A fast-moving clipper system is expected to spread a swath of accumulating snow across northern Illinois late Saturday evening through early Sunday, prompting Winter Weather Advisories for counties generally along and north of Interstate 80. Forecasters say the highest totals, in the 3- to 5-inch range, are most likely from the Rockford region through DeKalb, Lee, Ogle, La Salle and Whiteside counties.

Snow is expected to begin after 9 p.m. Saturday, arriving from west to east as a developing area of lift spreads across the region. Temperatures will stay in the 20s for most locations north of I-80, which will allow snow to quickly accumulate on roadways. The National Weather Service warns drivers to expect slippery travel overnight and during the early hours of Sunday morning.

While confidence is high in accumulating snow across the northern half of the region, the exact placement of the heaviest band remains uncertain.

Areas south of the pink dashed line on the forecast map, including Kankakee, Pontiac and portions of Grundy and Iroquois counties, may experience a brief window of mixed precipitation. Warmer temperatures in the lowest levels of the atmosphere could allow freezing rain or sleet to develop, which may lead to patchy slick spots. Snowfall totals in these southern areas will be lower, generally in the 1- to 3-inch range.

Most of the system will exit shortly after sunrise Sunday as a Canadian high-pressure system moves in. However, light lake-effect snow bands may linger near the Lake Michigan shoreline in northeast Illinois and northwest Indiana into Sunday afternoon.

Drivers planning early-morning travel on Sunday should allow extra time and use caution. The latest road conditions can be found at GettingAroundIllinois.com.