This is a question that has perplexed the general public for many years. So, HOW THE WEATHERWORKS went to Jannie Gibson of NOAA's National Weather Service (NWS). She provided these proposed definitions of terms to be used by the NWS in describing the state of the sky. They are from The NWS Operations Manual, Chapter C-11 (Zone Forecast Guidelines and Procedures).
"The following basic terms should be used to describe the predominant sky condition in each forecast period, except when it can be easily inferred from a precipitation forecast. Other terms may be used if they are well understood by people in an area and better describe expected conditions. Note that the term "FAIR" shall not be used to forecast sky condition."
|
DAY |
NIGHT OR DAY |
PREDOMINANT SKY CONDITION |
||
| Cloudy | Cloudy | 8/8 opaque* clouds | ||
| Mostly Cloudy or Considerable Cloudiness |
Mostly Cloudy or Considerable Cloudiness |
6/8 - 7/8 opaque* clouds | ||
| Partly Sunny | Partly Cloudy | 3/8 - 5/8 opaque* clouds | ||
| Mostly Sunny | Mostly Clear | 1/8 - 2/8 opaque* clouds | ||
| Sunny | Clear | 0/8 opaque* clouds |
* opaque means that an observer can not see through the clouds; the sun, moon , stars, and blue sky are hidden.
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This page was last updated on February 14, 2006.