These 13 N.J. counties are under winter storm warnings. Forecast for highest snowfall totals.

UPDATED FORECAST TUESDAY: Expect 6 to 12 inches of snow across half of state. Latest updates on shifting storm.

With a major snowstorm setting its sights on New Jersey, 13 counties have been placed under winter storm warnings because of heavy snow and dangerous travel conditions expected Tuesday by the National Weather Service.

The storm’s main target areas for the biggest snowfall totals include a wide swath of northern New Jersey and some parts of north-central New Jersey, according to the latest forecast maps, which expanded the areas that could get pounded with 6 to 12 inches of snow, and some in line for as much as 12 to 18 inches.

UPDATE: As of 7:30 p.m. Monday, the National Weather Service revised its snow forecast map and snow predictions in some of its warnings, with no more areas of New Jersey now projected to get 12 to 18 inches of snow. However, some parts of central New Jersey, mainly near the Interstate 95 corridor, are now projected to get higher snow totals than previously predicted. The winter weather advisories in Mercer, Middlesex and western Monmouth have been upgraded to winter storm warnings.

These are the latest weather warnings, watches and advisories as of Monday evening.

Winter storm warnings

• Sussex County: From 11 p.m. Monday to 3 p.m. Tuesday, with total snow accumulations of 5 to 8 inches, along with a tenth of an inch of ice, expected by the National Weather Service. Particularly heavy snowfall will be possible around the time of the morning commute, with snowfall rates of around 1 to 2 inches per hour possible.
• Bergen, Essex and Passaic counties: From 1 a.m. to 6 p.m. Tuesday, with total snow accumulations of 6 to 9 inches expected, along with winds gusting as high as 35 mph.
• Hudson and Union counties: From 4 a.m. to 6 p.m. Tuesday, with total snow accumulations of 4 to 8 inches predicted, along with wind gusts up to 40 mph.
• Morris and Warren counties: From midnight to 3 p.m. Tuesday, with total snow accumulations of 5 to 8 inches expected. The weather service says locally higher amounts are possible over the higher elevations, especially in northern Warren and Morris counties. Snowfall rates over 1 inch per hour are expected at times Tuesday morning, making for a potentially treacherous morning commute along the I-78 and I-80 corridors.
• Hunterdon County: From midnight to 3 p.m. Tuesday, with total snow accumulations of 4 to 7 inches predicted. Locally higher amounts are possible over the highest elevations, particularly in northern Hunterdon County.
• Mercer County: From midnight to 3 p.m. Tuesday, with total snow accumulations of 4 to 7 inches predicted, along with wind gusts up to 40 mph.
• Middlesex County: From midnight to 3 p.m. Tuesday, with total snow accumulations of 4 to 7 inches predicted, along with wind gusts up to 40 mph.
• Somerset County: From midnight to 3 p.m. Tuesday, with total snow accumulations of 4 to 7 inches expected. The higher amounts in this range will focus on the higher elevations north of Interstate 287.
• Western Monmouth County: From midnight to 3 p.m. Tuesday, with total snow accumulations of 4 to 7 inches predicted, along with wind gusts up to 40 mph.

Winter weather advisories

These counties are under a winter weather advisory, which is not as urgent as a winter storm warning but alerts drivers that hazardous road conditions are possible.

• Camden, Ocean, eastern Monmouth and northwestern Burlington counties: From 3 a.m. to 3 p.m. Tuesday, with rain changing over to wet snow early Tuesday morning. Total snow accumulations of 2 to 4 inches are expected, along with winds gusting up to 45 mph.
• Gloucester and Salem counties: From 3 a.m. to 3 p.m. Tuesday, with up to 2 inches of wet snow expected, along with winds gusting as high as 35 mph.

Current weather radar