Almost lost control and hit a guard-rail 30min ago.
I was going down hill at about 50-55mph. There appeared to be groves worn in the snow down to bare pavement, but there were light flurries (the snow had stopped 5hrs ago and just started to spit again). I had to turn left at almost the bottom of the hill (I'm guessing 2-4% grade). I took my foot off the gas and let the truck start to slow itself down. I began to brake lightly around 45mph. I think I shifted into 4th. All of a sudden I realized I wasn't going where I wanted to go and all I could see in front of me was a guard rail. All I thought was "don't hit the guard-rail!!!". I stopped braking and steered left since the back end was fish-tailing to my left. Then it fish-tailed to the right so I counter steered. Then I realized I should push in the clutch so I did. The truck then fish-tailed to the left again. And finally some very sudden and minor fish-tailing right, then left, then it straightened out. By this time I was down to maybe 30-35mph and had missed the turn, which I didn't care that I missed. I proceeded, with my heart about to jump out of my chest, another 2mi down the road to a place where I felt safe to turn, stop, and turn around. While I was stopped, I got out, looked over the tires, and pissed (I'm so glad I didn't piss my pants!) because I needed too just before this happened. I then headed back to the turn that I missed. This time I was going up-hill and felt much better approaching it.
I have no idea what actually caused this to happen. I didn't feel like I was braking very hard at all. All I can figure is there was just enough snow on the pavement to make that magical, and a pain-in-the-ass, glaze on the pavement. I couldn't just let the truck spin because of 1) I would have hit the guard-rail and 2) I might have swung into on-coming traffic which luckily at the time there was none. Also, there wasn't a car behind me for at least a 1/2 a mile. If there would have been someone behind me, they probably would have slammed on the brakes and either hit me or lost control themselves...or a combination of the two.
Prior to this I had driven home, someone's house, home, to my great-uncle's for Christmas Eve dinner, home, and then this happened on my way back out the that someone's house. So I put a few miles on today; maybe 100.