The weather forecasts for the Italian National Championships
here.

http://www.guarnieritrophy.it

They didn't cancel the competition on Thursday morning. The forecast for Friday
is 70% chance of thunderstorms. Yesterday the forecast for Friday was for 30%
chance of thunderstorms. When did it become the case that only a fifty percent
change of rain or thunderstorms seemed like a perfect day for flying? (Hint,
when all the others days are 70% to 90%.).