What the map shows
Negative values mean unstable air; −6 or lower is very unstable.
How to read the colors
Warm colors for negative (unstable) values.
Common mistakes
- Using it alone; it ignores the cap and shear.
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Learning Center / Model Parameters / Severe Weather
Surface-Based Lifted Index
A quick instability check comparing a rising parcel with the air at about 18,000 ft.