National Weather Service United States Department of Commerce

Snow Shifting to the Northeast; Heavy Rain Returns to the South; Blizzard Conditions in Alaska; Monsoon Tough Impacts American Samoa

A storm will slide across northern New England Tuesday with locally heavy snow and ice. Further south, heavy rain and additional flooding is possible from Texas to South Carolina. In Alaska, strong winds and heavy snow will continue Tuesday with localized Blizzard conditions around Bethel. A strong monsoonal trough will continue to pass over American Samoa through Wednesday. Read More >

Showalter Index

by Tim Brice and Todd Hall
 
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Enter the 500 millibar parcel temperature: °C Answers:
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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.

 

What is the formula for the Showatler Index?