Thanks for clicking!

My 03 XC70CC, 211k, has beed driving very well. Today is POURING rain and very windy. I got on the freeway this morning and when I got to about 30mph, it started making a very loud whine. Like, a something really needs lube, friction whine that was constant until a stop. I couldn't really tell where it was coming from. I put it into neutral while moving to see if it would go away, it did not. I was able to accelerate through it, but it came back as soon as my speed lessened. I pulled over, parked it, and ran up the rpm's; nothing out of the ordinary. My first thought is that it has something to do with the AWD because of the amount of rain and wind. My traction was terrible, but I couldn't tell if it was just because of the water on the road or because something was malfunctioning. Is the AWD on all of the time, or does it kick on when needed? Does this sound like a common problem that coincidentally happened during very heavy rain and wind?

Forgive my lack of knowledge... I appreciate any help or guidance!