An atmospheric index specifically designed to he related to the growth
of wildland fires is evaluated for two recent Idaho fires. The index
includes terms related to high midlevel lapse rates and low-level dry
air. In the cases examined, the index performs well at pinpointing the
time of the most explosive fire growth. Long-term season statistics a
lso show that the index is useful for determining when the most acreag
e will be lost to wildland fires.