I found this script online for weather announcements on asterisk. IDK much about AGI, but I just put it on my system, (on phreaknet, you can dial 8840565 to hear it, although you may have to use the 7921111 DISA) and it has been working. I even purchased an Axis A8004-ve and one of the things i did with it while experimenting was set the destination to the weather announcement. The script just announces information from an xml file from the weather.gov website.
weather announcement script Asterisk AGI : Free Download, Borrow, and Streaming : Internet Archive