It’s official in Suffolk -- the storm stalled over the county is a blizzard, which has been unloading 2 to 4 inches of snow per hour since 1 a.m., the National Weather Service said.

As of 3 a.m., 14.7 inches of snow was reported at Long Island MacArthur Airport in Ronkonkoma and 12.1 inches at the weather service office in Upton; as of 1 a.m., 5.3 inches was recorded by a trained spotter in Seaford, the weather service said.

“There’s an absolutely heavy band of snow settling over Suffolk,” said meteorologist Brian Ciemnecki in Upton. “It’s just dumping snow.”

Although up to 30 inches is still forecast for Suffolk, the forecast was downgraded to between 18 and 24 inches for Nassau.

The blizzard warning remains in effect until midnight Tuesday in Nassau and Suffolk.

Winds have been blowing at up to 40 mph in much of Suffolk and higher on the East End, creating whiteout conditions that have cut visibility to less than a quarter-mile, meteorologists said. But expected wind gusts were downgraded from hurricane force of 70 mph to 50 mph tops, the forecast said.

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County and town officials worried that whiteout conditions would force a halt to snow removal, but that has not happened yet on a massive scale.

Brookhaven Town Highway Superintendent Dan Losquadro said the big problem caused by high winds was snowdrifts blown against fences. That required payloaders to lift the snow and take away, bucket by bucket, which took more time than plowing, he said: “Some of these drifts are already five feet high.”

The brunt of the storm is expected to end by midmorning, but snow will continue to fall during the daytime, the service said.

Storm bands heavy with snow have been forming off the southeast coast of Long Island and moving northwest, hanging over the Island until at least breakfast time, said meteorologist David Stark at the weather service’s Upton office.

“Mature storms like this tend to slow down as they get to their peak intensity,” he said.

Long Island is expected to take the brunt in the state of what is being called a “life-threatening” blizzard that may unload 30-plus inches of snow or more in certain parts, especially the East End.

The storm’s 2 to 4 inches of snow an hour is “a ridiculous snowfall rate,” weather service meteorologist Adrienne Leptich said.

“I wouldn’t be surprised if there’s even more than that,” she said.

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In some cases, storm problems did not materialize as some had feared.

PSEG Long Island has been reporting scattered outages, but not the high numbers some had anticipated.

Accidents and 911 calls were light or barely above a normal day, Suffolk and Nassau police said.

As ordered by Gov. Andrew M. Cuomo, all roads from Ulster County south to Long Island were shut down at 11 p.m. to help snowplows clear the roads faster and to keep motorists from being stranded. It was one lesson learned from the 2013 storm that stranded hundreds of motorists on the Long Island Expressway in Suffolk.

Trucks were dispatched to block the LIE ramps as soon as the curfew arrived.

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By 11 p.m., as Nassau County Executive Edward Mangano traveled the roads, the streets were looking like a ghost town, he said.

“The roads are well plowed,” Mangano said. “The roads are passable. We thank our residents for heeding the warning because clearly the roads were ... noticeably empty.”

By 11 p.m., authorities had responded to about 150 accidents, with half of them needing ambulances, but they were not life-threatening injuries, he said. Residents had also heeded the call not to clog 911 lines but to call the county’s nonemergency hotline, he said.

Suffolk County Executive Steve Bellone did not return calls.

State parks and town officials said they would look out for beach erosion but would not be able to gauge any damage until the storm ended.

Meteorologists said there appeared to be a pre-midnight lull to the precipitation after a 60-mile-wide snow band hovered over the Long Island Expressway in the early afternoon, then disbanded in the early evening. The band dumped on motorists who took the advice of officials to head home earlier than usual, causing an early rush hour and traffic jams.

Some towns on Long Island ordered motorists off the streets earlier. The deadline was 7 p.m. in Brookhaven, where a populace irate over unplowed, impassable roads in 2013 helped force the resignation of the acting highway superintendent.

With so much precipitation forecast, one state contractor said the challenge isn’t visibility or slick roads, but the rapid “excavation” of all the snow from parking lots and roadways into unused areas, such as the Jones Beach parking areas.

It’s a chore with the number of drivers and trucks available, said Billy Haugland Jr., a principal of Grace Industries, a Plainview-based highway construction company hired to move snow off Sunrise Highway, the Meadowbrook State Parkway and more.

But state officials and the Long Island Contractors Association, whose members are being hired for the snow-clearing jobs have been trying to get ahead of the storm with early planning and putting workers on standby, Haugland said.

He saw it as a marked difference from the 2013 torrent of snow: “The storm dumped so much snow that it was completely ‘chase our tails.’ ”

In a race against the brunt of the storm, drivers for Intercounty Paving in Hicksville were to have begun delivering 800 tons of salt — about 40 truckloads — from one of the state’s depots in Merrick to places along the South Shore and eastern Suffolk.

Frank Lizza, general manager of the Hicksville company, said motorists appeared to have heeded warnings by 7:30 p.m.: “The drivers say most of the people have packed it in for the evening, making their jobs much easier.”

His trucks also have been contracted to block the ramps to the LIE at 11 p.m. to prevent motorists from getting on.

“This is going to be a dangerous situation,” Cuomo said from a state Department of Transportation yard in Melville.

He told Long Islanders not to “trifle” with the weather warnings, later saying anyone out beyond 11 p.m. is being “irresponsible.”

“This is not a time to be casual,” the governor said.

Earlier Monday, Suffolk County Executive Steve Bellone also urged residents to head home before the blizzard hit.

“And if you are home, stay home throughout the duration of the storm,” Bellone said Monday at a news conference.

County residents “need to be prepared to shelter in place,” because the massive snow removal operation “may take days,” Bellone said.

Nassau County Executive Edward Mangano said Nassau has pre-treated its county roads with a brine solution and has salted some other areas.

Thunder and lightning are possible, forecasters said. “There is the potential with this storm of some instability, especially in some of these very intense bands,” meteorologist Ciemnecki said. “You can get some thunder with the snow. When you see heavy snowfall, of 2, 3, 4, 5 inches in an hour, the instability in the atmosphere is enough to cause lightning and rumblings of thunder.”

Thundersnow had not been seen yet, the weather service said.

By 5 a.m., the weather service had canceled both the coastal flood advisory and the coastal flood warning for everywhere but eastern Long Island, saying in a coastal flood statement that "minor coastal flooding occurred with the overnight high tide. ... No additional coastal flood is expect with this storm."

A coastal flood warning remains in effect along the coasts of eastern Long Island, including the bays between the twin forks, where tidal departures between 2.5 and 3 feet above the astronomical tide are possible through 7 a.m. Tuesday.

The snowfall record to beat is the 27.8 inches that fell Feb. 8 and 9, 2013, at MacArthur Airport in Ronkonkoma, where weather records have been kept since 1984 by the weather service.

That storm brought snowfall rates of up to 6 inches an hour and accompanying thunder, lightning and small hail, according to the National Climatic Data Center’s storm database.

Temperatures will remain in the mid- to low 20s through Tuesday afternoon. Lows could fall into the teens by Tuesday night as the storm tapers off. The storm should be completely cleared by Wednesday morning.

Another slight chance of snow returns Thursday night. Temperatures should linger in the 20s and 30s heading into the weekend.

With Patricia Kitchen, Gary Dymski, David M. Schwartz, Laura Figueroa and John Asbury