Some scanners you can set the weather as a priority freq and it will check for the 1050 tone... I know that my 163/164 and 700 will do it that way... also my bubble pack GMRS radios that I use work like that as well...
You can also put most scanners into a WX standby mode, where you are not listening to the WX freq but it will open the squelch when it hears a 1050 tone. The FIPS code is encoded into the 1050 tone, and if you have one of the the FIPS programmed it will open the squelch...
http://www.weather.gov/nwr/And
http://www.weather.gov/mirs/public/prod ... s_list.htmThe best way to test what you are looking for is on WED at Noon... When the test the alert system...
I use a scanner I leave at home on WX stnadby when I am not using it, just in case... But I will admit I am using a $200 scanner in place of a $20 WX radio...