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Apologies in Advance - RonO's Ramblings

Dec. 9th, 2009 12:05 pm Apologies in Advance

Reading the reports of snow covering various portions of the mid-west (from Iowa to Michigan) and other nasty weather further east (sleet in Pennsylvania), is once again reminding me of one of the reasons I didn't mind all that much moving from near Chicago to San Diego a year-and-a-half ago.

On the other hand, listening to and witnessing how people in dry warm-weather climates, or at least people in this one, seem to panic just as hard over a little bit of rain on the roads, makes me almost wonder if snow wasn't worth it. At least snow stays slippery as long as its coming down, and ice is almost always slippery.

Unless roads out here are different from everywhere else I've heard about, after an hour or so -- depending on how quickly the rain falls -- the oils that collect on the road have washed off. Once the oils have washed away, wet roads are not much more, or even less, slippery than dry roads (at least as long as the water remains in its liquid phase).

There are still two risks. First, while there is still oil floating on top of the thin layer of water, roads are as slippery as they are with a layer ice, or untreated snow. Second, if the water layer is thick enough, and the vehicles tires lack sufficient grooves, the tires can fail to make contact with the actual road surface. This second effect is aggravated by speed.

Now when the rain exceeds, or reaches, the local capacity for handling run off (like it did here on Monday), that can cause a problem as well. But snow also produces run off, and ice can actually reduce the capacity for run off in certain situations. (I recall that the Des Planes River flooded a few years back largely because of "Ice Dams." (If I'm wrong about this, I'm sure that lonotter will correct me.))

At least I'm not hearing "the world is ending" panic over the rain that is predicted for tomorrow and over the weekend. I'm just regretting that it will probably be raining for the last weekend this year I might be able to do something outdoors, not that we don't have indoor plans at least for Saturday evening and our usual Sunday morning plans.

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From:lonotter
Date:December 9th, 2009 10:06 pm (UTC)
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I'm not sure if it was ice jams on the Des Plaines, but they've been a problem on other area rivers.

As for rainfall washing off oil, etc., the usual estimate that it happens in the first 15 minutes or so. An hour would only be for a very light rain.