The scope of New Jersey’s first significant snowstorm of the season is expanding, as snow, sleet and rain continues to fall around the Garden State Sunday evening.

Schools in several counties have already announced closings for Monday.

The National Weather Service reported in its 5 p.m. update that a wide zone including areas around Trenton to Camden could get more snow by Monday night than originally forecast - up to 3 to 5 inches of accumulation.

Hunterdon, Somerset and Mercer counties are now under a winter storm warning, joining Sussex, Warren, Passaic, Morris and western Bergen counties. The warnings have also been extended to 4 a.m. Tuesday, and 7 a.m. in Bergen.

And a coastal flood advisory has been issued for the northern and central coast, the weather service said, with “spotty minor flooding” possible along the southern coast coast.

The heaviest snow totals remain in Sussex County, where up to 8 inches is in the forecast.

The weather service warned that ice will continue to develop on elevated surfaces, bridges, overpasses, trees and wires sooner than it will on roads and walkways, in the northwest part of New Jersey.

Earlier Sunday, speeds were reduced on the New Jersey Turnpike and Garden State Parkway.

The wintry mix was causing delays of over two hours at Newark Liberty International Airport, as well as other major airports in Philadelphia and New York.

Later Sunday evening, the state Department of Transportation banned commercial vehicles from parts of interstates 80, 287 and 78.

Rob Jennings may be reached at rjennings@njadvancemedia.com. Follow him on Twitter@RobJenningsNJ. Find NJ.com on Facebook.

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