Why is School Closed One Day and Not the Next?

As you can probably imagine, school closings are not an exact science. There are many variables that go into the decision. Besides poor road conditions, drifting snow, we have had extreme cold/wind chills the last few days. So why wasn't school closed today (Wednesday)? For our area, the National Weather Service has issued a Wind Chill Advisory, compared to a Wind Chill Warning on Monday and Tuesday. Again....it's far from an exact science but I hope that helps explain the decision making process a little.