The chart below can be used to gain a greater understanding of what numerical values of CAPE indicate as it relates to convection of air parcels. Remember, CAPE is only the potential energy. High CAPE values cannot be used as a predictor about whether or not severe weather is going to take place at a given time or that severe weather is looming.
CAPE value Convective potential
0 Stable
0-1000 Marginally Unstable
1000-2500 Moderately Unstable
2500-3500 Very Unstable
3500 + Extremely Unstable