* WHAT...Dangerously cold wind chills of 30 to 35 below expected.

* WHERE...The northern half of Iowa.

* WHEN...Until noon CST Tuesday.

* IMPACTS...The dangerously cold wind chills could cause frostbite on exposed skin in as little as 10 minutes.

* ADDITIONAL DETAILS...Wind chill values will rise quickly late Tuesday morning and by afternoon wind chills of 5 to 15 below will be common.