Snow Squalls May Impact New Year's Eve Travel from the Great Lakes to the Northeast; Heavy Rain Returns to California

An Alberta clipper will bring lake effect snow downwind of the Great Lakes, with the highest snow totals downwind of Lakes Erie and Ontario. Snow squalls may impact New Year's Eve travel during the evening and overnight hours across parts of the Great Lakes, Ohio Valley, and Northeast. Heavy rain will bring a flash flooding threat for southern California on New Year's Eve into New Year's Day. 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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Snow Squalls May Impact New Year's Eve Travel from the Great Lakes to the Northeast; Heavy Rain Returns to California

ZSE SIGMETs