National Weather Service United States Department of Commerce

Snow in the Great Lakes; Windy Conditions in the East

Lake effect snow will impact the Great Lakes region through the day. Gusty winds will pick up across the Midwest, Northeast and Mid-Atlantic beginning this afternoon following a cold front. Elevated fire weather conditions will persist across the Desert Southwest today, with critical fire weather conditions developing Wednesday and Thursday in the Southern Plains. 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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