Above is the NAM Relative Humidity/Lifted Index (4 panel Forecast), also see the
full size images in 6 hour increments.
LI > 2 No significant activity
0 < LI < 2 Showers probable, isolated thunderstorms possible
-2 < LI < 0 Thunderstorms probable
-4 < LI < -2 Severe thunderstorms possible
LI < -4 Severe thunderstorms probable, tornadoes possible
