Listed below are the values of several stability indices and their typical interpretation. It should be noted that these index values provide a relative potential for thunderstorm occurrence based on the stability index alone. These relationships were developed when it was believed that stability indices alone could tell you the potential for thunderstorms. Recent research in thunderstorm forecasting has shown that instability is a necessary but not sufficient condition for the occurrence of thunderstorms. As a result, index values, by themselves, are only a part of the total evaluation needed to forecast thunderstorms. Use these tables with care.
| Index Value | Thunderstorm Indication |
| 0 to -2 | thunderstorms possible good trigger action needed |
| -3 to -5 | unstable thunderstorms probable |
| less than -5 | very unstable heavy to strong thunderstorms possible |
source: reference 1
| Index Value | Thunderstorm Consideration |
| 3 to 1 | thunderstorms possible strong trigger needed |
| 0 to -3 | unstable thunderstorms probable |
| -4 to -6 | very unstable good heavy thunderstorm potential |
| less than -6 | extremely unstable good strong thunderstorms potential |
source: reference 1
| West of Rockies | East of Rockies | Thunderstorm Probability |
| less than 15 | less than 20 | none |
| 15 to 20 | 20 to 25 | isolated thunderstorms |
| 21 to 25 | 26 to 30 | widely scattered thunderstorms |
| 26 to 30 | 31 to 35 | scattered thunderstorms |
| above 30 | above 35 | numerous thunderstorms |
K values may not be representative of an airmass if the 850 mb level is near the earth's surface. Western United States values are forced to approximate areal coverage used by George [2].
source (west of Rockies): reference 1
source (east of Rockies): reference 2
| Vertical Totals (VT) | |
| VT Values | West of Rockies with adequate moisture |
| less than 28 | no thunderstorms |
| 29 to 32 | few thunderstorms |
| more than 32 | scattered thunderstorms |
source: reference 1
| Total Totals (TT) | |
| VT Values | West of Rockies |
| 48 | isolated or few thunderstorms |
| 52 | scattered thunderstorms few of moderate intensity |
| 55 | scattered thunderstorms a few moderate, isolated severe |
| 58 | scattered moderate thunderstorms few severe, isolated tornadoes |
| 61 | scattered to numerous moderate thunderstorms few to scattered severe, few tornadoes |
| 64 | numerous moderate thunderstorms scattered severe thunderstorms scattered tornadoes |
source: reference 1
| East of the Rockies | |||
| CT Values | VT Values | TT Values | Forecast |
| 18-19* | 26 or more* | 44 | isolated or few thunderstorms |
| 20-21 | 26 or more | 46 | scattered thunderstorms |
| 22-23 | 26 or more | 48 | scattered thunderstorms isolated severe |
| 24-25 | 26 or more | 50 | scattered thunderstorms few severe, isolated tornadoes |
| 26-29 | 26 or more | 52 | scattered to numerous thunderstorms few to scattered severe, few tornadoes |
| 30 | 26 or more | 56 | numerous thunderstorms scattered severe, scattered tornadoes |
* along the immediate Gulf Coast and over the Gulf Stream, CT of 16 or more and VT or 23 or more
TT is the most important.
source: reference 3
[1] Western Region Technical Attachment, No. 84-14, May 1984, National Weather Service, Salt Lake City, UT.
[2] George, J.J., 1960: Weather Forecast for Aeronautics. Academic Press, New York.
[3] Miller, R.C., 1972: Notes on Analysis and Severe Storm Forecasting, Procedures of the Air Force Global Weather Central, AFGWC Technical Report 200 (rev).