Pilot reported an airspeed critical malfunction during cruise and diverted to a suitable airport where a safe landing was executed.

Narrative

Flying return legs with family from vacationing. During 45 minutes or so into cruise flight with autopilot engaged at 26;000 ft.; I noticed an Indicated Airspeed Annunciation on both Primary Flight Displays. The airspeed was showing about 9 knots higher on right side PFD (Primary Flight Display). The indicated airspeed would slowly vary from 7 knots to 9 knots higher on right side PFD; which was on ADC #2. I referenced a checklist covering avionics which stated to use alternate static selector if symptoms persist; but decided not to activate as I had two independent sources for airspeed. In this particular aircraft; the backup electronic Airspeed Indicator (ASI) utilizes the #1 pitot static system. On descent with autopilot engaged to my usual fuel stop; I noticed the airspeeds on the Left side ASI and the standby ASI decreasing abnormally while the Right side ASI was increasing as normal as I hadn't reduced any power at this point. While mindful of the decreasing airspeed indications on the left side instruments; a couple minutes after descending a few thousand feet the autopilot now started uncommanded occilations to the left and right and I also sensed a yaw movement at the same time so I disconnected the autopilot and hand flew the plane while descending to 22;000'. I advised ATC of my situation and asked for a change in destination to a maintenance facility that was a few miles further than a major airport that was closer. ATC was very helpful and did try to help troubleshoot my issues by asking pertinent questions regarding any icing and if my pitot heats were working. I hadn't flown through any icing and both pitot and stall heat was working normally. Within a couple minutes both left side airspeed indicators went to zero; and the standby ASI display red flagged. I updated ATC on my instruments status. Sometime around this point ATC asked me if I was requesting priority handling; and I said yes I was; and would be landing at the nearby major airport that would have a fleet of vehicles waiting for my arrival and assisting if needed to; that was now about 15 minutes away.. As I was descending to a lower altitude and getting into warmer temperatures; my OAT indicating -13C; both the left airspeed and standby airspeed indicators came back to life and appeared to match the right side airspeed indicator now. I again updated ATC on my flight status; and advised I would still be landing at the major airport. ATC advised they would keep the vehicles in position while I landed as a precaution; which I appreciated. After an uneventful landing; I taxied off the main runway and waited on the taxiway while I debriefed with the crew representative over ground control frequency. The vehicles then followed my to my parking spot at the FBO; which was uneventful. All ATC personnel that I had communications with were all very polite; helpful and professional. What I believe may have played a part in this scenario was on a previous trip the plane was parked outside; had some weather while the plane was there. It was windy; rained; and one of the static covers had likely blown off in the wind and was unrecovered. While taxiing out for return flight there was an airspeed indication on Right airspeed indicator only; but only then when taxiing from parking spot in a crossing tailwind. Lineup and takeoff all systems normal and continued normally. The plane flew multiple legs in about 8 hours flying time after that in freezing temperatures without any abnormalities. I did use new replacement static plug covers prior to the flights on vacation. Water in the static system likely contributed to this event. It would have been prudent for me to further investigate any chance of moisture being ingested into static vent systems.