Date: Thursday, July 19, 2018
Action Day? No
Thursday will be a very comfortable mid-summer day across the State of Delaware. Nearby high pressure will promote mostly sunny skies, seasonable
temperatures, and very light to calm surface winds. Converging surface winds will concentrate pollutants, allowing ozone to rise into the Moderate
range, with the highest ozone expected in northern Delaware. A very clean regional and upwind air mass should prevent ozone from rising too quickly
on Thursday. Particles will remain in the Good range in response to low atmospheric humidity.
More typical summer conditions will return on Friday as humidity begins to rise. Calm/light surface winds overnight and into the late morning will give
way to breezy southeasterly winds in the afternoon. Localized transport of pollutants and mostly sunny skies will allow for some ozone formation to take
place before surface winds are able to shift fully onshore and bring cleaner air into the state, allowing daily average ozone to remain in the Moderate
range. Particles will increase due to rising humidity but remain in the Good range. A coastal low pressure system will lift northward along the Atlantic
coast on Saturday, bringing mostly cloudy skies and scattered precipitation to the state. Gusty easterly surface winds and strong onshore (clean) flow
aloft will ensure Good ozone and particle air quality.