B737-800
Flight Crew Air Transport Pilot (ATP)
Confusion; Distraction; Troubleshooting; Workload
Aircraft Equipment Problem Less Severe; Inflight Event / Encounter Weather / Turbulence
Flight Crew Diverted; Flight Crew Overcame Equipment Problem
Aircraft; Weather
While in a departure climb in the low flight-levels; we observed an airspeed indication disagreement and associated flags on the primary flight displays; along with an autopilot disconnect. We compared the indications among the three airspeed indicators and determined that the Captain's airspeed indication was unreliable. Since I was flying pilot and my airspeed indication matched the standby airspeed indicator; we determined that I had a reliable airspeed indication and would continue hand flying. We were in IMC and my Captain requested priority handling with ATC and requested a lower altitude. We descended until we were between layers of clouds; somewhere in the mid-teens. Once level between cloud layers the Captain ran the QRH and we formulated a plan to stay out of icing conditions and divert to a suitable airport; which was ZZZ. We changed course to head toward ZZZ and started a descent to both stay out of the clouds and set up for an arrival into the ZZZ terminal area. As we descended and flew further south; the outside air temperature warmed up and the Captain's airspeed indication started getting closer to the indications of the other two airspeed indicators until all three matched and the airspeed disagree warning flags disappeared. We still tried to avoid as many clouds as possible; but subsequent entry into clouds did not produce any more abnormalities. We landed in VMC conditions in ZZZ without incident.It appeared that the heating element(s) on the Captain's pitot tube had failed; resulting in ice accumulation and blockage of the pitot tube.
B737-800 First Officer reported an erroneous indication on the Captain's airspeed indicator; possibly due to icing conditions and a faulty pitot heat element.