A winter storm produced a protracted mix of snow, sleet and freezing rain across most of the northern half of New Jersey with less of an impact across southwest and coastal central New Jersey. Snow and sleet accumulations in most of the northern half of New Jersey averaged 1 to 3 inches and ice accretions averaged two tenths to five tenths of an inch. Across southwest and coastal central New Jersey snow and sleet accumulations were around an inch or less and ice accretions averaged around one tenth of an inch. Mainly rain fell across southeast New Jersey.
Precipitation started as snow throughout most of New Jersey during the evening of the 17th. As warmer air moved in aloft, the snow changed to sleet and freezing rain in southwest New Jersey around Midnight EST on the 18th and between Midnight EST  and 6 a.m. EST on the 18th in the northern half of the state. Any snow or freezing rain changed to plain rain fairly quickly across southeast New Jersey. The erosion of cold air near the surface took longer and the transition to plain rain occurred in southwestern New Jersey area between 5 a.m. and 8 a.m. EST on the 18th and across the Raritan Basin late that morning. In Northwest New Jersey, the change to plain did not occur in some places until the middle of the afternoon on the 18th just as the precipitation was ending.
Untreated roadways were very hazardous and the prolonged period of sleet and freezing rain impacted commuting on the 18th especially from the Raritan Basin northward. Speed restrictions were posted along parts of the New Jersey Turnpike. New Jersey Transit cross-honored bus and rail passes as there were delays in northern New Jersey of  up to twenty minutes. Some of the worst reported accidents included an overturned vehicle on Westbound Interstate 195 near the New Jersey State Route 35/Route 34 turnoff, in Wall Township (Monmouth County) that closed the right lane and shoulder, a vehicle spin-out on Southbound Interstate 287 near the intersection with Interstate 80 in Morris County that blocked the left lane and an overturned vehicle that closed U.S. Route 206 in Frankford near Newton Ave in Sussex County.  In Sussex County, in Sparta Township, a 30-year-old woman was critically injured after her vehicle slid into oncoming traffic on White Lake Road. The 52-year-old male driver in the other vehicle was also injured. In another township accident, a 51-year-old male, 50-year-old female and their 15-year-old son were injured when they were rear ended at the intersection of State Route 15 and White Lake Road. The ice took down wires and caused outages on Lakeview Road and Tomahawk Trail. In all, Sparta Township fielded 72 calls for assistance during the winter storm.
Representative snow and sleet totals included 2.5 inches in Green Pond (Morris County), 2.1 inches in Hardyston (Sussex County) and Liberty (Warren County), 2.0 inches in Whitehouse (Hunterdon County), Randolph (Morris County) and Hopewell (Mercer County), 1.5 inches in Somerville (Somerset County), 1.2 inches in New Brunswick (Middlesex County) and 0.9 inches in Mount Holly (Burlington County). Ice accretions reached 0.6 inches in Hardyston (Sussex County), 0.4 inches in Phillipsburg (Warren County) and 0.25 inches in Hopewell (Mercer County) and Edison (Middlesex County). The combination of the onshore flow and higher than normal astronomical tides associated with the full moon caused isolated minor tidal flooding along the New Jersey coast during the morning high tide on the 18th. The high tide at Cape May (Cape May County) reached 6.74 feet above mean lower low water. Minor tidal flooding starts at 6.7 feet above mean lower low water.
The wintry mix of precipitation was caused by the combination of a low pressure system that emerged from the Gulf of Mexico and an arctic high pressure system that left cold air in place, especially near the surface. The low pressure system moved from the eastern Gulf of Mexico on the 17th northeast to near Cape Hatteras, North Carolina at 7 a.m. EST on the 18th. It moved northnortheast and was just east of Atlantic City, New Jersey at 1 p.m. EST on the 18th. From there it turned more to the northeast and passed south of Montauk Point, New York by 7 p.m. EST that evening. The surface high pressure system was over New England on the evening of the 17th and at 7 a.m. EST on the 18th was centered over Nova Scotia. As it moved farther to the east, the combination of that motion and the low pressure system moving up the east coast cut off the supply of sub freezing temperatures near the coast.

Winter Weather in SALEM, NEW JERSEY
From 17-JAN-11 20:00:00 to 18-JAN-11 04:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winter Weather in CUMBERLAND, NEW JERSEY
From 17-JAN-11 20:00:00 to 18-JAN-11 01:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winter Weather in GLOUCESTER, NEW JERSEY
From 17-JAN-11 20:00:00 to 18-JAN-11 04:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winter Weather in CAMDEN, NEW JERSEY
From 17-JAN-11 20:00:00 to 18-JAN-11 06:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winter Weather in SOUTHEASTERN BURLINGTON, NEW JERSEY
From 17-JAN-11 20:00:00 to 18-JAN-11 04:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winter Weather in NORTHWESTERN BURLINGTON, NEW JERSEY
From 17-JAN-11 20:00:00 to 18-JAN-11 07:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winter Weather in WESTERN OCEAN, NEW JERSEY
From 17-JAN-11 21:00:00 to 18-JAN-11 04:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winter Weather in EASTERN MONMOUTH, NEW JERSEY
From 17-JAN-11 22:00:00 to 18-JAN-11 02:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winter Weather in WESTERN MONMOUTH, NEW JERSEY
From 17-JAN-11 22:00:00 to 18-JAN-11 07:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winter Storm in MERCER, NEW JERSEY
From 17-JAN-11 21:00:00 to 18-JAN-11 07:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winter Storm in MIDDLESEX, NEW JERSEY
From 17-JAN-11 22:00:00 to 18-JAN-11 08:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winter Storm in SOMERSET, NEW JERSEY
From 17-JAN-11 22:00:00 to 18-JAN-11 11:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winter Storm in HUNTERDON, NEW JERSEY
From 17-JAN-11 22:00:00 to 18-JAN-11 11:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winter Storm in MORRIS, NEW JERSEY
From 17-JAN-11 23:00:00 to 18-JAN-11 11:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winter Storm in WARREN, NEW JERSEY
From 17-JAN-11 23:00:00 to 18-JAN-11 12:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winter Storm in SUSSEX, NEW JERSEY
From 17-JAN-11 23:00:00 to 18-JAN-11 15:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter