Not-quite-a-bomb-cyclone spoils winter weather
A rapidly intensifying low pressure system off the coast is keeping the worst of the snow away from Boston, New York City and Washington, DC.
A cargo plane takes off from the runway after a winter snow storm affected the area at O’Hare International Airport in Chicago, Illinois on November 30, 2025.
Jim Vondruska/Getty Images
A winter storm that probably won’t reach “bomb cyclone” status is still bringing nasty weather to the eastern half of the US today, with the potential to dump up to a foot of snow in parts of New York state and southern Maine.
Meteorologist and CEO Alan Gerard says this first significant burst of winter weather for the region is due to a low pressure system that has been moving eastward from the Midwest through the Ohio Valley and Mid-South over the past few days. balanced weatherDue to this disturbance, a second low pressure area is developing on the mid-Atlantic coast, National Oceanic and Atmospheric Administration (NOAA) Weather Prediction Center meteorologist Ashton Robinson Cook says this other low is expected to intensify as it moves north toward Cape Cod during today, but will likely remain “a bit away from the bomb cyclone area,”
Bomb cyclones occur when a rapid drop in pressure occurs within 24 hours of a storm forming in the mid-latitudes. The exact pressure drop depends on latitude: for example, at 40 degrees latitude (approximately New York City), the pressure should drop about 18 millibars in 24 hours, according to NOAA. Cook says the cyclone moving north from the East Coast will still be impressively intense, and will bring high winds to parts of Maine along with snow.
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But this low pressure keeps warm air from the most populous parts of the Northeast to the Mid-Atlantic, Gerard says. “That’s why we’re getting a lot of rain or a little mixed rain from Boston through DC,” he says. The heaviest snowfall, about eight to 12 inches, is expected in southern New England and New York state.
Cook says most of the precipitation will clear by Wednesday morning, although cold front winds will continue across the central and eastern US through next weekend. Gerard says that this cold trend may continue till the whole of December.
Although it is not always easy to link polar patterns directly to North American weather, this winter storm was preceded by a phenomenon called stratospheric warming over the North Pole. This phenomenon occurs when the stratosphere – the layer of the atmosphere above the troposphere, where most of our weather occurs – suddenly increases in temperature by several degrees. That warming weakened the polar vortex, the cycle of strong winds around the Arctic that surrounds the coldest air around the pole. When it weakens, it can cause cold air to flow southward. Gerard says a second wave of the polar vortex could begin in the next few weeks.
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