Re: What does an Isolated thunderstorm mean?

Leigha,

This is coming too late to help with your trip to Grand Rapids, but it may come in handy at some time in the future.

National Weather Service forecasters will forecast "isolated" thunderstorms when we are pretty certain that storms are going to form, but we only expect them to affect about 10% of the area. In other words, 90% of the area won't get wet.

Just so you know, when our forecast says...

"Widely scattered thunderstorms", it means 20% of the area will be affected.
"Scattered thunderstorms" means 30-50% of the area will be affected.
"Thunderstorms likely" means 60-70% of the area will be affected.
and if we just say "Thunderstorms", we expect that 80-100% of the area will see rain.

Problems arise, however, when that isolated thunderstorm happens to develop over the most populated city in the area. When that happens, most of the people get wet, even though only a small area received rain. So to many people, forecasters are "wrong" even when we are "right"!

Hope this helps!