Iowa DOT "black ice" warning - KWWL - Eastern Iowa Breaking News, Weather, Closings

Iowa DOT "black ice" warning

AMES (KWWL) -- The Iowa Department of Transportation (DOT) is warning drivers that the combination of atmospheric conditions, falling pavement temperatures and occasional blowing snow is suitable for the formation of black ice and/or refreezing of moisture on roadways and bridges later this afternoon through the overnight hours. Even when the pavement appears to be mostly dry or just wet, roads could be deceivingly slippery in spots.

When the mercury drops below 25 degrees F, road salt's effectiveness as a deicer begins to diminish. Normally, 15 to 20 degrees F is considered the lower limit for salt.

The National Weather Services' winter weather advisory will remain in effect into this evening for portions of central and eastern Iowa. An additional 1 to 3 inches of snow is possible in these areas.

Black ice isn't really black. It's so thin and transparent that the underlying color of the pavement shows through, making the surface appear to be wet or even clear and dry. A driver may not realize there is an icy road surface until their vehicle begins to slide.

Black ice most commonly forms on roads around bodies of water (such as lakes and rivers), in rural areas, and on bridges and overpasses, but it can form unexpectedly on any road surface. It can also form on gravel roads, as well as hard-surfaced roads.

On heavily traveled roads, such as the interstates, light blowing snow over warm vehicle tire tracks can also stick, causing slick conditions.

Click here for tips on driving in icy conditions.

The Iowa DOT will be monitoring road conditions and issuing additional alerts, as warranted. For the latest road conditions, visit on the Internet or call 511 (for outside the state or in bordering communities, call 800-288-1047).

Online Producer:  JJ Murray

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