An unusually warm and muggy airmass provided plenty of moisture and energy for some strong thunderstorms that left parts of Portland, Maine under water.
The day started with temperatures and dew points around 70 degrees. The boundary layer was very moist and outside of an inversion or 'cap' aloft, every indication was that this day would bring weather of interest. A sea breeze did develop in the afternoon, but it never got very far inland. Temperatures in Cape Elizabeth were about eight degrees (F) lower than here in South Portland, with South Portland reaching the 83°F mark. There appeared to be a large amount of 'training' going on again in New Hampshire, where storms the day prior left almost 5 inches of rain in some places like Canaan. The 'cap' kept a lid on most of the convection in Portland, but the mountains provided the necessary break to allow for air to rise and form thunderstorms.
In downtown Portland heavy rain caused water to back-up onto and flood Commercial street. Several parts of high street were washed out, closing it to traffic.
Commercial Street in Portland, Maine
Close-up of Commercial Street flooding
Water flowing out of manholes on the Eastern Promenade
Lightning near Bug Light in South Portland
