You hear them every morning, noon and night: words like isolated showers, scattered storms, widespread drizzle. These terms have been used for decades and become old hat, but they actually have very distinct meanings in meteorology.
The chance of rain includes the risk of rain never forming, the percentage that rain hits a particular town and the coverage over the region. If we think very spotty storms could form, we'll be sure to mention it, but we don't include numbers under 20 percent on the actual map. 'Isolated' is at the lower end of the range. This often means a 10-20 percent shot of rain happening.
Above this we have scattered. That typically goes up to a 50 percent chance. After that, we usually say 'rain is likely' but 'widespread' and 'expected' are also commonly used.
These terms are just used for the overall chance of rain happening in an area. They don't apply to rainfall totals, severity or how long we expect showers to last.
A slow-moving isolated storm like those near Redfield Wednesday night week can drop several inches of rain. Widespread drizzle like Sioux Falls had on Tuesday will barely register as a trace.