Severe thunderstorms developed over central NY during the early afternoon on the 18th, as a mesoscale convective complex moved across the area from the west.
The area was north of a weak surface warm front, with marginal instability but very strong shear.
One storm developed strong low-level rotation and produced an F0 tornado. Another storm developed a very deep, intense updraft and produced large hail. Most of the rest of the severe weather was produced by a bow echo.