What was found
RIGHT SIDE PITOT LINE BECAME BLOCKED INFLIGHT AFTER EXTENDED OPERATION IN AN AREA OF VISIBLE MOISTURE AT BELOW-FREEZING TEMPERATURE. ALL PROBE HEATS WERE ON AND FUNCTIONAL AT THE TIME AND FOR THE ENTIRE DURATION OF FLIGHT PRIOR TO THE LINE BLOCKAGE. AIRSPEED ON THE RIGHT-SIDE PFD AND STANDBY INSTRUMENT SLOWLY DECREASED, WHICH CAUSED AN IAS MISCOMPARE ANNUNCIATOR. I STARTED A DESCENT FOR WEATHER AND THE AIRSPEED ON THE RIGHT-SIDE PITOT LINE (RIGHT PFD AND STANDBY) RAPIDLY DECREASED TO ZERO BEFORE AN IAS RED ANNUNCIATOR APPEARED. PRIOR TO THIS, I SWITCHED THE RIGHT-SIDE PFD TO ADAHRS 1, WHICH KEPT THE AUTOPILOT RUNNING FOR A WHILE UNTIL THE MISCOMPARE BECAME TOO GREAT AND THE AUTOPILOT DISCONNECTED. AUTOPILOT WOULDN'T REENGAGE UNTIL I PULLED THE ADAHARS CH 2 CIRCUIT BREAKER. AFTER DESCENDING OUT OF VISIBLE MOISTURE, THE RIGHT-SIDE AIRSPEED RAPIDLY RETURNED, AS SEEN ON THE STANDBY INSTRUMENT, AND WHEN THE ADAHRS 2 BREAKER WAS RESET, ALL SYSTEMS ON INDEPENDENT ADAHRS UNITS RETURNED TO NORMAL WITH NO FURTHER ISSUES.