On the morning of Monday, December 24, a cold front pushed through the state, and a dry high pressure began to settle into the area, providing fair weather and seasonal temperatures just in time for the holidays. Minimum temperatures started in the mid to upper 30's across much of the region, though the National Weather Service (NWS) stations along the Piedmont observed lows in the upper 20's. Under plenty of sunshine, temperatures warmed into the mid 50's in the Upstate, and closer to 60 degrees near the coast. The tranquil weather continued as high pressure centered over the Carolinas on Christmas morning, with low temperatures in the upper 20's to upper 30's, and not a single snowflake in sight. Visibilities in parts of the Lowcountry and Pee Dee were reduced as shallow fog developed in some of the low-lying areas. As the fog lifted, the Palmetto State observed another dry day with clear skies and high temperatures in the mid to upper 50's.
The calm weather pattern lasted for one more day, as the ridge started to move off the coast on Wednesday, December 26, and onshore flow brought moisture from the Atlantic and Gulf across the state. The next weather system to impact the region was gaining strength in the Central Plains, as it started to pull off to the northeast. As moisture moved back into the region, clear skies gave way to increased cloudiness by mid-afternoon. The combination of the location of a warm front and ridging over the East Coast set up a cold air damming event in the Piedmont and Upstate on Thursday. The high temperature at the NWS station at the Greenville-Spartanburg International Airport was 45 degrees, only 6 degrees higher than the recorded low (39 degrees), while along the coast the station at the Charleston International Airport reported a high of 67 degrees. The warm front began to lift out of Georgia and into South Carolina by Thursday afternoon and shower activity developed along the boundary in the Upstate with isolated showers near the coast.
On Friday morning, CoCoRaHS stations in the Upstate reported over two inches of rain, including the two stations near Salem in Oconee County that had 24-hour rainfall totals of 3.45 and 4.24 inches. During the day, a line of strong slow-moving thunderstorms pushed across the Midlands and prompted a tornado warning over Saluda County. A Saluda County emergency manager reported damage to a home near Saluda; pictures showed a metal building had been moved off the foundation, snapped trees and sections of a metal roof had been peeled off another building. Storm damage was also reported near Silverstreet in Newberry County. Based on the reported damage and finding hardwood trees uprooted and snapped during their survey, the NWS Columbia determined the damage occurred due to estimated wind gusts of 70 to 80 mph associated with a thunderstorm that moved through the county. In the Pee Dee region, trees were snapped and several old buildings sustained roof damage in the Wallace area. The NWS Wilmington sent a team to survey the damage for a possible tornado. Later the same day, thunderstorms produced a wind gust of 40 mph at Fort Sumter as the line continued to move across the state.
On Saturday, December 29, the cold front stalled near the area and lingered through the weekend, providing the atmospheric set up for rain across the Palmetto State through the following week as several upper-level disturbances would cross the region. For the second day in a row, both high and low temperatures were about 15 degrees above normal for this time of year. Low temperatures only dropped to the mid-50's in many locations south of Interstate 20, and high temperatures in the upper 60's to low 70's. The three-day rainfall totals ending the morning of Sunday, December 30, across the state ranged from a low total of 0.44 inches at a CoCoRaHS station in Mount Pleasant to a high of 6.92 inches reported at the NWS station in Jocassee. The heavy rain that fell in the watersheds caused some area rivers to rise, and many were reported to be in minor to moderate flood stage, including the Congaree, Wateree, Savannah, Santee, and Pee Dee. An emergency manager in Georgetown County reported that some elevated homes in Sampit, along the Santee River, had been surrounded by water and a few roads were closed due to flooding. Overnight, the combination of mild temperatures and moisture created dense fog in parts of the Lowcountry and Pee Dee, with reduced visibilities to less than a half a mile. The wet pattern would continue into the first week of the new year.
(Note: The highest and lowest official temperatures and highest precipitation totals provided below are based on observations from the National Weather Service Cooperative Observer network and the National Weather Service's Forecast Offices.)| Weekly* | Since Jan 1 | Departure | |
|---|---|---|---|
| Anderson Airport | 1.36 | 61.81 | 17.7 |
| Greer Airport | 1.35 | 67.62 | 20.6 |
| Charlotte, NC Airport | 1.02 | 58.97 | 17.4 |
| Columbia Metro Airport | 1.65 | 49.49 | 5.0 |
| Orangeburg Airport | 1.16 | 45.50 | -1.1 |
| Augusta, GA Airport | 0.75 | 54.82 | 11.4 |
| Florence Airport | 1.01 | 58.13 | 15.3 |
| North Myrtle Beach Airport | 0.93 | 68.51 | 16.6 |
| Charleston Air Force Base | 0.54 | 57.69 | 6.8 |
| Savannah, GA Airport | 0.99 | 43.01 | -4.9 |
| *Weekly precipitation totals ending midnight Sunday. |
4-inch depth soil temperature: Clinton: 50 degrees. Columbia: 58 degrees. Barnwell: 53 degrees. Mullins: 48 degrees.
Much of the state received at least half an inch of rain over the seven day-period, with isolated locations in the Midlands reporting close to three inches and widespread reports of four to seven inches in portions of the Upstate. With only one day left in 2018, the Central Savannah River Area (CSRA) would remain the driest part of the state for 2018, with annual rainfall totals measuring close to eight inches below normal. Another round of heavy rainfall over the weekend caused some flooding issues in the Upstate, especially in the more mountainous areas. The rainfall from this storm system, combined with rainfall throughout the month, continued to keep rivers high across the state, with some moderate flooding along portions of the major river systems, including the Congaree, Wateree, Savannah, Pee Dee, Little Pee Dee and Santee rivers. Many of these rivers were running at full bank, and continued to report streamflow values that were still much above normal for this time of year.
Charleston Harbor (CHTS1): 59.0 degrees.
Capers Nearshore Buoy (Station 41029): 60.4 degrees.
Fripps Nearshore Buoy (Station 41033): 59.0 degrees.
