horrible noise started today

I have a 98 dodge ram 1500 with the magnum v8. On the way out this morning it started making a horrible noise on acceleration. It was like a rough squeal. It usually squeals a little when wet or damp but not like this. The alternator gauge kept dropping down. It didn't make this noise when I stopped at a light and the gauge went back up when I turned the lights off. It only did this if the truck was moving. If I put it in park and stepped on the accelerator it didn't make this noise. It didn't act funny in any other way like it wanted to stall. It ran fine except for the problems mentioned above. Any ideas or suggestions on what the problem may be. When I say it sounded horrible it was loud and horrible. I was never so glad to stop at a light as I was this morning. (The belt doesn't feel weak either.)
THANKS!

The alternator might be seizing. It happens.

That's what I was afraid of. Nice snowy, windy weather for it too. Thanks!

When you say squeal, did it sound like the belt was slipping? Have you ever replaced the V-belt? You said that the noise quit when you turned off the lights, so that would lead me to think it's the belt. Bleed may be right also; sounds like you need to have a listen from the front of the vehicle.

It didn't sound like the belt was slipping. It almost sounded like something was grinding. The noise only stopped when the vehicle stopped, when I stopped for a light it was silent like nothing was wrong. As soon as I accelerated it immediately let loose with this noise. I did look at the belt and it felt tight when I pulled on it, for what that is worth. I didn't notice any slack in it when it was running.
When I turned off the lights the alternator gauge went back up to the middle. When the lights were on it was dropping down.
When I listen at the front of the vehicle I don't hear anything because the noise stops if the vehicle isn't moving. It is only doing it when it is in motion. I hope I'm making sense. LOL!

Maybe it's even the power steering pump that's shot? My mom's van did something similar and it ended up being that. How's your steering?

It's still just the one serpentine belt on these trucks even if they have A/C right? Or is there a separate V-belt for the A/C compressor?

Steering is fine. I have ac and all I am seeing is one belt. I drove all over yesterday and this thing ran great. I put 100 miles on it just yesterday. I get in this morning and this is what I get. It's odd.

Can't be the ps pump, if it doesn't make the noise when the engine's running and the vehicle is not moving. Has to be something in the wheels or driveline.

Why couldn't it be the pump? When the pump went on the van for whatever reason, you could be stopped and idling and there would be no sound, but as soon as you took off from a stop, the grinding would come back loud.

At this point, what I would do is take the serpentine off completely, and try and spin everything by hand. The power steering pump, A/C compressor, and alternator and see if any of them are abnormally hard to turn.

Good point, load/no load situation could make a change. Worth a listen and removing the belt, as you said.

Well, when I went out to go home it started right up and it didn't make a peep all the way home. I had someone else come and look at it and they tightened up a pulley. They said it was just a tad loose. Like it might have knocked loose from hitting a pothole hard or something.
I have had belt problems with other vehicles, my old GMC van was terrible. The belts snapped on me regularly but I have never heard a sound like this before from a belt.
Thanks for all the help. Hopefully we won't be having any more episodes for a while.