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UPDATED 6:40 p.m. ET: The latest forecasts based on updated computer model runs are clearly pointing in the direction of much higher snowfall totals than previously expected from coastal New Jersey all the way northeast to Maine.

In New York, the revised forecast of snowfall rates approaching 4 inches per hour, winds sustained at tropical storm force and gusting near hurricane force (74 miles per hour) that will cause near-whiteout conditions at times and snowfall totals that could be as high as 3 feet led New York Mayor Bill DeBlasio to strike a disquieting tone at an afternoon press conference, warning residents that this storm could be one of the worst the city has ever faced. As an indication of how severe this storm is likely to be, blizzard warnings have been issued from Atlantic City, N.J. to Eastport, Maine, a distance of 540 miles. The entire states of Connecticut and Rhode Island are under blizzard warnings, as is all of the New York City metro area, as well as Hartford, Providence, Boston and Portland, Maine.

National Weather Service meteorologists from New Jersey to Maine have been coordinating their forecasts and warnings while pouring over the latest data. Computer model data and other information available on Sunday afternoon back up the DeBlasio's statements and, if anything, suggest he may have slightly undersold the risks the storm poses to the city of 8.4 million. The high-end snowfall forecast for New York, as of Sunday at 7 p.m. ET, was 36 inches. To put that into perspective, New York's all-time largest snowfall was 26.9 inches in 2006.

According to Gary Szatkowski, a meteorologist for the Weather Service's Philadelphia office, the storm forecast has evolved rapidly in the past 30 hours, since just over a day ago this storm was not on most meteorologists' radar screens at all. With the most recent information, Szatkowski told Mashable in an interview, “Our forecast confidence is increased in the sense that we’ve moved our forecast toward the higher end of the scale.” He said that if the forecast were to be inaccurate in one direction or another, it's more likely the forecast would be too high, with observed snowfall amounts lower than forecast.

A potentially crippling and historic blizzard is forecast to bury areas from New York City northward to southern New England under a wind-swept blanket of 2 feet or more of snow between Monday night and Wednesday morning, as a storm rapidly strengthens just off the East Coast.

As of Sunday at 11 a.m. ET, blizzard watches were in effect from central New Jersey to the North Shore of Boston, a heavily populated urban corridor.

See also: Why the world seems quieter when it snows

The storm may prompt the virtual shutdown of large portions of New Jersey, southeastern New York, Massachusetts, Connecticut and Rhode Island between Monday night and Tuesday night, as it whips up winds gusting to 70 miles per hour or more, along with snowfall rates approaching 4 inches per hour at times.

Forecast projection for sea level air pressure, winds and six-hour accumulated precipitation on Tuesday morning. Image: WeatherBell Analytics

In anticipation of the storm, the National Weather Service has issued blizzard watches, coastal flood watches and a host of other watches and warnings from New Jersey to Maine, as computer models used to help forecast high-impact weather events are unanimously pointing to a major — if not history-making — storm.

Here's regional view of 'reasonable worst case scenario' guidance from @NWSWPC This is for main storm, not clipper. pic.twitter.com/UJfZen2Sxm — Gary Szatkowski (@GarySzatkowski) January 25, 2015

The timing of the worst weather looks to be between late Monday into Tuesday for New York City, where forecast uncertainty is a bit higher than for southern New England, since New York could be on the western edge of the heaviest snowfall. Blizzard watches are in effect for northern New Jersey and New York City from late Monday into Tuesday night, with snowfall totals possibly reaching as high as 2 feet even in the city itself. A wobble in the storm track of just 25 to 50 miles east or west will mean the difference between half a foot of snow and a foot and a half in the Big Apple.

A blizzard watch means there is a potential for blizzard conditions, whereas a blizzard warning would indicate a high likelihood of imminent blizzard conditions. Warnings may be issued as soon as Sunday night, depending on additional weather data. Two of the main reasons for such an expansive area of blizzard watches are the high winds expected with the storm, and the light, fluffy nature of the snow that will fall, making it prone to blowing and drifting.

If you need a refresher on what qualifies as a #Blizzard, here you go pic.twitter.com/WixCHfOg81 — Greg Diamond (@gdimeweather) January 25, 2015

Mean snowfall forecast from the European computer model, showing a swath of heavy snow from Philadelphia to Maine early this week. Image: WeatherBell Analytics

The storm will reach a peak in southern New England on Tuesday into Tuesday night, with blizzard conditions likely from Long Island to coastal Maine, where snowfall totals in excess of 2 feet are likely.

There are many uncertainties involved in pinpointing the areas of heaviest snow this far in advance, as intense storms like this often spawn small-scale bands of very heavy snow, known as "mesoscale bands," but the agreement among computer models that this will be a major event all but assures a high-impact storm not seen in the Northeast since 2013 — and maybe well before that.

Here's the headline from a forecast discussion published by the National Weather Service's forecast office in Boston on Sunday morning:

A MAJOR AND POTENTIALLY HISTORIC WINTER STORM WILL AFFECT THE REGION MONDAY NIGHT INTO TUESDAY NIGHT...TRAVEL MAY BECOME IMPOSSIBLE AND LIFE THREATENING...

The NWS is calling this "a textbook case for a major winter storm/blizzard in southern New England."

In addition to the snow and near hurricane force winds, significant coastal flooding due to high waves and the winds blowing water onshore could occur along east-facing shorelines, the NWS is warning. This could erode beaches and threaten oceanfront property from about Cape May, New Jersey, to coastal Maine.

Play it safe by preparing ahead for winter storms and blizzards. Pay close attention to weather forecasts & warnings. pic.twitter.com/oxOkNeEjnI — James P. O'Neill (@NYPDChiefofDept) January 23, 2015

Over time, sea level rise related to global warming is making storms such as this one more damaging, by giving storm tides a higher baseline from which to launch off of — much like a basketball player that can make more slam dunks as the floor of the court is slowly raised.

Travel by any means is going to be difficult or impossible in much of the Northeast from Monday night to Tuesday night, with widespread flight cancelations and airport closures likely in cities, such as New York, Hartford, Providence, Boston, and Portland, Maine.

Here's what the National Weather Service office in New York City is saying about travel conditions there during the storm:

EXTREMELY DANGEROUS TRAVEL DUE TO HEAVY SNOWFALL AND STRONG WINDS...WITH WHITEOUT CONDITIONS LIKELY. SECONDARY AND TERTIARY ROADS MAY BECOME IMPASSABLE. STRONG WINDS MAY DOWN POWER LINES AND TREE LIMBS.

The storm responsible for the blizzard conditions is currently zipping rather gingerly across central Illinois, bringing generally light snow with it. However, on Monday, it will reach the Atlantic Coast, where a combination of several shots of potent energy from the jet stream and additional fuel provided by the Gulf Stream will help shape-shift this once placid weather system into a rapidly strengthening beast of a storm, often referred to by meteorologists as a weather "bomb" because of its rapid intensification rate.

Indeed! MT @snodgrss: Outstanding upper lvl support for Nor'easter. Amplified trough + coupled jet streaks = deep low pic.twitter.com/jsBQplu1H5 — Jim Cantore (@JimCantore) January 25, 2015

One of the most uncertain aspects of the forecast concerns locations on the western periphery of the heavy snow shield.

This would include places like the Hudson Valley of New York, New York City and much of central and northern New Jersey. Snowfall totals in these areas could range from a relatively modest 6 inches — if the storm drifts just a bit further east than currently forecast — or closer to 2 feet, as currently forecast for a track that hugs the coastline.

This storm could prove to be a major test for New York City Mayor Bill DeBlasio, who was criticized last winter for the poor snowfall removal performance of city plows during a more modest storm. Also to be tested is Boston's new mayor, Martin J. Walsh, who was sworn in on Jan. 6, 2014, and has not been at the helm of the city during such a high-impact storm. Mayoral elections have previously been won or lost based mainly on snow-removal performance.

The big northeastern cities have yet to see a major snowstorm so far this winter, which could heighten the impacts of a powerful storm like this — much like a heat wave that hits in May rather than in August, when people are more accustomed to hot temperatures. A weaker storm did bring several inches of snow over the weekend, but mainly to inland areas of southern New England.

Following the blizzard, a dangerously cold Arctic outbreak waits in the wings, with wind chills forecast to plunge to as low as minus-30 degrees Fahrenheit in New Jersey during the first week of February.