▁event ▁that ▁occurred ▁in ▁the ▁Mid western ▁United ▁States ▁in ▁the ▁third ▁week ▁of ▁August ▁ 2 0 0 7 . ▁While ▁H urr icane ▁Dean ▁was ▁affect ing ▁the ▁Y uc at án ▁Pen ins ula ▁and ▁the ▁G ulf ▁of ▁Mexico , ▁and ▁Trop ical ▁Storm ▁Er in ▁was ▁affect ing ▁Oklahoma ▁and ▁Texas , ▁a ▁persistent ▁storm ▁system ▁hung ▁over ▁the ▁Mid west ▁for ▁several ▁days , ▁causing ▁repeated ▁flash ▁flo oding ▁in ▁the ▁US ▁states ▁of ▁Illinois , ▁Indiana , ▁Iowa , ▁Minnesota , ▁Ohio , ▁and ▁Wisconsin . ▁C ool ▁Canadian ▁air ▁cl ashed ▁with ▁large ▁quantities ▁of ▁warm ▁mo ist ▁air ▁from ▁the ▁G ulf , ▁producing ▁tor r ential ▁ra ins ▁along ▁a ▁station ary ▁front . ▁ ▁E igh teen ▁death s ▁across ▁the ▁central ▁United ▁States ▁were ▁attributed ▁to ▁the ▁resulting ▁flo oding . ▁ ▁Seven ▁Minnesota ▁count ies , ▁eight ▁Ohio ▁count ies , ▁four teen ▁count ies ▁in ▁Wisconsin , ▁and ▁seven ▁count ies ▁in ▁Illinois ▁were ▁declared ▁Federal ▁Dis aster ▁Are as . ▁ ▁Meteor ological ▁syn opsis ▁▁ ▁On ▁Saturday , ▁August ▁ 1 8 , ▁a ▁warm ▁front ▁pushed ▁north ward ▁into ▁Iowa ▁and ▁Illinois , ▁where ▁it ▁became ▁station ary . ▁ ▁W arm , ▁mo ist ▁air ▁pushing ▁over ▁the ▁front al ▁boundary ▁fue led ▁show ers ▁and ▁th under st orm s ▁that ▁moved ▁in ▁a ▁west - to - east ▁fashion , ▁training ▁over ▁the ▁same ▁areas ▁for ▁hours ▁at ▁a ▁time . ▁ ▁Some