PA28 pilot reports NMAC with opposite direction C172 at 1500 FT over a local reporting point. Each pilot was alerted to the others presence through CTAF; although the C172 was headed away from the airport when reporting entering on the 45.

Narrative

When I returned from my flight; traffic was using Runway 33. A lake; about 2.5 miles northwest of the airport; is a 'local reporting point' for the 45 degree entry to Runway 33. At about XA35 (local) I approached the west end of the lake from the north at 1500 FT MSL; the established pattern altitude for the runway. I had my landing light on to help the pilots see my aircraft. I was over the West end of the lake; ready to turn to the '45;' when I heard another aircraft report over the lake on a '45' (the voice was a female). I immediately keyed the mike; reported that I was also over the lake; and asked where she was I also looked to my left; over the lake; to try to see the other aircraft. When I looked back in front of me; I saw a Cessna coming at me head-on; headed more or less north-northwest away from the airport. I keyed the mike; said that I was right in front of her; and made an immediate climbing right turn to avoid a collision. I missed her by about 90-100 FT horizontally and about 10-20 FT vertically. I asked the other pilot if she saw me. She said no. I told her that I had just passed off her left and was now off to her right and behind her (she was in a right turn). I made my '45' approach. I reached downwind at about midfield. The Cessna was somewhere behind me. I was making my turn to downwind and ready to transmit my position when the Cessna reported that she was on downwind. I did not see her. My Piper has no visibility to the rear; so I asked her if she saw a Piper ahead of her. She said that she didn't know. I didn't know where she was; and she obviously didn't know where I was; but she was certainly close. So I exited the traffic pattern with a climbing right turn and subsequently re-entered the pattern and landed. I saw the aircraft parked at the edge of the apron; unsecured; unoccupied; right door open; unable to locate the pilot. I am an experienced CFI. I hoped to 'counsel' the pilot; but I couldn't find her. I attribute this incident to probably her inattention; poor orientation to the traffic pattern; and poor position reporting. My encounter with this aircraft on the '45' was a very close; dangerous near-miss. I don't know what our separation was on downwind.