Synoptic-scale environments favorable for producing derechos in the cool se
ason (September through February) are examined with the goal of providing u
seful techniques for identifying commonalities within derecho activity corr
idors. Fourteen derechos were identified from two activity corridors locate
d in the southeastern United States and Atlantic seaboard regions between 1
986 and 1995. The synoptic environment at the initiation and midpoint of ea
ch derecho was then evaluated using surface, upper-air, and the NCAR/NCEP r
eanalysis data sets. Models are provided in order to illustrate the synopti
c-scale environment and to assist meteorologists in recognizing conditions
favorable for cool-season derecho formation. Marginal instability and stron
g synoptic-scale forcing characterized the environments of events in both c
orridors. The overall synoptic patterns associated with cool-season derecho
-producing mesoscale convective systems (DMCSs) resembled environments foun
d with cool-season tornado episodes. Recognition of key elements in this en
vironment could lead to improvements in cool-season severe weather predicti
on.