AIRMET

An Airmen's Meteorological Information advisory issued for weather phenomena that may be hazardous to light aircraft and VFR pilots, but are less severe than SIGMET conditions. AIRMETs cover moderate icing (AIRMET Zulu), moderate turbulence or sustained surface winds of 30 knots or more (AIRMET Tango), and IFR conditions or mountain obscuration (AIRMET Sierra). They are valid for six hours.