Fading curves taken in Morgantown upon the signal of KDKA in Pittsburgh show an increase of intensity after nightfall provided a cyclonic area covers both cities or lies to the north of Morgantown. If a high pressure area covers both cities the night intensity does not increase above the day intensity and may even fall below it. These observations are explained by the theory that the Kennelly-Heaviside (E) layer is found at night in cyclonic regions but is not present in anticyclones. This theory is strongly supported by recent experiments of Ranzi on 100-meter waves.