* WHAT...For the Cold Weather Advisory, very cold wind chills as low as 18 below. For the Extreme Cold Warning, dangerously cold wind chills as low as 27 below expected. * WHERE...Portions of north central, northeast, and northwest Ohio and northwest Pennsylvania. * WHEN...For the Cold Weather Advisory, until 7 PM EST this evening. For the Extreme Cold Warning, from 7 PM this evening to 10 AM EST Wednesday. * IMPACTS...The cold wind chills as low as 25 below zero could cause frostbite on exposed skin in as little as 30 minutes. Frostbite and hypothermia will occur if unprotected skin is exposed to these temperatures. An extended period of freezing temperatures could cause ruptured water pipes. Wind chill values can lead to hypothermia with prolonged exposure.