An unprecedented winter storm for late October not only dropped heavy snow across parts of central and all of northwest New Jersey,  but caused widespread power outages as many deciduous trees still had leaves. President Barack Obama declared Sussex, Warren, Morris, Hunterdon, Somerset and Middlesex major federal disaster areas. Over 800,000 utility customers lost power. Power was not fully restored until November 4th. Governor Chris Christie declared a state of emergency and urged people to stay off the roads. Shelters and warming stations were opened. About 25 major roadways were closed and 60 others had partial closures. Downed trees and power lines caused major disruptions of rail service in the northern half of the state. Morris County was one of the hardest hit counties in the state. Across Hunterdon, Warren, Morris and Sussex Counties snowfall averaged 6 to 12 inches with higher terrain locations around 15 inches. The 19.1 inch snowfall in Barry Lakes (Sussex County) established a new October snowfall record for the state of New Jersey and is higher than any November snowfall record. In the rest of the Raritan Basin and Mercer County, accumulations averaged 3 to 7 inches and in western Monmouth County and southwest New Jersey accumulations averaged around an inch. Just rain fell in southeast New Jersey.

Precipitation started as snow during the morning of the 29th in Sussex and Warren Counties and remained as snow throughout the event. The snow fell at its heaviest during the afternoon and ended late that evening. Across the Passaic and Raritan Basins as well as Mercer County, precipitation initially started as rain during the morning of the 29th, but as the precipitation intensity increased, it changed to snow between 9 a.m. and 11 a.m. EDT in most places. The snow fell heavy at times between 11 a.m. EDT and 5 p.m. EDT. As precipitation became lighter, it mixed with some sleet and rain, especially at lower elevations that evening. Precipitation ended late that evening. In Monmouth County and southwest New Jersey, precipitation type was intensity driven. Precipitation started as rain during the early morning of the 29th. As waves of heavier precipitation passed over the counties, precipitation type changed back and forth between snow, rain and sleet. As the intensity lessened during that evening, precipitation changed back to rain and ended around Midnight EDT on the 30th.
This snowstorm caused more incidences of damage in Public Service Electric and Gas's service area than Irene did. About 570,000 PSE&G customers lost power throughout the state. About 250,000 Jersey Central Power and Light customers lost power. In Morris County, Interstate 287 was closed in six separate locations. Other sections of major roadways closed in the county included Interstate 80, U.S. Routes 46 and 206 and New Jersey State Routes 10, 24, 53 and 124. In Washington and Mendham Townships alone 11 roadways were closed. Two shelters were opened in the county. In Sussex County, roads were blocked in Newton and Sparta. Sections of New Jersey State Routes 23, 94 and U.S. Route 206 were closed. Sections of Interstate 80 in Warren County were closed. In Somerset County, three separate sections of Interstate 287 were closed. Some schools in the western part of the county were closed on Monday the 31st. Suspended commuter rail service along the Morris and Essex Lines had a ripple effect of increasing roadway congestion as commuters had to take their vehicles instead of the trains. Full rail service was resumed on November 2nd.
Representative snowfall included 19.1 inches in Barry Lakes (Sussex County), 17.0 inches in Lake Hopatcong (Morris County), 16.6 inches in Marcella (Morris County), 15.5 inches in Wantage (Sussex County) and Warren Glen (Warren County), 14.5 inches in Randolph Township (Morris County), 12.5 inches in Holland Township (Hunterdon County), 10.8 inches in Blairstown (Warren County), 10.0 inches in Butler (Morris County), 9.0 inches in Stockton (Hunterdon County) and Hackettstown (Warren County), 8.3 inches in Newton (Sussex County), 8.1 inches in Stewartsville (Warren County), 7.0 inches in Hopewell (Mercer County), 6.3 inches in Phillipsburg (Warren County), 5.6 inches in Woodbridge (Middlesex County), 5.0 inches in Flemington (Hunterdon County) and Bridgewater Township (Somerset County), 4.8 inches in Bridgewater (Somerset County), 4.7 inches in Lawrence Township (Mercer County), 4.6 inches in Metuchen (Middlesex County) and Morristown (Morris County), 3.0 inches in New Brunswick (Middlesex County), 2.0 inches in Freehold (Monmouth County), 1.4 inches in Berlin (Camden County), 1.3 inches in Cream Ridge (Monmouth County), 1.2 inches in Florence and Mount Laurel (Burlington County) and 1.0 inch in Cherry Hill (Camden County).
The unprecedented winter storm was caused by an intensifying low pressure system that moved from Georgia on the evening of the 28th northeast to Cape Hatteras, North Carolina at 8 a.m. EDT on the 29th. From there it took a turn more toward the northnortheast and was off the Delmarva Peninsula at 2 p.m. EDT on the 29th. The low pressure system started moving to the northeast again and passed southeast of Montauk Point, New York at 8 p.m. EDT on the 29th and just southeast of Nantucket, Massachusetts at 2 a.m. EDT on the 30th. While the storm track would be ideal for a winter time snow, for an event like this to occur in late October, it needed assistance from a high pressure system that left dry air initially in place and made it easier for a process known as evaporational cooling to take place and make it cold enough for snow. Once the precipitation intensity became heavier, another process known as dynamical cooling (heat is removed from the air mass as it melts the snow) more than compensated for the warm air that was moving in from the Atlantic Ocean to keep precipitation in west central and northwest New Jersey falling as snow.

Heavy Snow in SUSSEX, NEW JERSEY
From 29-OCT-11 10:00:00 to 29-OCT-11 22:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Heavy Snow in WARREN, NEW JERSEY
From 29-OCT-11 09:00:00 to 29-OCT-11 22:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winter Storm in MORRIS, NEW JERSEY
From 29-OCT-11 09:00:00 to 29-OCT-11 23:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winter Storm in SOMERSET, NEW JERSEY
From 29-OCT-11 09:00:00 to 29-OCT-11 22:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winter Storm in MIDDLESEX, NEW JERSEY
From 29-OCT-11 09:30:00 to 29-OCT-11 22:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winter Storm in HUNTERDON, NEW JERSEY
From 29-OCT-11 08:00:00 to 29-OCT-11 22:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winter Storm in MERCER, NEW JERSEY
From 29-OCT-11 08:00:00 to 29-OCT-11 22:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winter Weather in WESTERN MONMOUTH, NEW JERSEY
From 29-OCT-11 10:00:00 to 29-OCT-11 21:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winter Weather in NORTHWESTERN BURLINGTON, NEW JERSEY
From 29-OCT-11 09:00:00 to 29-OCT-11 21:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winter Weather in CAMDEN, NEW JERSEY
From 29-OCT-11 10:00:00 to 29-OCT-11 20:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter