I live 50 miles north of NYC and I've been complaining for decades. I created this screename in the late 90's on the old Bill Evans AccuWeather weather forum and there was good reason I chose it. I had several discussions with Bill back in that time period and he said he thought the yearly average in CP was probably 4-5 inches higher than what was actually recorded.
Years later 2011-2014, I discussed the problem with the NWS many times leading to the change to the conservancy taking the measurements in 2015. They always acknowledged the problem but always stated how difficult it is to get a reliable person to the park to measure. They even asked at one point if I wanted to do it, considering the distance I politely declined.
Like I said earlier they then took the measurements from the Central Park zookeeper in late 2014 and started with the Conservancy taking the measurements. To repeat myself it did improve significantly from 2015-2019 but has been pretty much a shit show again since 2020.
There are most likely several reasons for their constant under measurements. Where they measure, when they measure, not measuring immediately after events end so there is time for compression, settling or melting and having an organization measuring that doesn't seem to care about accuracy and timeliness.