[18] By 1:00 p.m. CDT (12:00 p.m. CST; 18:00 UTC) on April 30, a low-pressure area of at most 984 millibars (29.06 inHg) was centered near Pierre, South Dakota, with a stationary front superimposed from north of Sioux Falls to near LaCrosse, Wisconsin.

Nearby, a warm front also attended from south of Sioux Falls to near Des Moines, Iowa, and St. Louis, Missouri.

[19] As the warm sector advanced into northernmost Iowa and southern Minnesota, surface air temperatures rose into the 60s and low 70s °F, while dew points reached the 60s °F.

[19] By 7:00 p.m. CDT (6:00 p.m. CST; 00:00 UTC), the warm front migrated to near the Minnesota-Iowa border, while the mid-level trough associated with the surface cyclone acquired a negative tilt.

At the same time, a strong jet stream brought deep-layer wind shear over portions of northern Iowa and southern Minnesota—indicating favorable conditions for tornadogenesis.