NOAA has some good info on this link.http://www.weather.gov/emwin/index.htm
You might also check around and see if anyone is rebroadcasting on VHF in your area. The NWS recently authorized rebroadcasting on about 5 of their VHF frequencies. The OEM of the county south of me (Will County Illinois) reboadcasts on 163.325 Mhz. Much more convenient than an satellite downlink.