Djohn

Apologies if this is in the wrong thread (it's a while since I've been on) I have an STI forester which developed a problem yesterday. The steering wheel wobbles from side to side and if I get up to 50mph the car feels like its driving over a ploughed field. Its not a tyre problem, tyres are Bridgestone potenzas and have been on for over a year and I checked the pressures this morning. My local garage can't fit me in until Friday so just as a heads up, any ideas how bad this could be?