Intense lake-effect snows hit sections of the Chicago metro area hard and fast Wednesday evening with whiteout conditions embedded with flashes of lightning and crashes of thunder, which continued sporadically over several hours. Thunder and lightning occur as air rushes aloft. This upwelling encourages air to sweep into the system concentrating moisture which leads to especially vigorous snowfall.
From Kenosha to Waukegan, Gurnee, Skokie, Mt. Prospect, Oak Brook and Batavia south to Bolingbrook, Ottawa, Joliet and Palos Heights—and, across the city of Chicago—snow fell furiously and accumulated in a matter of just hours to as much as 6 to 8 inches. Late evening traffic slowed to 10 mph on the snow-covered Kennedy Expressway (I-90) and the Reagan Memorial Tollway (I-88). Preliminary totals by late Wednesday evening, with snow still falling at some locations, had reached nearly 8 inches at Gurnee and near Golf and Busse Roads in Mt. Prospect, 6.2 at Beach Park, 6.0 at Zion, 4.3 at Oak Brook and 4.0 at Bolingbrook, Des Plaines and Northbrook.
An inch of snow had fallen at O’Hare by 8:30 p.m. Wednesday, with snow still coming down hard. That was enough to push the city’s official seasonal snow tally above 50 inches for the third consecutive year. There’s been only one other string of three consecutive 50+ inch seasons in 125 years of snow measurements here and it occurred between 1976 to 1979.
Lake effect snows occur in especially cold environments which, because of the efficiency of ice crystal formation at low temperatures, frequently produce larger than typical accumulations from the limited amount of water vapor available. This leads to snowflakes which exhibit maximum “fluff”. Estimates of Wednesday’s snow puts snow/water ratios at 30 to 1—indicating the system’s snowflakes had almost three times the volume of those which come down in more typical 10 to 1 ratio snow events. One witness, in describing the rate of snowfall in Evanston, compared the scene to a “snow globe.” Another described “pure whiteout conditions with snow coming in horizontally” and still another characterized the snowfall intensity at its height Wednesday evening as “this season’s heaviest.”
A “meso-low” over Lake Michigan–a compact area of low pressure which, when enriched with lake moisture is capable of producing intense bursts of snowfall like those observed here Wednesday evening—first appeared east of Door County Tuesday evening. The system proceeded south the length of the lake Wednesday sending bursts of heavy snow into the Milwaukee area in the afternoon resulting in local 4 to 4.5-inch totals.
Northeast braces for hurricane-intensity winter storm
Barometric pressures over the western Atlantic east of Florida Wednesday were in free-fall. A developing northbound storm system was predicted to intensify explosively before reaching the mid-Atlantic Coast near New York late Thursday and stalling. The storm was behind the maze of weather watches and advisories which had been issued late Wednesday spanning sections of 34 states. New York City, with 30.5 inches of snow on the books this season (17.9 is normal) and Philadelphia with 73.1 (13.8 inches is normal by this date) are among the areas threatened with significant accumulations after a switch from heavy rain to snow. Mountainous areas from Pennsylvania across Upstate New York and New England, may measure snow in feet before this storm finally departs. And powerful east winds on its north side are likely to send clouds and light snow westward as far as eastern Illinois and Wisconsin by the weekend.