Thursday will be a nice day for testing and practice sessions as a northwest flow through the midlevels of the atmosphere will keep dry air over the area. With mostly sunny skies, highs will reach the mid 80s.
A low pressure system will start to take shape over the Great Lakes on Thursday, and track southeast on Friday. As it approaches, moisture will increase as winds aloft turn to the southwest. With increasing instability as well, there will be a good chance of showers and thunderstorms. The afternoon hours will probably have the highest chance of rain, but details are still too uncertain to say for sure.
The low pressure system is expected to move slowly and linger over the region, which will keep the chance of rain continuing into Saturday. There are some model differences about how quickly the rain moves in and out, so I expect that the rain chances on Friday and Saturday will change over the next few days.