Nor’easter forecast: A bomb cyclone with hurricane power will unleash snow this

“The models continue to show a nor’easter with blockbuster potential for the weekend, mainly late Friday through Saturday,” CNN meteorologist Brandon Miller says.

There are still questions about how much snow will pile up and how extreme winds will get.

“Heavy snow is most likely in parts of New England,” the Weather Prediction Center said Wednesday morning. “Heavy snow is still possible farther south along the East Coast, including the major I-95 metropolitan areas from New York City to Washington DC, but that is more uncertain at this time.”
The storm is expected to form in the Atlantic Ocean just off the coast of Georgia, then rapidly strengthen — a process known as bombogenesis — overnight Friday and track Saturday up the East Coast.
“Guidance indicates potential for this storm to undergo bombogenesis, meaning its central pressure drops at least 24 mb in 24 hours,” the Boston weather service office said, referring to the unit of pressure known as millibars. “This creates a very tight pressure gradient, meaning strong, potentially damaging winds will accompany the snow.”

“This storm is likely to strengthen at a rate, and to an intensity, equivalent to only the most powerful hurricanes, so the high-end potential of this storm cannot be overstated. But with nor’easters, like in real estate, it will all come down to location, location, location,” Miller said.

Uncertainty in the forecast is pretty common more than 48 hours before a storm even has formed, as the Boston National Weather Service office noted Wednesday on Twitter.

“Well, the average model error at this time range (3 days out) is over 150 miles! For example, where will the rain/#snow line setup? 150 miles could range from Cape Cod, MA to New Haven, CT. Hence, still too early.”

Both forecast models predict this strengthening, but their storm tracks up the East Coast are different, changing what people could expect from Washington, DC, to Boston.

“For those that have been following along, I know you’ve heard it repeated to death, but the key message continues to be the same: guidance is trending favorably for a big storm, but the exact track remains uncertain,” the Boston office said. “This track is what will tell us exactly where the greatest snow, wind, and coastal flooding concerns are.”

A “farther offshore track of the low will decrease snow amounts while a track closer to shore will increase snow amounts and if the low gets close enough to the coast, a wintry mix will be possible for some eastern coastal sections (This is looking less and less likely),” said the New York office of the National Weather Service.

Blizzard conditions, coastal flooding are on the table

While it’s too early to pinpoint exact totals, it looks like the storm will hit all metro areas along Interstate 95 from Virginia to Maine starting Friday and through the day Saturday. Philadelphia, New York and Boston could get a foot of snow — or much more.

Winds of 50 mph or more are likely throughout the Northeast, with even higher gusts possible, especially along the eastern coastlines. These strong winds combined with snow will create blizzard conditions.

“A closer track would also mean higher winds and potential for blizzard conditions near the coast,” the weather service office in Philadelphia said.

A blizzard happens when snow combines with winds gusting over 35 mph for more than three hours and creates visibility of less than a quarter of a mile.

“Significant coastal impacts are possible in the Northeast, including coastal flooding and beach erosion,” the prediction center said.

The stronger the storm, the greater the surge of water along the coast will be. Timing also matters a lot.

The Colorado Hooker, Pineapple Express and other colorful winter storm names

“Coastal flooding is a concern thanks to astronomically high tides on Saturday,” the Boston weather service office said. “The combination of strong northeast winds and high seas will bring storm surges that, if coinciding with high tide, would lead to minor or moderate coastal flooding.”

The difference in storm timing — even as few as six hours — would make a massive difference in impact on coastal flooding and erosion concerns.

One thing is sure: Meteorologists will be glued to computer forecast model runs all day Wednesday.

“Today’s trends will certainly be important,” the weather office in Philadelphia said. “Sampling will be steadily improving, and ‘big picture’ model solutions should start converging in the next 12 to 24 hours.”

In layman’s terms: We will know more details Thursday.

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