That happened to a smaller extent in my 97 SW. Check for leaks in your seals/roof/windows. I did this at night with a Mag light. If you can see light then you can see water. I found a couple of leaks in my Door seals and on the roof.
I am going to wait until the winter is over and remove my entire head liner and take a look at it from the inside. I think it will solve any leaks I have as well as keeping the exterior looking good. I made some temp. sealing with a silicone marine sealer on the outside, but it took some time to do a clean job, which prompted me to think about doing from the inside.