• Instrument Flight Rules (IFR) or Mountain Obscuration - AIRMET SIERRA (6-hour period)
  • Ceilings less than 1000 feet and/or visibility less than 3 miles affecting over 50% of the area at one time.
  • Extensive mountain obscuration

Webmaster
US Dept of Commerce
National Oceanic and Atmospheric Administration
National Weather Service
Oakland Center Weather Service Unit
5125 Central Ave.
Fremont, CA 94536-6531