I just finished the flight and safely landed at KAXQ. Forecast supposed to be broken 2500 with light snow showers and possibility of trace icing. At 8000 I was mostly above the clouds but about 60 miles out to destination I started getting into clouds. Temps were -14 d C. I kept checking wings with flash light and there was just trace amount on leading edges. All was fine until I felt change in engine noise with very slight amount of airframe vibration. Few minutes after that air speed started dropping from 140 IAS to 120 and very quickly went to 80 and then slowly went to 0. Aspen came up with 2 big X es on both screens. Pushed the throttle up and mixture advanced . Pitot heat was on since the engine start. Disconnected auto pilot and switched to alternate static source. But the changed engine noise remained ( almost felt like engine is not producing enough power ) . Also changed to alternate induction air. The airplane was flying fine with " 0 " indicated airspeed. I descended to 4 K ft and started to see ground lights and clouds cleared up After few nervous minutes airspeed became alive and Aspen came back. Rest of the flight was uneventful . Question is why pitot tube failed despite of being on all the time ( I checked it prior to departure ) And any thought about the changed in engine hum and vibration of airframe ?