First, thanks for great weather coverage on WRAL. My question: What is the difference between partly sunny/mostly cloudy or partly cloudy/mostly sunny. It seems to me that the pairs are the same thing. Is there a reason to use one rather than the other? A minor point, but something I've always been curious about... Susan B

MIKE MOSS SAYS:     Susan,   Both of those terms represent a mix of clouds and open sky, ranging from about three to five eighths (or "oktas") of the sky covered by opaque clouds, and the National Weather Service officially defines the terms interchangeably. However, some forecasters lean toward using "partly sunny" when a bit more cloud cover than open sky is expected, and vice versa for "partly cloudy."

In addition, one would use partly cloudy rather than partly sunny for nighttime skies that fall within that range of cloudiness. Likewise with "mostly clear" versus "mostly sunny," both of which refer to around 1-2 oktas of cloud cover.