Why ‘clear’ road conditions may be deceiving over the next couple of days
COLUMBIA, Mo. (KMIZ)
After the recent snowstorm, roads are starting to see relief across much of Central Missouri. But these looks can be deceiving, as there may still be lingering dangers on the roads that could lead to you losing traction. This threat is known as black ice.
Black ice is a very thin layer of ice that accumulates on pavement that is below 32 degrees Fahrenheit, which is below freezing. Due to the fact that this layer of ice is so thin, the transparency helps the ice blend in with the dark pavement, making it difficult to see. The three most common ways this occurs are due to snow melting during the day, freezing rain, or mist/drizzle that freezes on impact with surfaces below freezing. For snow melting during the day, it refreezes overnight when temperatures drop back below freezing. Freezing rain occurs as the liquid rain falls onto surfaces that are also below freezing, leading to freezing on impact.
In Central Missouri's case, black ice is being caused by snow melt during the day. Yesterday, the 28th, temperatures near and south of I-70 all rose above freezing in the afternoon, which helped accelerate snow melt across the area. During the overnight hours, temperatures quickly fell back into the teens, which is well below freezing. This means that any snow melt that did occur on roadways froze back over, which could've led to slick spots on your morning commute.
You also may have noticed that earlier in the week, when temperatures were still well below freezing during the day, melting of snow was still occurring. This was because of the persistent sunshine that was present during those days. As the incoming solar radiation is received by the Earth, darker surfaces begin to absorb that radiation. Although not as much radiation is absorbed, this also occurs with the leftover snow across the area. These surfaces begin to emit their own radiation, which goes into heating a very thin layer of air just above the surface of the Earth. Although this is not effective enough to significantly heat the surrounding air above this layer, it is enough to warm temperatures up enough in this thin layer of air to the point where snow melt can occur. Once the sun sets, this snow melt can re-freeze and become black ice in a short amount of time.
There are a couple of ways to stay safe when driving if you potentially run into this black ice. First, reducing speed if you suspect black ice may be present will help lessen the likelihood of losing traction. Second, avoiding sudden stops is important, as that action can cause the tires to slip instead of slowing the car down. If you are in the act of sliding, turn the wheels in the same direction you are sliding rather than turning in the opposite direction. This aligns the tires with the vehicle's momentum, which allows them to stop sliding and start rolling again. Finally, if you are unsure about any roadways, hills, or steep inclines, it is better to avoid the roadway and choose a different route.
