A strong low-level (between 2000 – 5000 ft) 60 to 70 mile-per-hour jet stream will roar overhead Monday, and with temperatures warming well into the 40s, some of those strong winds could work their way down to the surface. As a cold front approaches and rain spreads over the area from the west, the combination of mild atmospheric-mixing temperatures and increasing pressure gradient could produce wind gusts here well above 40 miles per hour – perhaps even 50 miles per hour in some locations. As the center of low pressure moves east across northern Wisconsin – producing Blizzard and Winter Storm Warnings in North Dakota and Minnesota in it’s wake, the associated cold front will pass through Chicago by early evening. Overnight here winds will shift to the west and northwest with falling temperatures – rain will change over to light snow or snow flurries.
Much colder Tuesday-Wednesday
The upper-level jet stream flow will become northwesterly Tuesday, once again allowing frigid arctic air to flow out of northern Canada into the Midwest and Great Lakes. With the core of coldest air situated just north of Lake Superior, Chicago will be situated close to the center of the arctic high pressure with Tuesday’s highest temperatures occurring early in the morning followed by slowly falling readings along with single-digit wind chills during the daylight hours. The cold will be tempered only slightly Wednesday with the high pressure giving way to potentially significant winter storm development in the southern plains - as the upper air jet stream flow again becomes southwesterly.
Computer models are still sorting out all the potential variables – coming up with various solutions in a very complex process, but indications are an intense low pressure system will track out of the southwestern United States and move through the Midwest, Great Lakes and Ohio Valley Thursday into Friday. The current best guess is that with warm moist air flowing over a warm front to our south, rain will spread into southern Illinois, and as the warm air is forced aloft and condenses, precipitation will change over to sleet and then and accumulating snow in the Chicago area later Thursday afternoon into the evening hours. An extended period of light snow could then follow through Friday, until the low pressure system finally moves east.
Yet another storm?
And the low pressure-triggering impulses keep coming. While still sorting out details on the late workweek storm, preliminary model outlooks have another low pressure system moving out of the southern plains headed our way early the following week – stay tuned!