Watch this 16-day National Weather Service GFS model upper air (jet stream) forecast animation at the 500 mb. level (roughly 18,000 ft.) and the troughs which begin digging into the central and eastern U.S. in the 1-2 week range. While none is YET forecast to generate a storm system likely to DIRECTLY impact Chicago, this IS A PATTERN SHIFT which suggests deeper penetration of cold air surges into the eastern and central U.S. and a more favorable pattern for storm development. The morning GFS en