With confidence increasing that a significant event was likely, GSP began making plans to augment staffing for 15 March.įigure 3. Meanwhile, GSP continued to highlight the potential for a severe weather outbreak in the HWO issued at 0936 UTC on 13 March and specifically mentioned areas south of Interstate 85 as being the highest threat area. 3) featured a slight risk for severe weather across much of the Southeast. The SPC Day 3 Convective Outlook, issued at 0722 UTC on 13 March (Fig. The Hazardous Weather Outlook (HWO) issued by GSP at 0925 UTC on 12 March specified that the Piedmont and Foothills of the western Carolinas and northeast Georgia were the most likely areas to receive severe weather on Saturday, 15 March. Subsequent model runs of the GFS continued to indicate the potential for an outbreak of severe weather on 15 March, increasing forecasters? confidence that a significant event would occur. This results in significant weakening of mid-level lapse rates, and therefore weaker potential instability. This is due to the fact that convection often significantly modifies (moistens and warms) this layer before it reaches Georgia and the Carolinas. Due to the high degree of potential instability in the sounding, removal of the cap often results in explosive convective development, hence the term "loaded gun." It is quite rare for the elevated mixed layer to advect much further east than the lower Mississippi Valley (Lanicci and Warner, 1991). This inversion inhibits or "caps" convective development. As this warm, dry air overspreads relatively cool, moist maritime air originating from the Gulf of Mexico, a strong inversion becomes established at the top of the marine layer. This layer is referred to as the "elevated mixed layer." Originating from the warm and dry high-elevation regions of northern Mexico, strong southwest flow in the 5,000 to 10,000 feet layer often advects this airmass north and east over the southern Great Plains and lower Mississippi Valley during Spring. One of the important characteristics of this sounding that contributes to its strong potential instability is the layer of steep, nearly dry-adiabatic lapse rates that exists above the moist boundary layer. 2) often associated with Great Plains supercell outbreaks.įigure 2. The Area Forecast Discussion issued by GSP at 1800 UTC mentioned the resemblance of forecast soundings from the National Centers for Environmental Prediction?s (NCEP) Global Forecasting System (GFS) model to the "loaded gun" sounding (Fig. The possibility of a significant outbreak of severe weather occurring on 15 March 2008 within the GSP County Warning and Forecast Area (CWFA) was first identified by GSP forecasters on 11 March. To convert to EDT, subtract four hours from the UTC time. Note that all times in this report are referenced to Coordinated Univeral Time (UTC), which is four hours ahead of Eastern Daylight Time (EDT). Black squares represent reports of wind gusts of 65 knots or greater, while black triangles are reports of hail 2 inches in diameter or larger. Tornado reports are shown in red, large hail reports are shown in green, and damaging wind reports are shown in blue. Preliminary SPC storm reports for 15 March 2008. Nevertheless, the severe weather episode was well-forecast several days in advance by the National Weather Service (NWS) Weather Forecast Office (WFO) at Greenville-Spartanburg (GSP) and by the NWS Storm Prediction Center (SPC).Ĭlick here for a list of storm reports from this eventįigure 1. This was an unusual event for the region, as the atmospheric ingredients necessary for supercell thunderstorms rarely coexist across northeast Georgia and the western Carolinas. The other two tornadoes affected Franklin and Hart counties in Georgia, and northeast Abbeville County in South Carolina, and were rated at EF0 intensity. In addition, three tornadoes were confirmed, the strongest being the EF2 tornado that tracked over southeast Elbert County, Georgia. Numerous reports of large hail were received, including one report of softball size hail in Anderson County, South Carolina.
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On 15 March 2008, a series of supercell thunderstorms produced a significant outbreak of severe weather across Upstate South Carolina and northeast Georgia (Fig. Image courtesy of, photographer unknown.Īuthor's Note: The following report has not been subjected to the scientific peer review process. Numerous reports of hail and wind damage were received from Abbeville County and a tornado touched down near Due West. A supercell thunderstorm moves through Abbeville, South Carolina, on Saturday 15 March 2008.
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