No, it's not that exciting; it's a combo warning for the inclement weather and the motorcade on 15th Street:
Everyone, just coming back from the post office you might want to avoid 15th and L Streets for the President's Motorcade is about to be set up for his... . So the police department, etc will be cutting of streets. Where they are going who knows but a good guess would be back up 15th towards the White House. So plan accordingly to avoid a already traffic congestion and who knows when they will clear the motorcade setup.
No, I didn't add the ellipsis, nor do I know what it's there for.
Seconds after I finish reading it, I overhear someone ask aloud, "what's a motorcade?"