Steady snow moves in overnight, hazardous travel possible

 11:30PM UPDATE: Steady to heavy snow has now spread across the entire Stateline. Snowfall coming down at rates from 0.5"/hour to around 1.0"/hour. 3-6" of new snow is still expected across the entire area with locally higher totals near I-88 where the heaviest bands set up. Snow will begin to ease up after 4AM, with falling snow coming to an end between 6-8AM.

10:30PM UPDATE: Heaviest snow is still just West of the Stateline across much of Iowa but will spread Eastward over the next few hours. Heaviest snow may be capable of accumulating around 1" per hour and limiting visibility to under a half mile.

9:30PM UPDATE: Steady snow is already accumulating on roadways in Beloit. Road conditions can be expected to worsen as steadier snow moves in by 11PM-12AM.

9PM RADAR: First snowflakes now pushing across the I-39 corridor, with steady snow entering NW Illinois and heavier bands of snow in Iowa. Steadiest snow arrives after 11PM-12AM, where rates may exceed 1" per hour at times.

The next round of accumulating snow will arrive late Saturday evening, coating the roadways and adding to the winter wonderland that is Northern Illinois. As of 5PM, light snow is spreading into Eastern Iowa, with some heavy bands further West. Snow is already covering roads and limiting visibility in Des Moines with the heaviest bands, which are set to arrive in Northern Illinois before midnight.

Light snow will reach far Western parts of the Stateline around 8-9PM, with some drier air limiting accumulations at first. Snow will continue to get steadier into the night, eventually turning to a moderate or even heavy snow by around 12AM. Snowfall rates may approach or even exceed 1" per hour between 12-4AM. This will be the worst window for travel. South of I-88, rain or wintry mix will try to cut into snow totals, but North of I-88 will likely remain all snow.

Drier air will cut off the back edge of snowfall after 6AM, leading to a drier afternoon. All told, between 3-6" of snow may come down now across the Stateline, with some locally higher totals wherever the heaviest bands camp out.

This axis may only be 20-40 miles wide. Confidence is higher for this to set up near Carroll and Whiteside Counties where a Winter Storm Warning is in place. Elsewhere, a Winter Weather Advisory is in effect. The Winter Storm Warning will run from 9PM Saturday to 6AM Sunday. The Winter Weather Advisories will run through 6AM Sunday as well, with the exception of Whiteside County which remains in effect until 8AM.

All winter weather alerts will wrap up Sunday morning, but slick spots may remain possible into the afternoon with some blowing and drifting. Arctic high pressure then settles in, turning things much colder for Sunday night as temperatures drop near zero!