(b)  
freezing precipitation (not requiring a SIGMET);

(c)  
moderate icing;

(d)
 moderate turbulence;

(e)  
thunderstorms (isolated as opposed to a line);

(f)  
an increase in the surface mean wind over a large area to 20 kt or more, or an increase in gusts to 30 kt or more, when no winds were originally forecast; or

(g)  
a difference between the forecast and observed wind direction greater than 60°.

Fr: AIRMET
(2) U.S.: In-flight weather advisories issued only to amend the area forecast concerning weather phenomena which are of operational interest to all aircraft and potentially hazardous to aircraft having limited capability because of lack of equipment, instrumentation, or pilot qualifications. AIRMETs concern weather of less severity than that covered by SIGMETs or convective SIGMETs. AIRMETs cover moderate icing, moderate turbulence, sustained winds of 30 kt or more at the surface, widespread areas of ceilings less than 1000 ft and/or visibility less than 3 mi., and extensive mountain obscurement.