Five inches of snow fell in central South Carolina this weekend, with flurries even reported on the coast in Charleston. One week ago today, The Vane covered the potential for a significant snowstorm in the northeast, but nobody quite expected this. Here's what happened.

For the past couple of days, the news has breathlessly reported on the heavy snow that impacted the Appalachian Mountains from West Virginia through Georgia on Saturday, producing nearly two feet of snow on some of the highest peaks. It's not the earliest snowfall on record for the mountains, but in some spots, it was the largest amount recorded so early in the year.

Snow also fell in one unexpected location—central South Carolina. The state's capital, Columbia, sits dead-center in the state, and some of the city's western suburbs saw up to five inches of snow as the storm moved through. It's safe to say that the intensity of the storm took forecasters by surprise, since the weather models didn't show snow outside of the mountains even as the wintry precipitation fell in the middle of the Palmetto State.

What happened?

Last week, the models showed a nor'easter developing near or just off the coast of the northeast, bringing rain to coastal cities and snow to interior parts of the region. The models differed greatly on who would see what—one model showed the heaviest snow falling from Syracuse (in the middle of New York) northeast through Maine, while another showed it falling closer to Albany and Westchester County.

As always, especially so far in advance of a storm, this disclaimer appeared several times through the post and proved useful when the storm hit: "Again, all of this information can and probably will change as the we draw closer to the weekend and the models get a better handle on what the atmosphere will do."

Boy, did things change.

It did snow, and some of it did fall in the northeast. Bangor, Maine reported 12.0" of snow on Sunday, breaking their record for the most snow to fall so early in the year. However, the jet stream dipped much further south than the models were showing five days in advance, and this caused the storm to form in the southeast instead of closer to New England.

This is what the jet stream looked like on Saturday morning, featuring a large, sharp trough that shot down straight into southern Florida.

Embedded within this trough was an upper-level low—a cold-core low that forms around the 500 millibar level, or around 18,000 feet above sea level—which was responsible for both the heavy snow in the mountains and the surprise snowfall around Columbia, South Carolina. The upper-level low is shown below.

As they're indicative of cold air in the atmosphere, upper-level lows are notorious for, among other things, producing surprise snowstorms. The cold air through the atmosphere over central South Carolina allowed the rain to change over to snow, and with temperatures at or near freezing at the surface, the snow was able to accumulate rather quickly.

At 7:44AM, the National Weather Service office in Columbia, South Carolina issued a winter weather advisory for counties between Columbia and Augusta, Georgia in anticipation of "rain mixed with snow showers" producing less than one inch of snow. The product served as a travel advisory, letting folks know that the roads could be slippery.

Over the next couple of hours, up to five inches of snow covered every exposed surface outdoors, bringing traffic to a halt and knocking out power as trees fell on lines. The above snowfall analysis from NOAA shows between two and four inches of snow on the ground from Greenville to Columbia at 10:00 AM.

The photos from the ground are either photogenic or nightmarish, depending on your stance on winter weather.

How unprecedented was this storm? The airport in Columbia—on the southwest edge of town—reported a trace of snow during the event, marking the seventh time that a trace* of snow was reported in the city during the month of November since the station began operating in 1948.

An official reporting station southwest of Columbia in a town called Pelion officially reported 4.0" of snow on November 1, marking the second time the station has reported snow during the month of November (the other was a trace in 2006), and the earliest measurable snowfall since the station opened in 1948.

Significant snow falling on November 1 in central South Carolina was an unprecedented event that resulted from the rare confluence of several snow-positive factors. If you hate snow, don't fret—this isn't an omen of the winter to come. To put it in technical terms, this was a freak thing.

*A "trace" of snow, often denoted by a "T," is defined by the National Weather Service as snow that melts when it lands.

[Images: The State Newspaper via Twitter, WeatherBELL x2, NOAA]

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