The December 19th, 2000 Winter Storm
Bryan P. McAvoy
Author's Note: The following report has not been subjected to the scientific peer review process.
The map below shows snowfall totals reported from the 19 December 2000 winter storm for WFO Greenville-Spartanburg's County Warning Area (CWA). Amounts of four inches or more meet winter storm criteria, and are lightly shaded. The map represents snowfall amounts as they were reported to the office during the event, and may not represent storm total accumulations, though they should be close.
Figure 1. Total snow accumulation (inches) for the 19 December 2000 winter storm. Click on image to enlarge.
A winter weather advisory was issued for the entire Greenville-Spartanburg CWA during the 4 AM EST forecast package on 19 December. However, advisory criteria or better were only reached in the northwestern half of the CWA and in a small part of Davie County, North Carolina. Areas further south and east had only rain for most of the event, with only some light snow that evening. The advisory was upgraded to a winter storm warning around 530 AM EST on the 19th for parts of the mountains of northeast Georgia, South Carolina and southern North Carolina after reports of snowfall amounts exceeding four inches started coming in from northeast Georgia. In these areas, two narrow bands of heavy snow developed during the early morning hours. As the second band slowly moved east into the Upstate, it rapidly dissipated by 8 AM EST, making it no further east than western Spartanburg County.
The image below is a model sounding valid at noon local time on the 19th for Charlotte, one of the locations in the advisory which received almost no measurable snowfall. The red line is a temperature trace. Notice how the red trace starts right at zero degrees Celsius and stays there up through about the lowest 4000 feet. In actuality, the surface temperature was warmer (see the surface map below) than the sounding indicated.
Figure 2. Eta forecast sounding from the 0000 UTC 19 December run of the Eta model valid at 1700 UTC on 19 December. Click on image to enlarge.
The map below was valid at 1 pm local time on the 19th. The observation near the center of the map, with the designator KCLT, is that from Charlotte Douglas International Airport. This is one hour later than the model sounding above (the temperature/dewpoint was the same the previous hour). The temperature at Charlotte verified a little over 2 degrees Celsius warmer than what the model projected. It is interesting to note that the model depicted above, the 0000 UTC 19 December run of the Eta model, generated 0.28 inches of rain at Charlotte during the late morning and early afternoon. In reality, only 0.10 inches of rain fell during this time. It is quite possible that the lighter than expected precipitation rates resulted in a warmer than anticipated layer in the lower atmosphere, leading to mostly rain in the North Carolina Piedmont and the eastern part of Upstate South Carolina. These model errors apparently were exacerbated further east in the Carolinas. As these locations are outside of our forecast area, they were not investigated.
Figure 3. Surface front and pressure analysis at 1800 UTC on 19 December.