Second weather 'bomb' in less than a week is about to strike Mid-Atlantic, Northeast U.S.

Just a few days after a powerful storm caused widespread damage across the Mid-Atlantic and Northeast, another potent nor'easter is tracking toward the region. This one won't be quite as strong as the last event, which was so massive that it caused damage as far away as the Bahamas and Puerto Rico, but it will have more cold air to work with, making a foot or more of snow more likely, especially across interior portions of New England.

The storm will exacerbate the coastal flooding that never completely dissipated in the wake of the last intense storm and astronomical high tides that hit beginning on March 1. In coastal Massachusetts, the first nor'easter severely weakened or destroyed shoreline infrastructure in many communities, making the high waves and coastal flooding from this upcoming storm even more of a threat.

In general, as sea levels rise in response to global warming, weather "bombs" like the two storms in the last week will be capable of causing more severe coastal flooding, since their storm surge will ride on top of a higher baseline of water. And anytime that a major storm coincides with astronomical high tides, as the March 1-4 event did, look out for records to fall along with seawalls.

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Coastal storms, including weather systems that undergo the process known as bombogenesis, in which the minimum central air pressure drops by at least 24 millibars in 24 hours, are not unusual at this time of year along the East Coast.

However, it is rare to see two back-to-back intense storms, both of which would qualify as "bomb cyclones" or "weather bombs," occur within a few days of each other.

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The back-to-back nature of these weather systems is largely due to a favorable weather pattern across the North Atlantic, with a blocking area of high pressure over Greenland preventing storms from moving quickly out to sea, and a see-saw pattern of atmospheric pressure, known as the North Atlantic Oscillation, in a phase that favors East Coast storms.

The snowfall forecast for major cities in the Mid-Atlantic and Northeast is an extremely difficult one, given multiple factors that could cut down on totals, or conversely, drastically raise them.

So far, the consensus forecasts call for about 6 to 8 inches to fall in the Philadelphia area, with much more snow to the northwest of the city, and similar amounts in New York City. In some cases, only about 10 miles will separate areas that pick up about 3 to 6 inches from areas that get socked with 8 to 12 inches or more, which is an astoundingly sharp gradient that is pushing computer modeling to its limits to help forecasters anticipate where the line will fall.

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The Hudson Valley of New York, however, could pick up a foot-and-a-half of snow. In Boston, the snow is expected to mix with rain for much of the time, cutting down on totals there.

Weather Twitter on Tuesday morning was a mix of fascinating discussions on the dynamics behind this storm, and fretting about snowfall totals in the areas where a 20 mile change in the storm track would make a huge difference -- including in New York.

This is a developing storm and story. Check back for updates throughout the day.