Indefinite Articles – Using ‘A’ or ‘An’ with the Word ‘Meal’

We don't use the indefinite article before plural nouns.

Yes it is justified if you're starting a story by introducing the characters and setting the scene. Here is one example of how this could go:

Diseases can spread quite suddenly and quickly. In 2015 at the New Orleans Convention Center, there were 500 people at a conference. The conference started at 8am. One of the attendees had the flu and by 3pm all the attendees were sick.

A lot of jokes start this way:

Two fishermen are drinking in a bar... A bunch of students were sitting in a classroom... Three nuns walk past a company picnic...