A winter weather advisory is in effect until 2 p.m. in Chicago, with meteorologists predicting snow accumulations of one to three inches across portions of north central and northeast Illinois on one of the busiest travel days of the year.

       The National Weather Service predicted that the highest rates of snowfall will be between 5 a.m. and 10 a.m. They expect one to three inches northwest of 1-55 and one to two inches from Pontiac to Valparaiso, including in Chicago.

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       Snowfall will gradually end later in the afternoon, except for brief snow showers in isolated areas, according to David King, a meteorologist with the NWS in Romeoville. He said light snow will fall through the late morning and early afternoon.

       The weather service warned of “slick and hazardous” travel conditions, especially on bridges and untreated roads. They recommend that drivers plan on increased travel times Sunday morning.

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       “Roads are being reported as slushy in areas,” King said. “Some of the secondary roads have some snow on them that can result in some slick travel.”

       King said a weather advisory typically comes with more severe conditions. However, because it’s the first accumulation of more than one inch of snow in the Chicago metro area and there are high rates of travel for the holiday weekend, they felt the advisory was necessary.

       Snowfall started during a particularly crowded time at Chicago’s airports. The Chicago Department of Aviation estimated that more than 1.65 million passengers would arrive at O’Hare and Midway International Airports between Nov. 21 and Nov. 27 for the Thanksgiving holiday weekend.

       Projections showed that Sunday will be the busiest travel day at O’Hare, with more than 226,000 passengers, a 1.5% increase over last year. Airlines also projected that Sunday will be the busiest day at Midway, with more than 59,000 passengers, a 1% increase compared to last year.

       AAA also predicted that more than 2.4 million Illinoisans will take a road trip of 50 miles or more.

       Conditions at 10 a.m. at Midway Airport are 33 degrees with light snow. King said about half an inch of snow was reported at O’Hare at 6 a.m., but local reports are measuring one to two inches.

       rjohnson@chicagotribune.com