Showalter Index Calculator

Severe Thunderstorms and Heavy Rainfall in the Ohio Valley and Great Lakes; Winter Weather in the Northern Tier

A slow moving front extending from the Great Lakes region into the Plains will bring snow, wintry mix, and ice accumulation north of the front from the Upper Midwest into New England, and severe weather and heavy rain south of the front. Scattered severe thunderstorms with damaging gusts, severe hail, and heavy rain are expected across parts of the Great Lakes/Midwest through tonight. Read More >

Showalter Index

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Showalter Index greater than 0: Stable, but weak convection possible for SI = 1-2 if strong lifting is present.
Showalter Index between 0 and -3: Moderately unstable.
Showalter Index between -4 and -6: Very Unstable.
Showalter Index between less than -6: Extremely Unstable.

Severe Thunderstorms and Heavy Rainfall in the Ohio Valley and Great Lakes; Winter Weather in the Northern Tier

Showalter Index

by Tim Brice and Todd Hall

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What is the formula for the Showatler Index?