Pothole alert

As we mentioned in a Sunday story, the arrival of this long-awaited thaw may be just what your car doesn't need after a rough spell of winter.

The pothole virus is likely to spread this week as temperatures fall back below freezing tonight and zoom toward April levels later in the week.

If it just stayed cold all the time, potholes wouldn't be a problem, but the thawing process is murder on the roadbeds.

Moisture has been seeping into those insidious cracks, and if you've ever had a leaky roof you know that moisture needs no invitation.

The moisture-laden base beneath the road bed expands when it is frozen, and then sinks when it thaws. That weakens the overlying blacktop, which takes beating from the traffic.

On its website the Minnesota Department of Transportation has a tidy summary of the pothole process.

One other factor that speeds the thawing process is the increase in solar energy in February, notes the department's Gene Lorentz.

Of the energy the sun gains from the winter to summer solstice, 36 percent of it occurs in February, according to Fred House, a Drexel University expert on solar radiation.

Blacktop is an excellent medium for soaking up the sun, and the temperatures at the road surface can be significantly higher than the air temperatures.

In short, be careful out there.

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