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NWS Jacksonville Home
» Definitions
Dense Fog/Smoke Advisory - Issued when the visibility decreases to
1/4 mile or less in dense fog or smoke.
Dust Storm Warning - Issued when the visibility decreases to 1/4
mile or less
and wind speeds of 25 mph or higher are occurring. In such an episode, if the
winds reach 40 mph or gust to 58
mph, then a Dust Storm and High Wind Warning will be
issued.
Excessive Heat Warning - Issued when daytime high temperatures
reach
105 degrees or higher with nighttime lows at or above 80 degrees for two
consecutive days.
Freeze (Warning)-Issued when the air temperature is expected to be
32 degrees or below for 2 or more hours. Issued as NPW and headlined in
zones.
Frost - The formation of ice crystals on the ground or other
surfaces whose temperature has fallen below 32 degrees. A statement on its
occurrence should be included in the body of the forecast. Examples: PATCHY
FROST or SCATTERED FROST POSSIBLE. Frost can occur when the air temperatures
is in the middle or upper 30s.
Hard Freeze -Temps 27 or less for 2 or more hours.
Heat Advisory - Issued heat if the heat index is expected to be 110
degrees or higher. Outside of advisory criteria, heat indices of greater than
100 degrees will be put in the Zone Forecasts.
High Wind Warning - Issed when non-thunderstorm winds with
sustained
speeds of 40 mph or greater or gusts to 58 mph or greater are expected for one
hour or longer.
Inland High Wind Warning for Hurricane Force Winds - High winds can
occur a few hundred miles or so inland from the coast of a landfalling
tropical cyclone. Areas near the coast are covered with hurricane or tropical
storm warnings. However, hurricane and tropical storm warnings are not
appropriate for inland areas since they are perceived to be associated with a
marine environment and include storm surge dangers. Therefore, tropical
cyclone produced winds over inland areas are covered by an Inland High Wind
Warning for Hurricane Force Winds.
Lake Wind Advisory - posted when a wind speed is expected to be
sustained 20 to 25 mph.
Wind Advisory - posted when a wind speed is expected in the 25 to
39 mph range.
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