Unsettled and unseasonably warm weather started the period on Monday, December 9. Scattered showers were reported across the state, with high temperatures ranging from the mid-50s in the Upstate to the upper 60s elsewhere, up to ten degrees above normal. Tuesday morning lows were up to twenty-five degrees above normal, with temperatures in the upper 50s to lower 60s and daytime highs reaching the upper 60s to mid-70s. Moderate and heavy rain were reported in portions of the Upstate and Midlands late on Tuesday as a strong cold front pushed through the region
By Wednesday morning, CoCoRaHS observers in portions of Oconee, Pickens, and Greenville counties had received up to 3.50 inches. The front moved through the state on Wednesday slowly, and windy conditions developed behind the front, prompting lake wind advisories for most of the Midlands and parts of the Coastal Plain. There was a non-thunderstorm wind gust of 40 at the National Weather Service (NWS) station at Charleston International Airport, and an anemometer at Folly Beach recorded sustained winds of 35 with a gust of 49 mph just before the cold front passed over the area. High temperatures for Wednesday were set early in the morning and dropped throughout the day.
A strong Canadian high pressure built over the Northeast on Thursday, bringing cooler and drier weather into the region. Morning temperature dropped below freezing, and despite clear skies, daytime temperatures struggled to reach the mid-50s on Thursday and Friday. Temperatures moderated over the weekend, with increasing cloud cover as moisture returned to the area ahead of an approaching system. Also, over the weekend, the tidal levels at the Charleston Harbor gauge ranged between 7.14 and 7.20 feet MLLW, causing shallow saltwater flooding in low-lying coastal areas.
(Note: The highest and lowest official temperatures and highest precipitation totals provided below are based on observations from the National Weather Service (NWS) Cooperative Observer network and the National Weather Service's Forecast Offices.)| Weekly* | Since Jan 1 | Departure | |
|---|---|---|---|
| Anderson Airport | 3.06 | 51.68 | 7.6 |
| Greer Airport | 3.84 | 54.28 | 7.0 |
| Charlotte, NC Airport | 2.37 | 50.38 | 8.7 |
| Columbia Metro Airport | 1.10 | 50.35 | 7.2 |
| Orangeburg 2 (COOP) | 0.81 | 51.70 | 3.5 |
| Augusta, GA Airport | 1.01 | 47.61 | 5.7 |
| Florence Airport | 1.00 | 44.96 | 2.4 |
| North Myrtle Beach Airport | 0.22 | 45.06 | -1.8 | Charleston Air Force Base | 0.37 | 50.63 | -0.1 |
| Savannah, GA Airport | 0.22 | 54.78 | 8.3 |
| *Weekly precipitation totals ending midnight Sunday. M - denotes total with missing values. s - denotes total with suspect data. |
4-inch depth soil temperature: Clinton: Not Available. Columbia: 52 degrees. Barnwell: 49 degrees. Mullins: 48 degrees.
More than two inches of rain was reported for most locations in the state north and west of the Interstate 20 corridor, with a swath of heavier rain, up to three inches in parts of Fairfield, Newberry, and Saluda counties. Areas north of the Interstate 85 corridor recorded up to five inches of rain, with most precipitation falling overnight Tuesday through Thursday morning. While rain fell across the Coastal Plain, totals ranged from close to an inch in interior portions to less than a quarter of an inch near the coast. The U.S. Drought Monitor map released on Thursday, December 12, showed an expansion of moderate drought (D1) designations in the Upstate due to the lack of rainfall during the previous periods. Any changes in the USDM drought designations from rainfall during the latter half of the period will be reflected in the map released on Thursday, December 17, because it fell after Tuesday morning's data cutoff.
With higher amounts of rain falling in the headwaters of the Santee and Savannah basins, the 14-day average streamflow values at most gauges rose to normal, with some gauges reporting flows above normal. Values dropped to average across the ACE Basin and Lower Savannah River watershed; however, due to the continued lack of rainfall during the past periods, the values at gauges in the Pee Dee River basin dropped to below normal values. The river height levels along the Congaree and Santee rivers and the tidal gauge at the Charleston harbor rose into action and minor flood stage during the period.
