Monday, February 11, 2013

Remembering The 1973 Snowstorm In South Carolina

February 9-10, 2013 marked the 40th anniversary of the greatest snowstorm to hit South Carolina in modern times.  Snow in the South is rare enough, but this set many records across the states of Georgia and South Carolina.  Here are some of the notable snowfalls from the storm:

                        Rimini, SC                              24 inches
   Macon, GA                            19 inches
                        Branchville, SC                      19 inches
                        Lake City, SC                         17.5 inches
                        Blackville, SC                         17 inches
                        Columbia, SC                         16 inches
                        Aiken, SC                               15 inches
                        Summerville, SC                    15 inches
                        Springfield, SC                       15 inches
                        Kingstree, SC                         13 inches
                        Camden                                 12 inches

These are just a few of the totals from this remarkable storm.  Generally the snowfall was between 10 to 20 inches over much of central Georgia and central and southern South Carolina.  Winds will strong enough to produce drifts to 5 feet in Sumter and Clarendon counties.

Many refer to this storm as a blizzard and to many in the South it seemed like one.  However, I could not find evidence that it met the criteria for one.  No doubt it was a significant snowstorm which would rival storms much farther north.

Timing is everything for snowstorms in the Deep South.  Typically when it gets cold enough to produce snow the air is too dry.  The right mix of cold air, moisture, and intensifying storm are rare.  Thus, forecasting such storms is quite challenging.

The challenge was much greater back in 1973.  Knowledge about the dynamics of such storms and the modern technology to forecast them was not as advanced as today.  Geostationary satellites were not in standard use or available to local forecasters.   It would not be until the 1980s that much of the dynamics would be known and satellites would be commonplace for forecasters.  The forecast of the New England blizzard this past weekend, days ahead, would have been impossible back then.

Yet the 1973 snowstorm followed a pattern typical for Southeast snowstorms.  In the upper atmosphere a trough was digging far to the south over the central U.S.  At the same time a weak disturbance was moving east across the Southwest.  The two phased together to form an impressive low pressure system aloft.

The upper-level pattern at 500 mb for 7 a.m. (12z) on Saturday, February 10, 1973.  The first trough helped to pump abundant moisture into the cold air for heavy snow to occur.  Click on the image for a larger view.  Image Credit: NOAA/NWS.

At the surface a cold front had pushed into the Gulf of Mexico creating a thermal boundary and a zone of instability. Moisture began streaming northward as the upper-level system approached and intensified.  Precipitation began to fall early on Friday, February 9.  Notice the snow falling in San Antonio, Houston, and Lake Charles on the map for Friday morning.

The surface maps for 7 a.m. on Friday, February 9 and Saturday February 10, 1973.  Note the snow falling in San Antonio, Houston, and Lake Charles on the top map.  Heavy snow fell overnight from central Georgia to southeast North Carolina.  Click on either image for a larger view.  Image Credit: NOAA/NWS.

A surface low formed on the front in the Gulf early in the afternoon (18z) and began to move northeastward.  Snow began to spread east into Alabama, Georgia, and then South Carolina.  The snowfall was light at first, but then the snowfall increased Friday night into Saturday morning.  This was because as the upper-level disturbance approached it intensified the surface low helping to pump even more moisture into the region.  In addition, the surface low was drawing more cold air into the areas to the north changing the precipitation to snow.

Heavy snow was reported overnight from Macon, GA to the Carolina coast.  Winds increased as the surface low strengthened.  This set the stage for drifting snow which helped shut down interstates in the region.  The National Guard was called out to rescue motorists stranded on I-95 particularly in Sumter and Clarendon counties.  Thousands of roofs collapsed from the weight of the heavy snow.

Snowstorms always have a quirk to them.  Consider that the snow did not extend much into northern Georgia or the upstate of South Carolina.  In fact, Atlanta received only a trace of snow whereas Macon, 60 miles to the south, received 19 inches.  Farther south, Tallahassee received an inch of snow to the delight of some residents who had never seen snow.

South Carolina winters were getting colder from 1912 to about 1972.  They have warmed significantly since that time.  Click on the image for a larger view.  Image Credit: Climate Central.

It is also interesting that this snowstorm occurred at a time when South Carolina was seeing some of its coldest winters.  The graph above shows that winters were getting colder from 1912 to about 1972.  Winters have warmed significantly since then.  That does not mean that such a storm could not happen again.  Again, it depends of the timing of cold air, moisture, and intensifying storm system.

I leave you with two Youtube videos of the snowstorm’s aftermath.  The first one is from Sumter, SC where some of the heaviest snow fell.  The other is from Macon, GA.  Enjoy!