We expect the skies to clear by lunchtime on Wednesday.  Thursday will be a day when contrails or condensation trails will zig-zag across a blue canopy.  These trails form when hot, aerosol loaded aircraft-engine-air mixes with super cold air from the upper troposphere. Most contrails quickly disperse and disappear, transitioning to form cirrus clouds. This occurs when incoming sun-energy is absorbed and the clouds escape infrared heat from the earth. The International Journal of Climatology reports that contrails can affect cloudiness and potentially the climate. Conspiracy theorists contend that governments create the trails to control the climate.  Researchers examined data from World War II Allied bombing raids involving more than 1,000 sorties from 1943 to 1945. They also compared data on raid-free days and found that out of 20 raids, May 11, 1944 was the best case study. On that particular morning, 1,444 aircraft left airfields across southeast England into a clear sky. The contrails from these aircraft suppressed the morning temperature by one degree.