The National Weather Service
issues forecasts for sky condition, temperature, wind, and precipitation
probability on a routine basis. Because the weather is always changing, the
terminology used in these forecasts is also quite variable. Listed below are
descriptions of regularly used weather terms that should give you a better
understanding of each forecast.
The sky condition describes the predominant/average sky condition based
on eighths of the sky covered by opaque (not transparent) clouds. If a high
probability of precipitation (60% or greater) is expected, then the sky condition
may be omitted since it is inferred from the precipitation forecast.
The temperature in a forecast is used to describe the forecast maximum and minimum temperature,
or in some cases, the temperature expected at a specific time.
The wind describes the prevailing direction
from which the wind is blowing, with speeds in miles per hour. Wind velocity
is normally included in the first five periods of a zone forecast, although
descriptive terms may be used in all periods.
The Probability of Precipitation (POP)
is defined as the likelihood of occurrence (expressed
as a percent) of a measurable amount of liquid precipitation (or the
water equivalent of frozen precipitation) during a specified period of time
at any given point in the forecast area. Measurable precipitation
is equal to or greater than 0.01”. Unless specified otherwise, the time
period is normally 12 hours. The forecast area, or zone, is generally considered
to be a county. NWS forecasters use such categorical terms as occasional,
intermittent, or periods of to describe a precipitation event
that has a high probability of occurrence (80% +) but is expected to be of an
“on and off” nature.
Website Owner: National Weather Service
Juneau Forecast Office
8500 Mendenhall Loop Road
Juneau, AK 99801
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Page last modified: 10-Nov-2011
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