WINDSHIELD WASHER ALERT: Freeze Thaw Cycle Ahead - KMSP-TV

WINDSHIELD WASHER ALERT: Freeze Thaw Cycle Ahead

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Chances are you have heard of, and are excited about, the above freezing temperatures in the forecast. The warm temps will not only make it pleasant to be outside but they will also make for a mess on the roadways. Melting snow, splash back and nightly re-freezes will have us going to "Wide open" to "Super cautious" over the week ahead. All Season long the roads have seen more salt than a bag of chips. The salt has been in place all winter season, along with some brutal temperatures. Now that there are more manageable temps in the forecast, that salt is going to get the shot in the arm it needs to live up to its potential.

Road salt works by lowering the freezing point of water. We all learned in science class that water freezes at 32°, and that is still the case today…LOL! When salt is added to water, it lowers the freezing point. Water with a salt content of 10% will now freeze at 20° and water with a salt content of 20% will now freeze at 2°. When salt is added to roadways it works its way into the ice, raising the salinity of the liquid and lowering the liquid's melting point. You may be asking yourself, why does the salt stop working when it is very cold? We asked that question a lot this winter and the answer is simple. When the road surface gets to 15° or colder the salt can NOT make its way into the ice to do its magic, therefore salt and ice are like a dormant winter seed, waiting for a hint of warmth to wake up and do theor thing.

WHY DO BRIDGES FREEZE OVER FASTER?

This is a common question with a simple answer. Bridges are elevated, obviously, and that allows for air to circulate around them. Most bridges are mode of asphalt or concrete which are both poor conductors of heat. Long story short, this will allow the bridge surface temperature to closely mirror the air temperature.

The roads have insulation from the earth, so the surface temperature will take longer to fall in cold weather. That magical number of 15° will come into play over the next few days as we see daytime highs in the 20s and lows in the single digits. Bridges will play the "Freeze Thaw" game through the weekend. They will be just fine in the daytime and then turn icy at night.

We would love to see your weather photos! Email them to Photos@Fox9.com . Also I hope you will LIKE my Facebook page https://www.facebook.com/#!/SteveFrazierFox9Kmsp and follow me on Twitter @frazierfox9. Thanks for watching! FRAZIER

 

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