Here are a couple of more links about NAWAS. It is a very interesting system to listen to, especially during bad weather. This would also be a good frequency to montior during a disaster.
http://www.nebema.org/content/operations/ESF02.pdf
(NAWAS info begins on page 17)
http://www.fema.gov/pdf/library/1550_2.pdf
(More info than you would ever want to know about NAWAS)
For the most part, NAWAS is a telephone based communication system. However there are several radio links to the NAWAS system. In Nebraska I am only aware of 3 frequencies used:
155.745 - Sarpy County
453.650 - Lancaster County
156.000 - Hall County
If anyone knows of others please post.
Nationwide tests occur twice daily at approximately 11:00am and 9:00pm. It is interesting to hear all the states check in.