JOPLIN, Mo. — Too many days without rain, or at least any significant widespread rainfall, ended up creating hazardous driving conditions in the Four States.

The area is finally seeing enough water that it’s not immediately disappearing due to rapid evaporation.  We have been suffering through an extended drought, where our concerns have been focused on the negative impact on vegetation and groundwater, as our water table steadily drops with each passing day. But when no substantial rain is available for “street cleaning,” the focus changes.

During the past several months, motor oil and other fluids that occasionally escape from vehicles, along with tire debris has been accumulating on area roads. The oil, while not much of a problem, in minor drip and drop fashion during a dry period, becomes a much greater problem when combined with a nice coating of freshly falling rain. (Ask California residents about this particular meteorological/transportation situation.)

The danger is higher during the onset of a rain producing frontal system, because just enough water has accumulated to spread the oil over increasingly larger sections of roadway, causing slick conditions. Later in a rainfall event, following a period of drought, the threat diminishes to some degree, as the slippery oil becomes diluted when water continues to accumulate on the road surface.

Gravity also helps by pulling the slippery stuff off the roads during a prolonged event.

Another meteorological factor played a role in the slip and slide demolition derby in the Four States today – wind. The extremely tight gradient of pressure between our approaching western U.S. low and the eastern states high pressure system, which stayed in the same position for about four days; generated a tremendous amount of wind through the entirety of this past weekend.

That strong southerly flow pulled several tons of leaves off trees and bushes and deposited a fraction of that tonnage onto area roads. The combination of wet leaves glued to road surfaces via molecular attraction exacerbated the problem by reducing the coefficient of friction even further.

The good news is that by the time we get into the second part of our early week rainfall event, which moves in behind our cold front producing even more water on road surfaces, later tonight into Tuesday, most of that oil will have been washed away. Stay safe out there!