Do you know what the gauges read? I just had my compressor diagnosed as bad. Did find a neat article online that had a diagnosis chart. There were links to several more articles at the bottom that were helpful too. http://www.aa1car.com/library/ac98.htm
I had similar symptoms. Started blowing warm air. Definitely humid. (but I'm in Florida) My low pressure side gauge read 70 and my high pressure gauge was 200. Added some freon just in case - still no dice. Took it by an AC shop who evacuated the whole system and then refilled it to factory spec. They said that would help pull out moisture if that was the problem - as well as any additional freon if we'd overcharged it. They also checked to be sure my fan wasn't clogged or blocked - but it was blowing fine.
While putting the freon back in the system - the pressure was instantly too high. I'm told the low pressure side should read somewhere around 35. (25 and 45 are the cut off ranges) So 70 being so high - the compressor is having a hard time doing its job. Or shall we say NOT doing its job.
Diagnosis - compressor is waving goodbye.
I did read that if you want to look for an ice blockage somewhere along the lines that you can use a laser/infrared thermometer to trace down the lines and look for an extreme temp change. (aka: blockage of ice) I got a great deal on one today - -4F to +968F range for only $26.00. Shoot me a note if you want to know where I got it.