Damaging Winds in Iowa, July 8, 1999

A very warm and humid airmass was in place over Iowa with surface temperatures in the low to mid 90s and dew point temperatures between 70 and 75. A cold front moved southeast into the state from South Dakota. The airmass over the state was capped and thunderstorms did not develop until the late afternoon hours. A line of thunderstorms developed just ahead of the front. The storms were initially severe west of the Des Moines County Warning Area, though by the time they reached the Des Moines area they had fallen below severe levels. Winds of 30 to 40 MPH were common, along with some small hail and brief heavy rain. One rogue cell moved into the Ames area. The cell weakened as it moved through the city. As it did, a downburst of strong winds swept across the northern part of the city. Trees and power poles were knocked down by the winds. The damage area was fairly small and the storm weakened rapidly after moving through northern Ames. Farther west in Crawford County, thunderstorms rumbled through the Vail area. Though most of the storms were not severe. A strong downburst or outflow from one of the storms in the line derailed three cars of an eastbound intermodal train. The train was near Vail, on the Boone Subdivision. The cars carried 14 empty containers, eight of which were lost off the platforms and damaged. Minimal track damage was reported. Damage was placed at $94,400.