A low pressure system approaching from the northwest will bring the next round of winter weather to the Chicago metro area from late tonight through Monday morning. Looking at this afternoon’s water vapor satellite image, we can see moisture from this approaching system currently pushing into Minnesota and Iowa (image source: College of DuPage).
This will be a fast-moving but potent system with about 6-8 hours of heavy snowfall expected overnight. The heaviest period of snowfall will be from about midnight through sunrise with snowfall rates of 1″/hour or higher expected at times. The next image from the HRRR model shows the projected radar reflectivity at midnight tonight, with widespread snow filling in across the Chicago area (image source: College of DuPage).
Snow that falls will easily accumulate on all surfaces given the cold temperatures in place. However, it should be noted that a significant warming trend will occur overnight as warm air pushes in from the south. Temperatures will rise from the low teens at around midnight tonight into the low 30s by mid-morning Monday.
Toward the back edge of the main area of precipitation Monday morning, we could even see precipitation briefly change to light freezing rain, before a cold front arrives and temperatures quickly drop again. Lingering scattered snow showers will continue through the day Monday, but most of the accumulation will occur overnight.
Total snowfall amounts across the greater Chicago area overnight are likely to range from 4-7″ for most areas, with significant road impacts expected during the Monday morning commute. Heavier precipitation and colder air with higher snow to liquid ratios will exist farther north, so across the northern suburbs to the Wisconsin border, snowfall amounts look to be more in the 5-10″ range.
In addition to snowfall, winds will be gusty from the south at 15-25mph with gusts to 30mph overnight through Monday morning, becoming northwesterly with similar speeds Monday afternoon. As a result, areas of blowing and drifting snow can be expected.
Following this storm, a well advertised blast of arctic air will arrive with record cold temperatures expected for the middle part of the week, including dangerous wind chills.