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Interesting report on 9-5-04 Iowa outbreak from NWSFO

September 5, 2004 Tornadoes
Brad Small, Senior Meteorologist, Des Moines NWSFO

A late season tornado outbreak occurred across Iowa during the early evening hours of Sunday September 5, 2004. The environment suggested little potential for large hail and minimal chances of damaging straight-line winds. The greatest severe weather threat was actually tornadoes, and that turned out to be the case. There were eight tornadoes in the Des Moines National Weather Service Forecast Area, all F0 or F1, no reports of hail, and only one straight-line wind report.

The environment reflected high values of both shallow and deep layer shear with only weak to moderate instability.