I had the situation you describe when the pointy end of a maple-tree 'propeller' seed fit perfectly into the front driver-side sunroof drain, clogging it completely.
I discovered the clog while driving during an intense inches-per-hour deluge when water started dripping down the A-pillar.
Drove into a self-service carwash bay to get out of the rain, so I could open the sunroof and diagnose the problem.
Quickly fixed the leak by pulling the seed out of the front drain, removing the clog.
As I recall, the front drains for the sunroof are down inside the front of the sunroof opening, near the corners where the sunroof glass would be when closed, but accessible when the sunroof glass is fully opened. (I don't own the car anymore, so I can't take photos.)
There are also rear sunroof drains with clear blue plastic tubes that end up down behind the rear wheel wells, but your leak sounds like a clogged front drain.
My 2003 Vibe Base Auto 2-tone Salsa "SalsaWagon" was built in May 2002. I acquired it in Feb 2004/Traded it in on a 2016 Honda HR-V in Feb 2018
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