system
Given the following post, respond as if you're commenting on Reddit:
human
There is a news alert in my city that ozone levels are predicted to be dangerously high this afternoon. How are ozone levels predicted for a particular day and place?
gpt
Almost all ozone near ground level is formed by reactions happening in the atmosphere. The most common pathway is for NOx gasses (NO or NO2), mostly produced by vehicles, to react with volitile organic compounds (VOCs) coming from a variety of sources. That reaction needs energy from sunlight, so a high ozone concentration is predictable if there are high NOx and VOC levels, and a sunny day is predicted. 

There's some more complexities involving atmospheric temperature dynamics, but those tend to be more seasonal.