A PA28 pilot on a long cross country but without a flight plan lost flight following contact with ATC over the mountains. Lack of communication triggered preparation for a search.

Narrative

I was flying from ZZZ1 to ZZZ2 and was in radio/radar contact with Center. My radio started to have a squeal in it; the tops of the clouds kept rising as I was trying to stay above them and go around the higher tops. Center turned me over to another Center and I tried to contact them but couldn't. At this time there was a higher wall of clouds in front of me and I was trying to decide which way to go; either northwest or northeast. I went to the northeast as it was closer and as I came around the wall of clouds; I could see that I was not going to remain VFR at 17;500 FT. I made a 180 degree turn and started to look for an area to descend. I found a large area in which to descend from 17;500 FT to 6;500 FT VFR. I found that I was southwest of ZZZ3 Airport and from there I proceeded to ZZZ4 where I landed; refueled; and assessed the weather toward ZZZ2. Weather looked favorable to ZZZ5 so I proceeded there. It was late when I arrived at ZZZ5 and the weather did not look VFR to ZZZ2. So I spent the night at ZZZ5. I had my cell phone on after I landed but I could not get service. The next morning; I flew to ZZZ2 where; upon contact with the Tower; I was told that I had been reported as missing. ATC had lost radar contact with the aircraft southwest of ZZZ3. Ground parties had assembled with 5 aircraft ready to start searching as soon as weather permitted. I was contacted by the FAA on my way home from the ZZZ2 Airport and I explained what had happened. I made several phone calls to various agencies who had left phone messages at my home. I have reviewed this flight with the aide of my handheld GPS and notes from my flight log. 1) Pilot workload was high due to weather. 2) Radios were not working properly. 3) In retrospect; I probably should have called ATC by phone when I landed at ZZZ5.