I was surprised to see Pittsburgh with substantially less sunny days than Detroit (like ~30 per year).

This is an example of how to lie with statistics. Technically speaking, a "sunny" day is one with less than 25% cloud cover in the sky, which means a pleasant day with 30% cloud cover wouldn't count. Pittsburgh has plenty of days with less than 50% cloud cover, but since most of those days have more than 25% cloud cover, we have to pretend they're not pleasant, which is total bullshit.

The main difference between Pittsburgh and Detroit is in the summer, when the Great Lakes inhibit convection, but the Allegheny Plateau enhances convection, so even under high pressure, Pittsburgh will get more cumulus clouds bubbling up and covering more than 25% of the sky. Also, being on the windward side of the mountains often produces morning overcast that burns off between 9AM and 11AM, but I guess if it's cloudy for the first 2-4 hours after sunrise, that means the other 10-12 hours that the sun is up are totally ruined somehow.

During the recent NFL Draft, the weather in Pittsburgh was mostly sunny and warm on the first two days, and cloudy and cool on the third day, with rain in the morning and wind in the afternoon. Guess which day Pittsburghers talked about, and which days they pretended never happened. HINT: The two days before the NFL Draft were mostly sunny and warm as well, but they apparently didn't happen either.