The K-Index serves as an acid test regarding thunderstorm potential. The K-Index considers the amount of instability between 850 MB and 500 MB, the absolute amount of moisture at 850 MB and the amount of moisture relative to temperature at 700 MB. In general, values of less than 20 are considered unfavorable for thunderstorm development, whereas values over 40 suggest very high potential for thunderstorm development. However, the K-Index must be used with care as low-level atmospheric conditions (below 850 MB) are disregarded.