AIRMETs
AIRMETs are weather advisories issued for significant weather that does not meet the criteria for a SIGMET.
They are issued every 6 hours.
AIRMET Sierra: IFR or Mountain Obscuration
AIRMET Sierras are issued for:
- Ceilings < 1000' and/or < 3 mi visibility affecting more than 50% of the area
- Extensive mountain obscuration
AIRMET Tango: Turbulence
AIRMET Tangos are issued for:
- Moderate high altitude turbulence (> FL180)
- Moderate low level turbulence (< FL180)
- Low level wind shear (LLWS) below 2000 feet AGL
- Sustained surface winds of 30 knots or more at the surface
AIRMET Zulu: Icing
AIRMET Zulus are issued for:
- Moderate icing
- Lowest freezing levels
- Multiple freezing levels