Garmin GI 275 Pilot's Manual page 143

AIRMETs
An AIRMET (AIRmen' s METeorological Information) can be especially helpful for pilots of
light aircraft that have limited flight capability or instrumentation. An AIRMET must affect
or be forecast to affect an area of at least 3,000 square miles at any one time. AIRMETs are
routinely issued for six-hour periods and are amended as necessary due to changing weather
conditions. AIRMETs are displayed as colored, dashed lines.
Icing
Areas of moderate airframe icing including areal extent
Turbulence
Areas of moderate turbulence including vertical extent
IFR
Weather conditions with ceilings <1,000 ft and/or visibility <3 mi
MTN OBSR
Widespread mountain obscuration due to clouds, precipitation, smoke, haze, mist, or fog
Sustained surface winds >30 kt and/or potential non-convective wind shear below
Surface Winds
2,000 ft AGL
SIGMETs
A SIGMET (SIGnificant METeorological Information) advises of weather that is potentially
hazardous to aircraft. In the contiguous United States, the following items are covered: severe
icing, severe or extreme turbulence, volcanic ash, dust storms, and sandstorms that lower
visibility to less than three statute miles.
A Convective SIGMET is issued for the following conditions: thunderstorms, isolated severe
thunderstorms, embedded thunderstorms, hail at the surface, and tornadoes.
A SIGMET is widespread and must affect or be forecast to affect an area of at least 3,000
square miles. SIGMETs are displayed as a yellow-dashed line.
190-02246-01 Rev. A
AIRMET Legend
AIRMET Types
SIGMET
Garmin GI 275 Pilot's Guide
Hazard Avoidance
121