Ozone will reach the Unhealthy for Sensitive Groups (USG) AQI range on Thursday with stronger transport of polluted air from Southern California and a mostly clear sky. This pattern is due to the coastal low pressure system moving into the western US, replacing the high pressure area that persisted recently. Ozone will return to the Moderate AQI range on Friday as the low pressure system weakens, changing the regional airflow pattern. AQI is EPA's Air Quality Index - information is on EPA AirNow and the DAQ web pages.
-- You can follow Clark County air quality conditions and updates on Twitter: @CCAirQuality.