Anyone Ever Have a Whistle From the Rear Slider That's Blower Related?

For the longest time I thought I had a wind noise whistle because it sounded like it came from the back section of the roof. It wasn't always there so it was hard to diagnose. One day it was there and I paid attention and as I slowed to a stop I realized it was still there. Then, a few days later I discovered that it was related to the blower setting on the HVAC control. The higher the setting the louder the whistle. Today I got it to do it again and began investigating since I was at a stop. After a few seconds I pushed the slider outwards (towards the tailgate) and as it got closer to the passenger section of glass the noise got quieter and went away. So, my whistle appears to be from the glass not sealing itself.

Thoughts?

I'm still under warranty (35k miles) so I would guess that my best bet is to schedule to have it fixed under warranty but this is a PITA and I wanted to make sure that there wasn't something simple I could do to fix it or if anyone else had had this happen.