Yes those alerts are typically screaming loud and on blue screens on the TV.
https://en.wikipedia.org/wiki/Emergency_Alert_System#System_tests
https://www.google.com/search?q=emergency+broadcast+alert&source=lnms&tbm=isch&sa=X&ved=2ahUKEwi2jbH37oruAhWF1FkKHalLAdAQ_AUoA3oECBEQBQ&biw=1536&bih=774
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