April 3, 2019

An Intense April Nor'easter Produced Atlantic Supercells And Snow In The Carolinas

A powerful nor'easter developed off the eastern coast of the Carolinas on Tuesday, bringing a burst of winter weather to a part of the country that hasn't seen much of it this year. The formation and track of the nor'easter has been in the forecast for a few days now, but this storm turned out to be particularly impressive due to its structure and the supercells it produced over the open ocean.

The unusual snow in the Carolinas was the storm's major headline for most of the day. Subfreezing temperatures just above the ground allowed frozen precipitation to reach the surface for a couple of hours from north-central South Carolina to north-central North Carolina. Folks around Charlotte saw the most, with some communities pleasantly surprised to measure about two inches of snow by the time the precipitation came to an end. Snow and sleet accumulated on cars as far north as Greensboro, while it was just pretty to look at closer to the Virginia border where I live.

The snow was mostly conversational and didn't cause too many problems thanks to warm ground temperatures and air temperatures that mostly stayed above freezing during the event. Charlotte only dropped to 36°F during the heaviest precipitation.

It's not common to see accumulating snow this far south this late in the year. This is just the second time in the past century that Charlotte has seen measurable snow during the month of April. Winter weather usually comes to an end across the Carolinas by the middle of March, though there are some exceptions. Parts of North Carolina saw accumulating snow during the second week of April last year, followed a few days later by a severe weather outbreak.

Source: Gibson Ridge

Things got even more interesting once the storm fully exited the North Carolina coast. The low-pressure system that would go on to become a full-fledged nor'easter quickly got its act together this afternoon thanks to a sharply tilted upper-level trough and favorable winds in the jet stream. Meteorologists started buzzing on social media this evening while watching the radar out of Morehead City, NC, as a squall line with multiple embedded supercells played out a few dozen miles off the Outer Banks.

I mean, helloooo:

Those thunderstorms actually wound up helping the low-pressure system deepen even faster than it would have otherwise. For a couple of hours this afternoon, this storm strengthened in part through the same processes that fuel tropical and subtropical cyclones. Strong updrafts in the thunderstorms near the center of the low pulled lots of air away from the surface, causing the minimum central pressure to deepen more rapidly than it would have otherwise. NOAA's Weather Prediction Center put it succinctly this evening: "[the storm is] a good reminder that cyclones exist along a continuum and that determining their type (extratropical, subtropical, or tropical) isn't always clear."

New England will see some gusty winds and a cold rain on Wednesday morning as the bulk of the storm passes the region to the east. Atlantic Canada will feel the full brunt of the storm as it makes landfall in Nova Scotia on Wednesday evening. Environment Canada has warnings out for wind gusts as high as 60 MPH along Nova Scotia's southern coast and 2-3 inches of rain across the province through Thursday. The storm will be somewhat kinder to New Brunswick and Prince Edward Island, bringing an inch or two of cold rain with some heavy snow possible on the western fringe of the storm.

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I graduated from the University of South Alabama in 2014 with a degree in political science and a minor in meteorology. I contribute to The Weather Network as a digital writer, and I've written for Forbes, the Washington Post's Capital Weather Gang, Popular Science, Mental Floss, and Gawker's The Vane. My latest book, The Skies Above, is now available. My first book, The Extreme Weather Survival Manual, arrived in October 2015.