Atmosphere of a Different Sort

Why is it that when the weather forecasters predict a clear and relatively warm evening, I get to ride home from work in a hailstorm?
I'd like to imagine that there was only one cloud, following me along the highway at 100 km/h spitting tiny ice pellets. Sadly, when I slowed down to 60 km/h, the hail continued. Either the cloud was bigger, in which case it was hailing on more than just me and my motorbike, or it was a very tricky cloud, not easily fooled by such schemes.