For 850-SVC70s, 1993-2000, Volvo recommends 4 (four) winter tires size 185x65x15, the same size snow tire they have recommended since the days of the 240. Tall. The usual 850-70 turbo tire is a 205x55-50x16. Relatively wide.

You might want another set of steel wheels and winter tires because:

To optimize traction in snow you want "tall and narrow". To optimize summer traction you want "low and wide".

The wheels/tires on your car are the wrong size for optimal winter traction.

You COULD use alloys, in fact the standard Volvo 850-70 15" alloy should be the right size.

But the steel wheels are cheaper.

Potholes and road hazards abound in the winter months. If you're going to bend a wheel, it's easier/simple/cheaper to deal with a bent rim if it's a $100 steel wheel rather than a $500 alloy.

The alloy wheels will corrode as has been previously stated. They ARE painted. I have not had much of th finish deteriorate on mine, though.

You'll tear those $500 alloy wheels to pieces swapping tires back and forth twice a year.

-Punxsutawney Phil

You could use the same wheel (assuming the snow tire fits). I thought
snow tires were narrower since a narrow tire "bites" through the snow
better then wide, high performance tires (so your turbo wheel is probably
not the best choice being somehat wide). (But, I don't use snow
tires where I live so I could be off base.)

Steel wheels are also cheeper which is probably why they are used.

Alloy is lighter which gives better performance (the wheels are unsprung
weight and reducing unsprung weight means the suspension components
can move and respond faster -- lighter is better, and more expensive).
In theory, an alloy wheel gives a better ride since the tire/wheel
can follow the pavement variations easier (beacuse there is less weight
moving and less inertia). They should also give better traction and
allow the suspension to work better. But in snow, who cares, so use a
cheaper, steel wheel.