Drivers are advised to use caution while making their way to work Friday morning as a powerful winter storm that could bring up to 12 inches of total snowfall continues to push through the Chicago area over the weekend.

On Thursday, the National Weather Service issued a winter storm warning for portions of northern Illinois and northwest Indiana that remains in effect until 6 p.m. Friday.

As of noon, O’Hare International Airport had seen 7.3 inches of snowfall, while Midway International Airport had seen 6.8 inches, the weather service said. Heavy to moderate snowfall was expected to continue in the region and could drop up to another inch per hour until about 5 or 6 p.m. Up to two more inches were expected between overnight from Friday to Saturday morning.

The snowfall already affected travel Friday morning, with conditions expected to remain difficult throughout the day, the weather service said.

A narrow band of moderate to sometimes heavy snow will gradually diminish through early evening. Difficult travel conditions will continue at times into this evening, so allow for extra time to reach your destination if travel is necessary. pic.twitter.com/JriKuUY2SR — NWS Chicago (@NWSChicago) February 9, 2018

“If you must travel, keep an extra flashlight, food and water in your vehicle in case of an emergency,” the weather service said. Drivers should be prepared for “significant” reductions in visibility.

The City of Chicago has deployed its full fleet of 280 snowplows and salt spreaders and will focus on clearing Lake Shore Drive and arterial streets before plowing residential streets, according to a statement from Mayor Rahm Emanuel’s office.

“Our city is tackling the first major snow storm we have seen in several years – and it’s clear that Chicagoans are rising to the challenge,” Emanuel said in the statement. “I ask everyone to keep exercising good judgment and remain indoors if at all possible, to take the warnings and advisories seriously, and to check on the well-being of family, friends and neighbors.”

The Cook County Department of Transportation also planned to deploy its full fleet of snowplows and salt trucks in preparation for the start of the storm, the county said in a statement.

GalleryCounty officials and the Illinois Department of Transportation are advising against non-essential driving and urging drivers to yield to snowplows and leave a safe distance between their vehicles and plows.

IDOT announced Friday that the Kennedy Expressway’s express lanes would remain in the inbound direction until Friday night because of the snowfall. The express lanes will close at 9 p.m. for snow removal and will reopen in the inbound direction at 5 a.m. Saturday, when the normal schedule for the reversible lanes will resume.

In addition, more than a thousand flights were canceled at the city’s airports, and transportation agencies were warning commuters of the storm’s impact.

As of 3:50 p.m. Friday, 999 flights had been canceled at O’Hare and 316 flights had been canceled at Midway, according to the Chicago Department of Aviation. Delays at O’Hare were averaging 59 minutes, while delays at Midway were averaging less than 15 minutes.

Metra announced the BNSF railway will use an alternative snow schedule on Friday. The schedule will reduce the number of trains by 10 on the line from Aurora to Chicago to minimize service interruptions.

Metra also announced that it is dispatching 350 workers overnight Thursday into Friday to shovel and salt platforms on all lines, but added that due to the amount of snow that will fall, platforms may become buried again quickly.

The Cook County Department of Homeland Security and Emergency Management is encouraging motorists to take extra precautions when driving during the storm. The department recommends that drivers keep emergency kits in their vehicles, keep their gas tanks at least half full and tell someone where they’re going and which route they’ll take.

Some jurors at the Dirksen Federal Courthouse were told not to worry about coming to court Friday because of the weather.

Chicago Public Schools announced shortly after 4 p.m. Thursday that classes will be canceled on Friday for all students. School buildings will remain open if a student arrives, but the district strongly suggests that students stay home. Classes are expected to resume at their regular times on Monday.

The Chicago Public Library and all Chicago Park District facilities will be open during normal operating hours Friday, the district said. Families looking for ideas of where to send their students for the day were encouraged to call or consult the library and park district’s websites for alternative youth programs and services.

Due to the extreme weather forecast, classes for all CPS students will be canceled on Friday, February 9. — ChicagoPublicSchools (@ChiPubSchools) February 8, 2018

Hundreds of schools in Chicago and the suburbs will be closed Friday, as will several public libraries, park districts and day care centers, according to emergencyclosingcenter.com.

Snowfall is likely to continue throughout the weekend, the weather service said. The Chicago area could see up to another half inch of snow near O’Hare overnight from Saturday to Sunday, with an inch or two possible further south.