Will cloud cover affect tomorrow's temperature at 12Z?

At night, clouds tend to slow down the rate at which the earth's surface cools off, so nighttime temperatures tend to be warmer on cloudy nights than on clear nights, all else being equal. In the forecasting assignment, clouds are deemed to affect tomorrow's 12Z temperature significantly if at least 3/4 of the sky is covered by clouds for at least three of the six hours leading up to and including 12Z tomorrow (that is, from 7Z through 12Z).

One tactic for dealing with this item is to consult the National Weather Service point forecast, which provides relatively vague (but still useful) cloudiness forecasts for 12-hour periods from 6 am to 6 pm and from 6 pm to 6 am for the next several days. From the class iLearn and backup Web sites, under Forecasting Assignment, go to Maps/Images > Surface Analyses; then look under "Forecasts, Climate Data, etc." and select the link to "Forecast for Oakland International Airport" or whichever location for which you're currently forecasting.

  • wunderWiki Web site's attempt to decipher the wording of the NWS's cloudiness forecasts (http://wiki.wunderground.com/index.php/Educational_-_Partly_cloudy)