Narrative:

Flight departed at approximately XA15L after receiving a weather briefing for the route of flight and weather was VFR and predicted to remain VFR for the flight. Prior to reaching ZZZ VOR; a shelf of clouds started to develop about 1;000 ft below the aircraft and ceilings above about 2;500 ft above the aircraft. In between the shelf and base; I could make out ZZZ1 in the distance; so I requested VFR on top clearance to ZZZ. I received the clearance via radar vectors and flew the vector. The temperature was at 32 degrees F and I requested vectors that would not make me penetrate visible moisture. At this point the shelf merged with the bases and prior to continuing I looked behind the aircraft and saw a cloud rolling in behind the aircraft; almost as a curtain drawing making it impossible to divert. I followed the vectors to the best of my ability but was distracted making it difficult. After penetrating a cloud; I noticed approximately 1/8 inch of ice on the leading edge. At this point; I announced my icing condition to ATC and they gave me priority handling. Shortly after I declared an emergency and ATC gave me vectors for the ILS runway xxl. I tuned and identified the ILS and tried to track it; but I was unable to receive the glideslope. I then received vectors for the airport and descended to 400 ft AGL. At this point I had closer to 1/4 - 1/2 inch of mixed ice on the wings. I saw visual of the airport abeam runway yyr and circled to land runway xxl using no flaps and had a smooth; safe landing. After landing; I proceeded to the FBO with airport rescue fire fighting following me in. After examining the aircraft; the propeller was clear and the wings had about 1/3 inch of ice proceeding about 6 inches aft of the leading edge.

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Original NASA ASRS Text

Title: C172 pilot plans VFR flight and receives weather brief for VMC along the route of flight. Low ceilings and icing conditions are encountered causing the declaration of emergency and vectors to the nearest airport by ATC.

Narrative: Flight departed at approximately XA15L after receiving a weather briefing for the route of flight and weather was VFR and predicted to remain VFR for the flight. Prior to reaching ZZZ VOR; a shelf of clouds started to develop about 1;000 FT below the aircraft and ceilings above about 2;500 FT above the aircraft. In between the shelf and base; I could make out ZZZ1 in the distance; so I requested VFR on top clearance to ZZZ. I received the clearance via radar vectors and flew the vector. The temperature was at 32 degrees F and I requested vectors that would not make me penetrate visible moisture. At this point the shelf merged with the bases and prior to continuing I looked behind the aircraft and saw a cloud rolling in behind the aircraft; almost as a curtain drawing making it impossible to divert. I followed the vectors to the best of my ability but was distracted making it difficult. After penetrating a cloud; I noticed approximately 1/8 inch of ice on the leading edge. At this point; I announced my icing condition to ATC and they gave me priority handling. Shortly after I declared an emergency and ATC gave me vectors for the ILS Runway XXL. I tuned and identified the ILS and tried to track it; but I was unable to receive the glideslope. I then received vectors for the airport and descended to 400 FT AGL. At this point I had closer to 1/4 - 1/2 inch of mixed ice on the wings. I saw visual of the airport abeam Runway YYR and circled to land Runway XXL using no flaps and had a smooth; safe landing. After landing; I proceeded to the FBO with Airport Rescue Fire Fighting following me in. After examining the aircraft; the propeller was clear and the wings had about 1/3 inch of ice proceeding about 6 inches aft of the leading edge.

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.