C-150 pilot reported engine failure in flight and diverted to a safe landing.

Narrative

Observed partial power loss in flight followed by repeated intermittent complete power loss and corresponding descent. [Requested priority handling with] ATC upon complete power loss and spent approximately 13 minutes in forced descent above ZZZ1 trying to regain power with different mixture settings and carb heat settings. Checked fuel valve; primer; magnetos; carb heat operation; mixture settings; oil pressure and temperature with no change in performance. Lost roughly 4000 feet of altitude in descent and was able to regain marginal climb (50-100 fpm) at reduced power with use of carb heat. Selected ZZZ as target destination for runway length and services available and available airport spacing within glide distance along route. Climbed to 10;000 feet and followed route near airports to ZZZ. Observed slightly diminished cruise performance. Landed and back taxied with no apparent issues. Had A&P mechanics inspect fuel system and called multiple A&Ps to describe issues. Performed run-up and observed normal static RPM. After viewing carb icing chart and discussing with A&P mechanics it was determined atmospheric conditions were 90-100% relative humidity and likely caused severe carb icing. Proximity to water and dam spillways may have introduced additional moisture into the air. Coupled with poor carb heat performance known on O-200 engines; carb ice likely took a long time to melt. Future operations could avoid carb ice by periodic application of carb heat when operating in conditions with high relative humidity as determined in pre-flight planning from winds and temperatures aloft.