Narrative:

About an hour before take-off; I called the AWOS at my destination airport; which is also my home base. It reported a 5;000 foot ceiling and light northwest wind. Because there is some concern with the reliability of the AWOS; I generally also call the airport and did so on this occasion. I spoke to the airport manager; who confirmed that there was a very high overcast ceiling and that you could see the tops of all the mountains in the area. He also said that he could see brighter sky and maybe even some clearing to the west. I also checked the current ATIS/AWOS reports for several nearby airports and they all showed ceilings between 1;000 and 5;000 ft. I filed an IFR flight plan to ZZZ which is about halfway between my departure airport and my final destination; planning thereafter to fly under the ceiling because my home airport does not have an instrument approach. I took off later; executed the GPS approach into ZZZ. I broke out of the clouds at around 1;000 AGL and canceled my IFR flight plan. I then followed a highway just east of the airport and was easily able to remain 500 ft below the clouds. Later; however; the cloud layer gradually became lower and I started monitoring the terrain feature of my garmin 530 more closely. Somewhat later I had to descend to around 500 ft AGL to stay below the cloud cover. I was able to continuously see and follow the highway and never flew into clouds; though I am certain that I was only just under the cloud cover and did not have a 500 foot clearance between them and the airplane. At this point; I seriously considered turning around and going back to ZZZ. I also considered flying straight ahead and climbing into IMC and requesting an emergency IFR clearance. The idea of turning around was the more attractive of those two options; but given the somewhat narrow corridor and the conditions in which I was flying; it was not what I decided to do. Instead; I decided to continue because I could see the highway well into the distance and the conditions did not look like they were getting any worse. With the report I had received about conditions at my destination that idea seemed to be the most reasonable. On the east side of the ridge; the conditions did improve and I was once again able to stay at least 800 to 1000 ft off the ground and 500 ft under the clouds. As I got closer the conditions improved even more; but they never did get to what I had expected them to be. I landed safely at my home base; where the ceiling was approximately 3500 ft AGL. In retrospect; as I could see that the conditions were getting worse and not better as I had expected; I should have simply turned around and gone back to ZZZ. That course of conduct would have precluded flying under less than required separation from clouds and maybe even terrain.

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Original NASA ASRS Text

Title: An M20 pilot pressed on VFR despite lowering ceilings which necessitated less than regulatory separation from clouds enroute to his home airport.

Narrative: About an hour before take-off; I called the AWOS at my destination airport; which is also my home base. It reported a 5;000 foot ceiling and light northwest wind. Because there is some concern with the reliability of the AWOS; I generally also call the airport and did so on this occasion. I spoke to the airport manager; who confirmed that there was a very high overcast ceiling and that you could see the tops of all the mountains in the area. He also said that he could see brighter sky and maybe even some clearing to the west. I also checked the current ATIS/AWOS reports for several nearby airports and they all showed ceilings between 1;000 and 5;000 FT. I filed an IFR flight plan to ZZZ which is about halfway between my departure airport and my final destination; planning thereafter to fly under the ceiling because my home airport does not have an instrument approach. I took off later; executed the GPS approach into ZZZ. I broke out of the clouds at around 1;000 AGL and canceled my IFR flight plan. I then followed a highway just east of the airport and was easily able to remain 500 FT below the clouds. Later; however; the cloud layer gradually became lower and I started monitoring the terrain feature of my Garmin 530 more closely. Somewhat later I had to descend to around 500 FT AGL to stay below the cloud cover. I was able to continuously see and follow the highway and never flew into clouds; though I am certain that I was only just under the cloud cover and did not have a 500 foot clearance between them and the airplane. At this point; I seriously considered turning around and going back to ZZZ. I also considered flying straight ahead and climbing into IMC and requesting an emergency IFR clearance. The idea of turning around was the more attractive of those two options; but given the somewhat narrow corridor and the conditions in which I was flying; it was not what I decided to do. Instead; I decided to continue because I could see the highway well into the distance and the conditions did not look like they were getting any worse. With the report I had received about conditions at my destination that idea seemed to be the most reasonable. On the east side of the ridge; the conditions did improve and I was once again able to stay at least 800 to 1000 FT off the ground and 500 FT under the clouds. As I got closer the conditions improved even more; but they never did get to what I had expected them to be. I landed safely at my home base; where the ceiling was approximately 3500 FT AGL. In retrospect; as I could see that the conditions were getting worse and not better as I had expected; I should have simply turned around and gone back to ZZZ. That course of conduct would have precluded flying under less than required separation from clouds and maybe even terrain.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.