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Calculate Cloud Base Above Ground

 Tempature �F
 Duepoint �F
 Cloud base in feet AGL =

National Weather Service Graphical Forecasts - Portland, OR

During part of the year in the Northwest we often have cloud bases that are 1,000 feet or less AGL. This can make it hard to plan a flight that is five or so days out. Terminal Area Forecasts provide forecasted cloud bases but they don't extend past one day. It is possible to estimate the base of clouds by subtracting the temperature from the dewpoint, dividing the result by 4.4, and multiplying that by 1,000. Therefore, using forecast temperatures and dewpoints, it is possible to estimate cloud bases.

The above web page can be used in conjunction with this page to forecast cloud bases for a period up to one week out. Remember, there is probably a reason the weather service does not provide this information.

Last modified 09/19/07