Heavy Rain and Mountain Snow Lingers in California; Winter Storm Impacting the Great Lakes and Northeast U.S.

An atmospheric river will wind down through today across California with lingering heavy rainfall, heavy mountain snow, and gusty winds. A wintry mix of freezing rain, sleet, and snow will cause hazardous travel conditions for the Great Lakes into the northern Mid-Atlantic and southern New England today through Saturday morning. Areas of tree damage and power outages are possible. 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)

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Heavy Rain and Mountain Snow Lingers in California; Winter Storm Impacting the Great Lakes and Northeast U.S.

ZSE SIGMETs