Rare thundersnow is hitting New York — here's what that is and why it happens

  • Snowfall rates were picking up for the storm hitting the Northeast on Wednesday.
  • The National Weather Service said there may be thundersnow: a rare meteorological phenomenon in which a storm involving thunder and lightning also drops snow.
  • Not long after noon ET, it happened.
  • That's rare because the storms that drop snow are usually different from the storms that cause thunder and lightning.

While dropping snow and rain throughout the Northeast, the second nor'easter to strike in March also produced the rare event known as thundersnow.

The New York office of the National Weather Service had announced earlier Wednesday morning that the region may see the uncommon meteorological phenomenon later in the day.

"During the time of the heaviest snowfall this afternoon, thundersnow is a possibility," NWS New York said on Twitter. "Snowfall rates of 1-2' per hour, with locally higher rates (2'+per hour) are also possible primarily after noon within the heaviest snow bands."

New Yorkers got to experience the thundersnow's start shortly after noon ET.

The term thundersnow describes a storm with thunder and lightning that also drops snow. Such events are rare because the storms that drop snow are usually very different from the storms that cause thunder and lightning.

See photos from last week's nor'easter: 

14 PHOTOS
Nor'easter slams US East Coast
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Nor'easter slams US East Coast
SCITUATE, MA - MARCH 02: A flooded out road with a stop sign as a large coastal storm bears down on the region on March 2, 2018 in Scituate, Massachusetts. A nor'easter is set to slam the East Coast on Friday, bringing coastal flooding, heavy snow and strong winds to the area. (Photo by Scott Eisen/Getty Images)
NEW YORK, NY - MARCH 02: A person struggles with their umbrella during a large storm on March 2, 2018 in New York, New York. A nor'easter is set to slam the East Coast on Friday, bringing coastal flooding, heavy snow and strong winds to the area. (Photo by Stephanie Keith/Getty Images)
QUINCY, MA - MARCH 2: Daniel Cunningham, 22, of Quincy kayaks out to check on a stranded driver in the flooded Squantum section of Quincy, MA during a nor'easter storm on March 2, 2018. (Photo by Stan Grossfeld/The Boston Globe via Getty Images)
MARSHFIELD, MA - MARCH 2: Waves slam into ocean front homes and surge down Ocean Street where an abandoned Jeep sits in a storm-created ditch at the intersection with Franklin Street in Marshfield, MA during a nor'easter storm on March 2, 2018. (Photo by Barry Chin/The Boston Globe via Getty Images)
QUINCY, MA - MARCH 2: An evacuation takes place on Post Island Road in Quincy, MA during a nor'easter storm on March 2, 2018. (Photo by John Tlumacki/The Boston Globe via Getty Images)
Rubble rests on top of a car after a partially burnt building collapsed due to strong winds in Northeast Washington, DC, on March 2, 2018. A major winter storm pounded the US East Coast on Friday, whipping up strong winds and dumping heavy rain and snow, forcing the cancellation of several thousand flights and the closure of federal government offices in Washington. Coastal flooding alerts were issued from New Jersey to Massachusetts with winter weather advisories, winter storm warnings and high wind warnings in effect from the Northeast to the Mid-Atlantic, the National Weather Service said. / AFP PHOTO / NICHOLAS KAMM (Photo credit should read NICHOLAS KAMM/AFP/Getty Images)
TAKOMA PARK, MD - MARCH 02: High winds downed a tree onto power lines, blocking the street and damaging a vehicle March 2, 2018 in Takoma Park, MD. Freezing temperatures and wind gusts up to 70 m.p.h. pounded the Washington, DC, area, downing trees, knocking out power and forcing schools and the federal government to close. (Photo by Chip Somodevilla/Getty Images)
BOSTON, MA - MARCH 2: A pair keep dry by standing atop a garden planter on a flooded Long Wharf in Boston during a nor'easter storm on March 2, 2018. (Photo by David L. Ryan/The Boston Globe via Getty Images)
MARSHFIELD, MA - MARCH 2: Water surges down Ocean Street in Marshfield, MA past an abandoned Jeep during a nor'easter storm on March 2, 2018. (Photo by Barry Chin/The Boston Globe via Getty Images)
A worker cuts a tree that had fallen on to a house as a storm bringing high winds passes over Kensington, Maryland, U.S., March 2, 2018. REUTERS/Joshua Roberts
American flags partially torn from their poles fly as a storm producing strong winds passes through Washington, U.S., March 2, 2018. REUTERS/Joshua Roberts
A flight information board shows cancelled flights as a storm bringing high winds passes over Reagan National Airport in Washington, U.S., March 2, 2018. REUTERS/Joshua Roberts
SCITUATE, MA - MARCH 2: Waves crash against homes in Scituate, MA during a nor'easter storm on March 2, 2018. (Photo by Jonathan Wiggs/The Boston Globe via Getty Images)
Rubble rests on top of a car after a partially burnt building collapsed due to strong winds in Northeast Washington, DC, on March 2, 2018. A major winter storm pounded the US East Coast on Friday, whipping up strong winds and dumping heavy rain and snow, forcing the cancellation of several thousand flights and the closure of federal government offices in Washington. Coastal flooding alerts were issued from New Jersey to Massachusetts with winter weather advisories, winter storm warnings and high wind warnings in effect from the Northeast to the Mid-Atlantic, the National Weather Service said. / AFP PHOTO / NICHOLAS KAMM (Photo credit should read NICHOLAS KAMM/AFP/Getty Images)
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As Greg Forbes, an expert in severe weather, explained for The Weather Channel, normal thunderstorms tend to be tall, narrow storms with quickly rising air. Snowstorms are usually marked by large, extensive, shallow, and flat clouds with gentle upward and downward motion.

When a snowstorm develops a more intense upward lift of air, that can lead to thundersnow. The phenomenon is most common in places where geographical features like lakes or mountains create turbulence that can lead to unstable weather systems, which in turn force "turrets" of clouds to rise upward.

High enough up in the atmosphere in those cloud turrets, cold temperatures can mean that both snowflakes and small hailstones form at the same time, according to Forbes. The interaction between snow and hail particles can create electrical charges. At a large enough scale, you start to get lightning — and the thunder that follows it.

In such situations, you also get a lot of snow forming very quickly, which can lead to lots of accumulation.

Thundersnow is more common in lake-effect storms, which is why it's seen more frequently around the Great Lakes. But it can also happen in extratropical cyclones (which are swirling storms outside tropics, like nor'easters).

Thundersnow or not, it looks as if accumulation rates are picking up for this storm. Stay dry and stay warm.

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