The South’s First Winter Storm Explained

The storm near peak intensity on Monday, November 28, 2016. Image credit: NOAA

The season’s first vigorous winter storm came to life over the northern Plains at the end of November and left a trail of destruction in its wake. The air pressure at the center of this photogenic low-pressure system dipped to the strength of a formidable hurricane—bottoming out at 974 millibars on Monday, November 28, 2016—allowing the storm to unleash a slew of deadly weather from the Dakotas to Alabama.

FALL’S FIRST TORNADO OUTBREAK

At least five people were killed on Tuesday, November 29, when more than two dozen tornadoes touched down in parts of the southeastern United States. The storms developed in Mississippi early in the day on Tuesday and steadily marched across Alabama and Tennessee through the night-time hours.

Three of the people who died on Tuesday were caught in a mobile home during a tornado in Rosalie, Alabama. A mobile home is just about the worst place to take shelter from a tornado. These structures are not built to withstand intense thunderstorms or tornadoes; according to the National Weather Service, it only takes winds of about 100 mph to severely damage or destroy a mobile home.

We’re used to hearing about tornadoes in the South during the spring months, the time traditionally known as tornado season, but the late fall and early winter actually marks the beginning of a secondary tornado season, due to intense storms like the one we saw at the end of November. Warm and humid air surging north from the Gulf of Mexico set the stage for intense thunderstorms to develop. Once a strong cold front helps lift the unstable air skyward, storms gather strength. On November 29, powerful winds changing speed and direction through the atmosphere gave the thunderstorms the twist they needed to spawn tornadoes, damaging winds, and hailstones as large as baseballs.

NORTH DAKOTA SNOWSTORM

On the colder side of things, the storm system dumped up to 2 feet of snow across parts of the Plains and Rocky Mountains on November 28 and 29. North Dakota caught the brunt of the winter weather, with much of the sparsely populated state picking up between one and two feet of snow. A resort in the northwestern part of the state measured two feet of snow, and the state capital of Bismarck, near the center of the state, saw 18 inches of snow by the time the skies cleared.

Residents of the northern Plains are used to snow, but not this much all at once. This was the 10th-largest snowstorm since records began in Bismarck back in 1886. It seems early for the rest of the country, but November is a busy time for snow in North Dakota—in an average year, both Bismarck and Fargo receive about half a foot of snow during the month of November. In fact, five of the 10 biggest snowfalls ever recorded in Bismarck occurred during the month of November.

Even though this storm creeped its way into the records, local news reports that it didn’t cause too many problems around the state, aside from some school, business, and road closings. That may be because North Dakota is the fourth-least populous state in the United States—though it’s also the fastest-growing state in the country due to the oil boom on the Bakken Formation in the northwestern part of the state.

TENNESSEE FIRESTORM

The ongoing drought in the southeastern United States is taking its toll on forested areas, with even the tiniest spark setting off raging infernos that can quickly spiral out of control. A massive fire burned through two popular resort towns in the eastern Tennessee mountains on November 30, killing several people and destroying hundreds of homes and businesses. Though the weather wasn’t directly responsible for the fires that tore through Gatlinburg and Pigeon Forge, the same storm system that caused tornadoes in the south and near-blizzard conditions in the north also helped this fire spread out of control.

A tight pressure gradient caused by the strengthening low-pressure system over the Plains caused winds to rip out of the south across the southeast on the 28th. A fire burning on Chimney Tops Mountain grew exponentially as a result of the intense winds, rapidly spreading down into the valley near Gatlinburg and Pigeon Forge.

The wildfire came into the towns so quickly that residents and visitors had to scramble to leave. Some didn’t make it out in time. Guests at Gatlinburg’s Park Vista hotel were trapped inside as flames lapped at the windows, their only escape route down the mountain cut off by fire. Firefighters were able to beat back the flames enough to evacuate the hotel’s guests, but not everyone in the area was so lucky. Authorities report that at least four people in Sevier County, Tennessee, died as a result of the flames, though that total could climb as rescue crews continue to search the remains of homes and businesses.

Fortunately, heavy rain followed just behind the rapid spread of the fires, moistening the dry vegetation and stopping the rapid spread of the flames, staving off potentially an even greater catastrophe.