Topic: Forecasting Icon Behavior

[SteveM]

Any Acurite'ers out there have an idea on how to interpret this? I read it as if the temp is this to this and the chance of precipitation is p% and cloud cover is cc%, then the icon displayed will be as per below. Assuming that interpretation is correct, why are some clouds underlined with dark high lights?

http://www.acurite.com/images/Forecasting-C.jpg

Thanks
Steve