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Dangerous Cold Weather for Most of the Country; Rare Winter Storm for the South; Fire Weather Concerns for Southern California

Arctic air will filter south and east through early this week. As this cold air moves across the South, a rare winter storm is forecast to develop from Texas, Gulf Coast States into the Southeast through early this week. Several new daily record low temperatures are expected, including new record-low maximum temperatures. For Southern California, fire weather concerns increase this week. Read More >

Seattle, WA

Center Weather Service Unit

ZSE SIGMETs

Weather.gov > Seattle, WA > ZSE SIGMETs

 

 

 


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)

 

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