I have never heard of PNW and I live in the US. Also, this person is from Croatia.
Edit: I guess that doesn't disqualify this person from picking up US lingo, but thinking about it further, someone who didn't grow up in the US might be more likely to use regional abbreviations in general contexts.
Edit: I guess that doesn't disqualify this person from picking up US lingo, but thinking about it further, someone who didn't grow up in the US might be more likely to use regional abbreviations in general contexts.