EF2 tornado in Monona County, Iowa

This tornado continued from Thurston County in northeast Nebraska and into Monona County. The damage in Monona County was generally confined to soft wood trees, but one farmstead did receive minor out building damage. The EF2 damage occurred as the tornado crossed 100th street were several power poles were snapped off at the base. The tornado then exited Monona County into Woodbury County.

The same powerful storm system that produced severe weather across eastern Nebraska on October 3rd remain in the area on the 4th. A strong area of low pressure moved from eastern Colorado into southern South Dakota during the day. As this occurred, a dry line was sweeping across central and into eastern Nebraska. A warm front continued to lift north into northeast Nebraska and western Iowa by late afternoon. With unseasonably warm and moist air in the region the atmosphere became strongly unstable. This instability coupled with a strong wind field associated with the powerful storm system and created and environment favorable for significant severe weather. Supercells developed near the intersection of the dry line and warm front over northeast Nebraska during the afternoon and tracked northeast. The supercells were responsible for large hail, damaging winds, and significant tornadoes. Other isolated thunderstorms developed south along the dry line into western Iowa producing very large hail and damaging winds during the evening of the 4th.