NJ Weather: Higher snow totals in latest forecast. Winter storm warnings extended to 10 counties.

Forecasts for the winter storm, expected to dump up to 8 inches of heavy snow on New Jersey on Sunday, have increased in the latest update from National Weather Service.

“The forecast has developed colder and snowier,” the weather service said early Sunday, hours before the storm was expected to hit.

Governor Phil Murphy has declared a state of emergency for all 21 counties starting at 8 a.m. Sunday.

Winter storm warnings have been expanded to now cover all or parts of 10 counties – Bergen, Essex, Hunterdon, Mercer, Morris, Passaic, Somerset, Sussex, Union and Warren.

The biggest change in the latest snow forecast map is along the I-95 corridor, which is now included in the 6 to 8 inch forecast area that covers nearly half of the state.

Sussex County could see pockets of 10 inches of snow in its higher elevations, the weather service said.

“The snow will move in late morning to early afternoon (SW to NE) with the heaviest snow expected 4 to 9 p.m., when snowfall rates could exceed 1 inch per hour,” the weather service said in its last briefing before the storm.

The weather service has focused on the uncertain weather forecast for central New Jersey in the days leading up to the storm. A slight shift in track overnight has pushed snowfall projections higher along these areas.

“Confidence is generally moderate (50-60%),” the weather service said. “There is still some uncertainty regarding rainfall and snowfall amounts with the system, as well as how much mixing will occur.”

Winter weather advisories were also extended overnight to now include parts of 11 counties as snowfall prospects in southern New Jersey increased.

With the exception of the Jersey Shore, most of South Jersey could get 1 to 3 inches of snow, with higher amounts of 3 to 4 inches closer to the Delaware River.

The Philadelphia area is expecting 4 to 6 inches of snow, which will likely affect the NFL playoff game between the Eagles and the Los Angeles Rams, set for a 7 p.m. kickoff. 3 p.m.

AccuWeather’s snow forecast has the northern half of New Jersey with 3 to 6 inches of snow except for the northwest corner in its 6 to 12 inch zone.

After the storm settles Sunday night, temperatures will dip and remain dangerously cold to start the week.

Expect “temperatures to drop well below freezing Sunday evening and remain below freezing through at least Friday,” the weather service said.

Winter storm warnings

Hunterdon, Morris, Sussex and Warren counties from 13.00 Sunday to 01.00 Monday – Heavy snow is expected. Total snow accumulations between 5 and 8 inches. Wind gusts up to 35 mph. Roads, and especially bridges and overpasses, are likely to become slippery and dangerous. Travel can be very difficult. Areas of blowing snow can significantly reduce visibility. Snowfall rates to an inch per hour should develop at times this afternoon.

Mercer and Somerset counties from 13.00 Sunday to 01.00 Monday – Heavy snow is expected. Total snow accumulations between 4 and 7 inches. Travel can be very difficult. Areas of blowing snow can significantly reduce visibility. Snowfall rates to an inch per hour should develop at times this afternoon.

Bergen, Passaic and western parts of Essex and Union counties from 13.00 Sunday to 04.00 Monday – Heavy snow is expected. Total snow accumulations between 5 and 7 inches. Roads, and especially bridges and overpasses, are likely to become slippery and dangerous. Travel can be very difficult.

Advice on winter weather

Camden, Gloucester, Salem and northwest Burlington counties from 10.00 Sunday to 01.00 Monday – Some mixed precipitation to snow is expected. Total snow accumulations between 3 and 5 inches. Roads, and especially bridges and overpasses, are likely to become slippery and dangerous. Areas of blowing snow can significantly reduce visibility. Precipitation should start as a mixture of light snow and rain with possibly some sleet before quickly changing to snow. Snowfall rates to an inch per hour should develop at times this afternoon.

Hudson, eastern Essex and eastern Union counties from 13.00 Sunday to 04.00 Monday – Snow is expected. Total snow accumulations between 3 and 5 inches. Locally higher amounts up to 6 inches possible.

Middlesex County from 13.00 Sunday to 01.00 Monday – Snow is expected. Total snow accumulations between 4 and 6 inches. Plan on slippery road conditions. Areas of blowing snow can significantly reduce visibility. Snowfall rates to an inch per hour should develop at times this afternoon.

Monmouth, Ocean and southeastern Burlington counties from 10.00 Sunday to 1.00 Monday – Some mixed precipitation to snow is expected. Total snow accumulations between 2 and 4 inches. Plan on slippery road conditions. Precipitation should start as some light rain or a light rain, snow and sleet mix before changing to all snow. Snowfall rates of up to an inch per hour should develop at times later this afternoon.

Dangerously cold temperatures

The snow from Sunday’s storm is unlikely to melt quickly as temperatures drop quickly and will remain dangerously cold through the week.

Wind chills below zero are expected in parts of the state through Wednesday.

The coldest day could be Tuesday with highs in the teens and overnight lows in the single digits.

“The coldest period will be Monday night into Thursday morning,” the weather service said. “There will be an increased risk of cooling down and frostbite. Infrastructure impacts may include frozen pipes and increased demand for heat energy.”

Thank you for trusting us to deliver the local weather news you can trust. Please consider supporting NJ.com with a voluntary subscription.