Five Things To Know About Wintry Weather in the South

Linda Lam
Published: January 3,2017
Every winter, those that live in the South wonder if any accumulating snow will impact their area, and this year is no exception.
We are watching the potential for snow and ice in the South late this week.
This is the prime time of year for winter storms in this region and cold air is expected to be in place later this week. However, there are some questions regarding how much moisture will be available and how strong the disturbance will be, along with its track. Be sure to check back to weather.com for forecast updates.
(MORE: Winter Storm Helena Forecast)
Snow and ice are not as rare in the South as you may think and when wintry weather does occur it can bring significant impacts.
Here are five things to know about about wintry weather in the South:

1) Three Key Ingredients Are Needed

A few key ingredients need to come together for snow and ice to develop in the South.
First, cold air needs to be in place. This typically happens a few times each winter when the polar jet stream dives southward across the U.S.

Common setup for snow and/or ice in the South.

Second, moisture is necessary for any precipitation to form. The ideal setup would involve the subtropical jet stream to be over the South. This would then allow disturbances to track near the South, which provides the third ingredient of lift in the atmosphere.
If the air is cold enough close to the surface, then snow, sleet or freezing rain can form.
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There are other setups that can produce wintry conditions in the South. One such scenario involves a strong low pressure system that develops near the Gulf Coast or off the Southeast coast. An example of this is the Superstorm of 1993.

2) It's Prime Time

January and February are when winter storms are most common in the South. This is when the ingredients mentioned above are most likely to come together.
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In some years, a cold and active weather pattern can remain in place over the East for periods of time. The combination of arctic air and an active subtropical jet stream can bring multiple rounds of snow and ice to portions of the South.
However, snow can occur in late fall and even in March, like with the Superstorm of 1993.

3) Season Totals Can Be Surprising

Many locations in the South experience snow on average at least once every other snowfall season, which is from July through June.
However, the amount of snow is frequently less than an inch. A few cities that see less than an inch on average each year include Charleston, South Carolina; Jackson, Mississippi; Montgomery, Alabama; and Macon, Georgia. These averages are derived from data for the years 1981-2010.

Average seasonal snowfall for selected Southern cities and the date when at least one inch of snow was measured.

Even though each snowfall event may be less than an inch, over a season the snowfall totals can add up to a decent amount. Raleigh, North Carolina, receives 5.9 inches a season on average each season, while Nashville, Tennessee, sees about 5.0 inches and Atlanta measures just over 2.5 inches. In some higher elevation areas, average snowfall is even higher. Asheville, North Carolina, at an elevation of over 2,000 feet, typically receives 11.6 inches in a season.
(MAPS: Precipitation Forecast)
Some seasons can be particularly snowy and many cities have tallied more than a foot of snow in a season in the past. Huntsville, Alabama measured just over two feet of snow in 1963-64 and Nashville, Tennessee saw 38.5 inches in 1959-60. Farther east, Knoxville, Tennessee recorded 56.7 inches that same season.
As expected, snowfall totals are much  closer to the Gulf Coast. The most snow in a season in New Orleans is only 2.7 inches, which took place in 1963-64 and in Houston the highest seasonal snowfall total is 4.8 inches in 1973-73.

4) Ice Is a Risk, Too

Along with snow comes the threat of ice too. Sleet and freezing rain are fairly common in the South, with many areas seeing wintry precipitation at least once each season.

Icicles form in an unusually chilly Charleston, S.C.
(Steve Colman)

The type of precipitation that falls is due to the temperature profile in the atmosphere. When temperatures are below freezing both near the surface and above the surface, snow is the result.
However, when temperatures close to the ground are below the freezing mark, but the air is warmer a few thousand feet aloft sleet or freezing rain can form. Sleet will fall if precipitation refreezes before it reaches the ground and freezing rain will form if it freezes on contact with a cold surface.
(MORE: 5 Reasons Freezing Rain Is the Worst)
One area where this can commonly occur is in the Piedmont of the Carolinas and northern Georgia. This is due to the cold air banking up against the eastern slopes of the Appalachians, resulting in cold air lingering near the surface.
Heavy amounts of freezing rain accumulations have historically been very impactful for parts of the South, leading to tree damage and widespread power outages in some cases.

5) Little Accumulation Can Bring Big Impacts

Although most of the time the snow and ice amounts are usually on the low side, significant impacts can result.
This is partly due to the infrequent nature of wintry episodes in the region. Motorists do not usually have much experience driving in winter weather and most areas do not have a large fleet of equipment to treat roadways.

In this aerial photo, abandoned cars at I-75 headed northbound near the Chattahoochee River overpass are piled up in the median of the ice-covered interstate after a winter snow storm, Wednesday, Jan. 29, 2014, in Atlanta.
(AP Photo/David Tulis)

Consequently, roads can become treacherous quickly, so it is necessary to be prepared for dangerous travel and the closure of businesses.
In January 2014, parts of the South were impacted from one of the most recent memorable storms, Winter Storm Leon, which left people stranded in vehicles across the Atlanta area.
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Hopefully, lessons from past winter storms will help to mitigate future impacts.

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