• A conditionally unstable atmosphere
(high CAPE).
•Warm
moist air in the lower troposphere.
•Dry
cold air in the middle troposphere.
•Over
the Great Plains, where supercells
are most common, the moist airmass typically
originates over the Gulf of Mexico, while the dry
airmass originated over the mountain to the west.
•These
two airmasses are separated by a capping inversion.