National Weather Service United States Department of Commerce

Heat Wave in the Eastern US; Heavy Rain in the Ohio Valley

Dangerous, long-lasting heat is expected across portions of the Central and Southeast U.S. Showers and thunderstorms, some severe, may produce heavy rain and localized areas of flash flooding across parts of the Ohio/Tennessee Valleys into the Appalachians. Severe thunderstorms are possible across parts of the northern Great Plains. Fire weather conditions possible in the Great Basin. Read More >

 

 

 


Text of all SIGMETs Around Contiguous Western US

None Found
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


Map of SIGMETs (including International)