It looks like there is a screw punctured in your tire.

tsk tsk

Its your tires no doubt, those are summer tires bud, you need more individual studs to grip on the surface, think of the grooves in the tires, they act as teeth, those will stick to dry asphalt like glue, but where the surface fricition is limited by water/snow/ice you have nothing to grip.

Get some tires for snow, or at least all seasons :?

you're probably right. These tires are off of my brother'* 92 Bonneville before he sold it. We just took the tires off of that and put them on the Riviera. The tires do however say "M+*" Traction A Temperature A on them. They're Goodyear Eagles. Guess I'll be getting some new tires this weekend then.
how would these do for a snow tire?

Excellent, look at how many grooves are cut into each stud, that is what you want to see

That sucks man. At least there wasnt any damage to mechanical parts.
I once had my backend swing out, I managed to keep the car on the road. There was a pretty cool tire trail in the slush/snow though.

Yep, I remember last year hitting the breaks (it was my first year in the snow) and swerving toward a on coming bus, then back to narrowly miss the car I was breaking for then parking it right between a electic pole and a tree on the side of the road. I luckily hit nothing. I know how you feel not being any too eager to go back out on the roads.

Even a badly out of balance tire shouldn't cause a sudden loss of control.
Get your back end checked out by a pro, pronto.

And yeah, you definitely need snow tires living in That State Up North.
Here in Ohio I can get away with all-season tires and my Falkens are about the best out there, but YOU need to invest in a GOOD pair of snow tires. Also, try switching your rims out for a set of steels and hubcaps with the snow tires. 1) They don't tend to pack snow as bad as those Buick rims you have, 2) you won't have to get your tires remounted twice a year.

Hope that paint job doesn't cost too much for you. Will your insurance cover it?

Oh, yeah stay away from Goodyear snow-only tires, think Continentals, or check Consumer Reports tire comparisons.

I have an appointment Friday afternoon (12 PM) to get some Hancook snow tires installed for $480 total. Insurance would probably cover it, but when it happened it was dark out and I had gotten out of the car to check it over and I didn't see any obvious damage. (so I left.) That, and my deductable is I believe $750 anyway. (the repairs should be less than that I'd imagine.)

yup replace the tires