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You have to love the hoar frost tonight! Took the wife to Epply in Omaha for her flight out to California, the freezing rain and now super hoar frost is taking trees down everywhere! Was held in traffic for all the tree crews out clearing the highway, there wasn't that much freezing rain- so the first for me to see whole trees toppled by frost. Looked like the crowns of all the trees had 6 inch balls of frost around every twig!
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I think around here, rime ice is more common than hoar frost, but more common than both is just plain freezing rain.
But we get something that looks like the hoar frost, but instead of forming on objects above ground, it forms on the ground, and grows upward, like microcrystaline stalagmites. I've never heard of a name for these things, but they seem to form in areas where the water table is very close to the surface, and there is a lot of moisture in the ground, but the air above the ground is very cold, colder than the ground, and when the water vapor escapes from the ground, it crystalizes when it hits the cold air. These little crystal formations sometimes get like 6" tall, so thick that they pretty much cover the ground, and they sort of crunch when you walk on them. Pretty neat.
But around here, the thing that brings down trees is the freezing rain. Usually happens after an extended period of very cold weather, followed by a storm passing us a bit to the west, bringing warm rain up from the south. Usually it will stay right at the freezing point, sometimes for more than a whole day, while the rain instantly freezes as it hits trees, and builds up solid ice cubes on every twig, that can be more than an inch thick. We get these a lot, but the worst one was back somewhere around 1998 or so. The thing that impressed me, was not so much that they would bring whole trees down, but the speed at which limbs would come off big trees. After the ice storm hit, you'd hear what sounded like shotgun blasts going off in the woods, followed by a crash accompanied by an almost musical sound of all the little ice cubes bouncing around. It was big branches snapping off the trees. The thing is that it would just be SNAP and freefall, not a slow cracking sound associated with the branches breaking and bending and the split going parallel to the branch. These branches were so cold from the cold weather that they were brittle and snapped all at once and were free. They fell horizontally, not twig end first.
The dangerous thing about that, was that normally if a limb breaks, you have time to run away, these things snapped, and it was like 2 seconds and they were down. I went out for a walk, and when a couple of these monster limbs came down near me, SNAP-CRASH, I quickly decided that I was going back inside where it was safe.
Usually, the trees aren't quite so frozen, and just bend over to the ground and split, but this one bad year, we had sub-zero weather for about a week, then a day of heavy freezing rain, followed by sub zero weather again, so the tree limbs were completely frozen and brittle. It was really wierd living here in the woods, with no power (for 8 days), so it was real quiet, except for the sound of these tree limbs coming down every few minutes. I think the storm that hit us here, went up into Canada, and they got it even worse, since it brought down their big high voltage power lines.
Sorry this got off topic, but the talk of ice always gets me going. I don't mind a 2' snowfall, but when I hear that potential freezing rain is coming, it really get's my attention. I also like to keep an eye on the temperatures at Mt Washington, NH near here. When the temp up at the top of the mountain is warm, and it's cold down where we live, and rain is forecast, usually there is trouble coming.