Eric Fischer maps the patterns of social media use. A National Alert system could take clues from the spread of social media. (Eric Fischer)

It will be the first time the Federal Emergency Management Agency has attempted to alert the entire nation at once with its Emergency Alert System. While the program hopes to reach as many people as possible as quickly as possible, two means of communication are still missing from the system: the Internet and mobile phones.

The purpose of the test, of course, is to see how prepared the United States is in the event of a natural disaster, national emergency or terrorist attack. A 30-second warning video will air and cable companies will report how many estimated viewers saw the alert. Television viewers and radio listeners are expected to simply bear with the warning — no ducking under desks required.

For everyone else, though, no ducking or watching will be required. If you’re not in front of the televsion, you may miss the message. FEMA still does not have a fully rolled out plan to reach people via text messages or Internet updates.

FEMA launched a national alert system for phones in May, called PLAN, that reaches some smartphones on some national providers. The program sends out free text messages about emergency situations. However, only about 50 percent of Americans own smartphones and the program has not fully been adopted across the country.

As for Internet alerts, they work mainly on an opt-in basis. FEMA has an iPad and Android app and Twitter and Facebook accounts. However, this system of requiring Americans to actively seek out FEMA differs dramatically from the PLAN system or the Emergency Alert System. The alert system pushes messages out to Americans whether they want them or not. FEMA works with cable providers to get the word out.

It would be interesting to see the agency undertaking something similar in partnerships with major Internet companies. Could it be possible for the Google logo to turn into an alert message? Or for Twitter’s promoted ads — which appear in user timelines — to be a message from FEMA?

It may not be that long in the future for a truly integrated nationwide alert system. FEMA is working on an Integrated Public Alert and Warning System (IPAWS) that will employ all communication devices. Until then, though, if you want to be warned, tune into the television at 2 p.m.

To learn out more, watch The Post’s Ed O’Keefe give you the rundown on what you need to know about the alert: