The weather front that was moving into your area from the west created the situation. Occasionally when atmospheric conditions are just right, "tropospheric ducting" is formed. This is a temperature inversion effect created by a stable-high pressure system over oceans or very large lakes where a warm, moist air mass is sandwiched between two cool air masses. VHF and some UHF signals can be ducted through this conductive tunnel by bouncing off the dense air within the system to propagate waves for hundreds of miles. Think of it as mother nature's coaxial cable or waveguide. This effect is usually seen only during the warm weather months. UHF is defined as the range from 300 Mhz. to 3 Ghz., and along the shorlines of the Atlantic and Great Lakes, it is common to have this effect present several times each year where single repeaters and trunked 400, 700 and 800 Mhz. Public Safety, business and other radio systems in the frequency range hundreds of miles apart interfere with each other so severely that communications are all but impossible - lasting for minutes to several hours. This can be a very serious situation when a trunked system with the same control channel properties affects another system a couple hundred miles away. That is why it is essential to have a simplex backup plan in place during such events.