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AIRMETs
An AIRMET (AIRman's METeorological Information) advises of weather
that may be hazardous, other than convective activity, to single engine,
other light aircraft, and Visual Flight Rule (VFR) pilots. However, operators
of large aircraft may also be concerned with these phenomena. Since the
majority of training missions at NASP are VFR, AIRMETs are extremely important.
AIRMETs are issued by the National Weather Service's Aviation Weather
Center (for the lower 48 states and adjacent coastal waters) for the following
weather-impacted reasons:
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Instrument Flight Rules (IFR) or Mountain Obscuration -
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Ceilings less than 1000 feet and/or visibility less than 3 miles affecting
over 50% of the area at one time.
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Extensive mountain obscuration
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Turbulence
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Moderate Turbulence
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Sustained surface winds of 30 knots or more at the surface
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Icing
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Moderate icing
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Freezing levels
These AIRMET items are considered to be widespread because they must be
affecting or be forecast to affect an area of at least 3000 square miles
at any one time. However, if the total area to be affected during the forecast
period is very large, it could be that only a small portion of this total
area would be affected at any one time.
AIRMETs are routinely issued for 6 hour periods beginning at 0145 UTC
during Central Daylight Time and at 0245 UTC during Central Standard Time.
AIRMETS are also amended as necessary due to changing weather conditions
or issuance/cancelation of a SIGMET.
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