You might want to check your water pump bearing, I had a squeal sound that was low pitched and sounded like it was coming from the alternator, after putting a long handled screw driver on the alternator and placing my ear on the end to the screw driver, I was able to pin point the sound and it was coming from the water pump...you might want to check it out before pulling the alternator again...usually that front bearing doesn't go out...good luck..

Thanks highbinder. I will give that a check before I pull it out again. It is more of a high pitch squeal and since I removed and replaced the rear bearing the sound changed just a little. I was thinking I had maybe disturbed it a little when cleaning. When I inspected the rear bearing I thought for sure that would have been it but it wasn't. It really is pronounced when it gets below about 40 degrees and it hasn't been quite that cold yet. I will break out the stethoscope and keep it handy for the next time it happens.