At night, radiational cooling occurs where that absorbed heat rises from the earth and goes straight up into the atmosphere to about 1-3 miles up to the higher areas of the troposphere. If the conditions are ripe, mainly during times of high humidity, the troposphere can act like a mirror, a sort of waveguide. Trops are more prevalent during the late night, early morning hours. Since the ducts are 3 to 4 miles above the earth, the line of sight can be roughly 100-500 miles around. If a stalled weather front occurs, that ducting can bring stations over 1000 miles away.
TV also can get into the act during trops.
Now, the fun part. E-Skip mainly occurs during times of high thunderstorm activity. The highly powerful electric activity of these thunderstorms has been linked to the occurrence of E-skip. In 1991, during a VERY powerful batch of T-storm activity in MY area, I was getting some very usual skip conditions. But you can get a hint of a chance that E-skip is going to occur.