Do you know about XM Channel 214 - Washington? The XM Weather and Traffic Station for the Washington DC area.
Through an agreement between XM and several local counties, Emergency Alerts will also be broadcast on this channel.
XM Channel 247 is also worth checking out as well, as a way to find out about larger scale emergencies and emergency messages from across the country. Additional information on that channel can be found here: http://www.xmradio.com/onxm/channelpage.xmc?ch=247
Did you ever wonder what other jurisdictions across the United States are doing? Check out this website: http://www.cybertelecom.org/security/eas.htm