National Weather Service United States Department of Commerce

Quiet Weather Pattern for U.S. Today; Cold Front to Move into Pacific Northwest Tonight

Expansive Canadian-sourced high pressure will provide mainly fair weather across the U.S. on Monday. Temperatures over the eastern states will run below normal while the western states see above normal temperatures. On Monday night, a cold front will move onshore in the Pacific Northwest, bringing low elevation rain and heavy mountain snow; unsettled weather will continue through the week. Read More >

 

Icing Convective Turbulence
Icing SIGMETs Convective SIGMETs Turbulence SIGMETs
IFR Volcanic Ash All
IFR SIGMETs Volcanic Ash SIGMETs All SIGMETs

Text of all CONUS SIGMETs

Description of Convective and Non-Convective SIGMETs

SIGMETs are Inflight Weather Advisories for Significant Meteorological hazards. A SIGMET is "widespread" in that it covers an area of at least 3,000 square miles. Note that the particular hazard may be present in only a small portion of the area at any particular time. SIGMETS are issued for:
  • Severe Icing (not associated with thunderstorms -- otherwise, it is a Convective SIGMET)
  • Severe Turbulence (similarly, only if not associated with thunderstorms)
  • Duststorms and sandstorms lowering visibility to less than three miles
  • Volcanic Ash

Convective SIGMETs are issued for severe convective activity, which implies severe turbulence, severe icing, and low-level wind shear. Specifically:
  • Embedded thunderstorms
  • A line of thunderstorms
  • Thunderstorms with heavy precipitation affecting 40%+ of an area at least 3,000 square miles
  • Surface winds 50+ knots due to severe thunderstorm
  • Hail 3/4+ inches in diameter
  • Tornadoes