Below is the 12Z GFDL Model Run on Hurricane Ike. This is 96 hours out or 7am Sunday.
I would note, the GFDL is the fastest model on this storm. The NHC has Ike in North Texas Sunday morning. The HWRF model shows Ike in SE Oklahoma Sunday morning. Most other models are the same as the NHC path and the HWRF. But any outlying models have to be taken with some caution. Below is the 12z Model run of the GFS at 7am Sunday. It shows Ike in Texas and no rain in Iowa.
More Model runs will be needed to specify any risk of heavy rain from Ike for Iowa this weekend or later next week.