This loop of GOES-8 6.7 micrometer InfraRed (water vapor) imagery shows the rapid eastward progression of an upper-level shortwave trough across Nebraska, Iowa, and the southern Great Lakes region. Note the area of warming brightness temperatures (dark gray to black enhancement) in the wake of the departing shortwave -- this warming signaled a region of mesoscale subsidence and drying within the lower to middle troposphere, which moved east-southeastward across southern Minnesota and southern Wisconsin during the afternoon hours on 29 March 1999.