the atmosphere. As a result, particle concentrations will average in the low Code Orange range. Extended Forecast: A slow-moving cold front will approach from the west on Thursday. Unseasonably warm and humid conditions will continue. Stronger south/southwesterly winds in the afternoon ahead of the front will provide enough ventilation to drop particle concentrations into the Moderate range. Particle concentrations will decrease further on Friday but remain in the Moderate range as the air mass is slow to change behind the frontal passage. -Huff