Hour-By-Hour Long Island Winter Storm Forecast

UPDATE 2 p.m. Wednesday: Snow Estimates Rising As Heavy Snow Moves In

UPDATE 5:30 a.m. Wednesday: The winter storm warning has been expanded to all of Nassau County. Here are the latest snowfall total estimates:

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Original story:

A nor'easter is expected to begin impacting the region overnight and it's still not at all clear how much snow Long Island will end up with.

"The coastal accumulation forecast will hinge on a change to rain (if it occurs) and how far north that rain snow line gets," Joe Cioffi, a meteorologist for WPIX-TV and FiOS1 News, wrote on his website Tuesday evening. "Areas near the coast are in a very critical zone. A one degree change could mean the difference from a few slushy inches to a major snowfall."

What starts out as snow in the morning could mix with rain during the afternoon and evening hours. Wherever mixed rain and snow occurs, there could be brief periods of sleet mixed in as well, the NWS says.

Northern Nassau is now the only part of the island that will be under a winter storm warning on Wednesday. The rest of the island, except for the South Fork, will be under a winter storm watch. The South Fork isn't being completely left out, though. It gets a wind advisory with winds expected to gust up to 50 mph, especially late Wednesday afternoon.

A coastal flood warning will be in effect for southern Nassau and southwestern Suffolk from 11 a.m. until 4 p.m. Wednesday. Numerous road closures and widespread flooding of low-lying property, including parking lots, parks, lawns and homes/businesses with basements near the waterfront is possible. Coastal flood advisories have been posted for the rest of the island's coastline.

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The temperature is expected to hold steady around 35-37 degrees all day Wednesday. Things are expected to dry up by early Thursday.

Here's the hour-by-hour forecast (and check out more snow total maps below):

• 1 a.m.- 30 percent chance of snow
• 2 a.m.- 57 percent chance of snow
• 3 a.m.- 57 percent chance of snow
• 4 a.m.- 74 percent chance of snow
• 5 a.m.- 74 percent chance of snow
• 6 a.m.- 74 percent chance of snow
• 7 a.m.- 87 percent chance of snow
• 8 a.m.- 87 percent chance of snow
• 9 a.m.- 87 percent chance of snow
• 10 a.m.- 74 percent chance of snow
• 11 a.m.- 100 percent chance of snow
• Noon- 100 percent chance of snow
• 1 p.m.- 100 percent chance of snow/sleet/rain
• 2 p.m.- 100 percent chance of snow/sleet/rain
• 3 p.m.- 100 percent chance of snow/sleet/rain
• 4 p.m.- 100 percent chance of snow/sleet/rain
• 5 p.m.- 100 percent chance of snow/sleet/rain
• 6 p.m.- 100 percent chance of snow/sleet/rain
• 7 p.m.- 70 percent chance of snow/sleet/rain
• 8 p.m.- 70 percent chance of snow/sleet/rain
• 9 p.m.- 70 percent chance of snow/sleet/rain
• 10 p.m.- 63 percent chance of snow
• 11 p.m.- 63 percent chance of snow
• Midnight- 63 percent chance of snow