Overcast

Definition

Overcast, written as "OVC" in the METAR observation, is reported when the cloud cover is observed to equal eight oktas (eighths). An overcast sky may be explicitly identified as thin (mostly transparent), but otherwise considered opaque—which always constitutes a ceiling in aviation meteorology.

Appearance

Sometimes clouds can be of different colors such as black or white, but overcast usually refers to darker skies. In some cases, it can be characterized by almost zero distinction of borders of clouds. Or the sky may be covered by a single type of cloud, such as stratus, turning the whole sky into a dull white color.

Length

Periods of overcast weather can range from a few hours to several days. Overcast weather can also affect people suffering from seasonal affective disorder.

The same weather when observed from above may be referred to as undercast, generally by pilots reporting in-flight weather conditions.

References

fr:État du ciel

References

1. "Aerodrome Weather Report". [[World Meteorological Organization]].
2. "Overcast". [[American Meteorological Society]].
3. World Meteorological Organization. "Overcast". Eumetcal.
4. ''Oxford English Dictionary'', 3rd ed. (website), s.v. “overcast," 2a and 2b. http://www.oed.com/view/Entry/134377#eid32922408 (Accessed September 7, 2016).
5. "Undercast". [[American Meteorological Society]].