Showalter Index Calculator

Snow in the Rockies; Showers and Thunderstorms Along the Gulf Coast; Potential Winter Storm for Northern Mid-Atlantic and Interior New England

A winter-like pattern will continue over much of the Lower 48 over the next few days, with snow stretching from the Rockies today into the Middle Mississippi Valley on Monday. Showers and thunderstorms will develop along the Gulf Coast and Southeast on Monday. As the storm moves northward late Monday into Tuesday, winter weather is possible from the Central Appalachians to Interior New England. Read More >

Showalter Index

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What does my answer mean?

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.

Snow in the Rockies; Showers and Thunderstorms Along the Gulf Coast; Potential Winter Storm for Northern Mid-Atlantic and Interior New England

Showalter Index

by Tim Brice and Todd Hall

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What is the formula for the Showatler Index?