It’s a bumpy day for air travel across portions of the western United States; the National Weather Service’s Aviation Weather Center has issued a “SIGMET” for severe turbulence over portions of California, Oregon, Nevada, Arizona, and Utah. These alerts would impact many passengers on trans-continental routes and those traveling to places like San Francisco, Los Angeles, Las Vegas, Reno, and Salt Lake City.
A SIGMET advises of weather, other than convective activity, that is potentially hazardous to all aircraft. SIGMETs are typically issued for the continental United States and adjacent coastal waters for severe icing, severe or extreme turbulence, dust storms and/or sand storms lowering visibility to below 3 miles, or volcanic ash. These SIGMET items are considered to be widespread because they must be affecting or be forecast to affect an area of at least 3000 square miles at any one time. However, if the total area to be affected during the forecast period is very large, it could be that only a small portion of this total area would be affected at any one time. SIGMETs are issued for 6 hour periods for conditions associated with hurricanes and 4 hours for all other events. If conditions persist beyond the forecast period, the SIGMET is updated and reissued. Convective SIGMETs are issued hourly for thunderstorm-related aviation hazards.
The National Weather Service said windsheer associated with the jetstream is responsible for today’s turbulence.