The PSU Raman lidar has been used to observe and analyze various events involving the influence of the passage of meteorological fronts on air quality in the northeast region. One specific event of interest occurred on July 10,1999. During the course of this event, an increase in the concentration of ozone and particulate matter (PM) is observed ahead of a front. As the front enters the region from the Appalachians, a large accumulation of ozone and PM occurs during the afternoon. As the front approaches closer to the site, an increase in water vapor concentration is observed. The arrival of the front at about 0530 UTC is marked by wind gusts accompanying a significant gravity wave, which is evident in the water vapor concentration. With the incursion of the dry air mass by 1440 UTC, the water vapor concentration decreases rapidly to half of its original value. The Raman lidar is demonstrated as an effective tool for discerning the fine scale structure associated with frontal passage. Studies of these variations should be included to improve our understanding of sub-grid scale physics of frontal activity. This event serves as a good description for several cases where air pollution episodes are significantly influenced by frontal activity.