National Weather Service United States Department of Commerce

Major Storm System Bringing A Plethora Of Impacts To The Central And Eastern U.S. This Weekend

A powerful storm system will track from the Plains to the Great Lakes region this weekend. On the cold side of the storm, heavy snow with blizzard conditions are expected over portions of the central and northern Plains to the upper Great Lakes. Severe thunderstorms, heavy rainfall, and flash flooding will be possible over the lower Mississippi, Tennessee, and Ohio Valley. 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?