Fix parcel profile on skewT example.
Fix parcel profile on skewT example.

Unidata/MetPy,jrleeman/MetPy,dopplershift/MetPy,ahaberlie/MetPy,ahaberlie/MetPy,dopplershift/MetPy,jrleeman/MetPy,ahill818/MetPy,deeplycloudy/MetPy,ShawnMurd/MetPy,Unidata/MetPy