Yep, definitely diversions starting for the next line of storms.
2186 ATL-LGA definitely headed back to LGA now
1822 DTW-LGA headed back to DTW
2820 MIA-LGA diverting to ATL
4252 MCI-LGA is diverting to JFK which seems odd since the storms would likely impact JFK too.
And UA3800 CLE-EWR is headed to BDL.
I'm sure there are more.
ETA: 1822 and 2186 now delayed until the morning. Continuation of 2820 onward from ATL scheduled for 7:00am.