Everyone who lives near a great lake knows about lake-effect snow. The Great Lakes seldom freeze entirely over, and create more-or-less permananent reservoirs of relatively warm, moist air over the lakes. When prevailing winds move this moist air over the colder land, the moisture precipitates out as snow, which is why areas such as western New York state, western lower Michigan, and the southwestern shores of Lake Superior are notorious for heavy snow accumulations. In Milwaukee, we get lake effect snowstorms when the winds are out of the east to northeast, which conditions can sometimes last for days.
Saturday and Sunday, we had moist upper air masses moving off the lake and dumping rain on the city, but in a very odd fashion. There was almost no wind at ground level, but the intensity of the rainfall varied from light drizzle to utter deluge, sometimes within a couple of blocks. Some areas got no rain while others were being poured on. Three waterspouts were observed off the coast on Saturday. Georgie and I agreed that we hadn't seen the like since we had been living in Milwaukee--in my case, almost thirty years.
EDIT: Per the newspaper weather column, what we have been having is called a "cut-off" low pressure center. So it is a defined phenomenon, although still rare.
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