• Afternoon snow totals are expected to be 3 to 7 inches in Queens, the National Weather Service said this afternoon, with 4 to 8 more inches falling tonight, meaning the new depth forecast is 7 to 15 inches.
• Mayor de Blasio was scheduled to hold a briefing on the storm at 6:30 p.m.
• All branches of the Queens Library will close at 5 p.m., library spokeswoman Joanne King announced at 2:12 p.m.
• Many city buses are running with chains on their rear wheels.
• A Campaign Finance Board hearing on the last election that was set for Jan. 22 has been postponed.
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As you may have noticed, the snow has begun. It came in about two hours ahead of schedule, around 8 a.m. in Queens, even though at least some broadcasters were still predicting as late as 7 a.m. that it would not start until around 10.
The National Weather Service also increased its snowfall predictions overnight, with the city now expected to get 8 to 12 inches. The depth forecast has repeatedly been increased over the last day or so, from 3 to 6 inches, then to 4 to 8 and now 8 to 12.
That forecast applies to the entire city. The storm is expected to be worse further east: In eastern Nassau and Suffolk counties, the forecast was for 10 to 14 inches.
A Winter Storm Warning issued by the NWS was to be in effect from noon Tuesday to 6 a.m. Wednesday, but the snow beat it by four hours.
Along with heavy snowfall, the NWS warns of temperatures of 12 to 22 degrees, with a wind chill factor making it feel like 10 below zero late Tuesday night. Winds are expected to range from 15 to 25 miles an hour with gusts to 35. Visibility will fall to a quarter-mile or less at times.
"Snowfall will begin late Tuesday morning and will continue through Tuesday night ... tapering off early Wednesday morning," the warning said. "The heaviest snowfall will occur Tuesday afternoon and evening."
An updated warning issued a little before 5 a.m. Tuesday also said, "Impacts... Falling... Blowing... And drifting snow will cause hazardous travel and walking conditions across the area... Impacting the late afternoon and evening commute. Snow removal will be difficult this afternoon through tonight. Prolonged exposure to frigid cold and low wind chills could cause frost bite. Dress appropriately."
The storm is a clipper system from the west that forecasters had said will turn into a nor'easter. It has been dubbed Janus.
— Peter C. Mastrosimone
This article was updated around 9:30 a.m. Tuesday to reflect the fact that it is snowing, and to include the latest snow depth predictions from the National Weather Service. Later updates are at the top of the story.