Sharp Snowy cutoff

In Chicago, the story is undoubtedly about the snow that fell in the north suburbs, but residents on the Southside will be unimpressed. Places like Hoffman Estates saw 8” of snow, according to the NOAA analysis (seen above) but in Oak Lawn, they only got 2-3” of accumulation. That’s a striking range , influenced by how much cold air could filter into the lower levels as the system, now bothering the eastern Seaboard, pressed through the Windy City.

As the event unfolded, radar indicated a bright streak on the radar, called “bright banding” which indicated precipitation heavy enough to resemble rain on radar. In fact, this band of precipitation from the north side of Chicago to southeastern Iowa was producing a fair amount of lightning as well. The problem for residents under this narrow swath was that all the precipitation was falling as snow. Very heavy snow.

The band was at the northernmost end of the storm, which means there was no transition to rain or sleet to account for, so we could see in striking accuracy how heavy this band was. In Iowa City, there were 8″ of snow, but just half a mile to the north in Cedar Rapids, no snow reached the ground! 

This is a more common analysis than you might think, particularly with strong systems in the transitional seasons. Heavy snow never seems to cover as much territory as we seem to think when we’re smack dab in the middle of it.