WEEKLY SOUTH CAROLINA WEATHER 2018

September 17, 2018 - September 23, 2018

WEATHER SUMMARY:

The week started off with Tropical Depression Florence slowly moving through the Upstate, leaving behind excessive rainfall across the Yadkin-Pee Dee River Basin, and damage along the South Carolina coast.

Rain continued to fall across the Midlands, Pee Dee and Upstate regions during Monday, September 17. That morning, multiple National Weather Service (NWS) Cooperative Stations broke 24-hour rainfall records that were set back on September 17, 1945. These stations included Catawba with 3.51 inches (1.19 inches in 1945), Ninety Nine Islands measured 3.39 inches (3.05 inches in 1945) and Cheraw reported a staggering 9.84 inches (3.80 inches in 1945). In addition to the precipitation values reported by the official NWS stations, two CoCoRaHS observers in Loris, SC, reported 24-hour rainfall totals over 11 inches, ending on the morning of September 17. On the same morning, ten NWS stations broke or tied their highest minimum temperature, including the Charleston International Airport, which recorded a low of 78 degrees, breaking the old record of 75 degrees in 1980.

With Florence’s departure from the area on Tuesday, September 18, summerlike temperatures combined with humid conditions to create heat index values near 105 degrees in portions of the Lowcountry and Midlands. The NWS station at Beaufort MCAS reported a maximum temperature of 95 degrees on both September 18 and September 19, breaking the records set in 2005 (94 degrees) and 1978 (93 degrees), respectively. The Pee Dee River near Cheraw crested at 46.60 ft, marking the third highest crest on record for the river gauge at that location. A weak frontal boundary crossed the state on Wednesday, September 19, ushering into the Carolinas a drier air mass and squashing the chances for widespread rain, though isolated showers caused localized amounts of up to 1.5 inches in Beaufort County and about half an inch in Oconee County.

Behind the front, high pressure moved into the region on Thursday, September 20, and remained in control of the weather into the weekend. The drier air and clear skies allowed for strong radiational cooling and morning low temperatures ranged from the lower 60’s in the more mountainous parts of the Upstate to the lower 70’s near the coast. Based on rainfall and river stages across the state, the U.S. Drought Monitor removed all indication of moderate drought and dry conditions from the Pee Dee and northern Midlands. However, dry conditions were added to areas near the Central Savannah River Area and Lowcountry that did not receive any substantial rainfall from Hurricane Florence.

On Friday, September 21, the floodwaters from Florence continued to move through the Pee Dee, Little Pee Dee and Waccamaw rivers. The Pee Dee River crested near Florence at 61.01 ft., and at Pee Dee at 31.83 ft., less than 2 ft. lower than the record crest of 33.3 ft set in 1945. The Little Pee Dee reached a crest of 54.56 ft. near Nichols on September 20, but the river had risen to 54.48 ft. by September 19 and remained above 50 ft. until late on September 23. The Waccamaw River rose rapidly near Longs, going from a stage of 13.14 ft. on Monday to 20.15 ft. by Friday. The river finally crested at 20.93 ft on September 23, nearly ten days after Hurricane Florence made landfall in North Carolina.

Ahead of an approaching cold front on Saturday, September 22, a high pressure weakened and moved offshore, allowing for a more southerly flow to bring moisture back into the state. Both high and low temperatures were more than 5 degrees above normal in many locations in the Upstate and Midlands on both Saturday and Sunday, with the highs reaching the mid-90's and lows dropping to the upper 60's.

(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.)
The highest temperature reported was 98 degrees on September 18 in Little Mountain in Newberry County.
The lowest temperature reported was 60 degrees at Table Rock in Pickens County on September 18 and Ninety Nine Islands in Cherokee County on September 19.
The maximum 24-hour precipitation reported was 9.84 inches at the National Weather Service Station in Cheraw ending at 7:00 a.m. on September 17. This is the second highest 24-hour rainfall total ever recorded at the station. The maximum 24-hour rainfall record is 10.75 inches recorded on September 16, 2018. The previous record value was 9.38 inches on July 15, 1916.
The CoCoRaHS Station Loris 1.4 ENE (SC-HR-33) reported a 24-hour precipitation total of 11.68 inches, ending at 7:00 a.m. on September 17.
The state average precipitation for the seven-day period was 0.30 inches.

PRECIPITATION:

SOIL TEMPERATURES:

4-inch depth soil temperature: Clinton: 74. Columbia: 80 degrees. Barnwell: 74. Mullins: 70 degrees.

RIVER STAGES:

The week started off with low streamflow values near or above record values due to the rainfall totals from Hurricane Florence. The only area of South Carolina to receive measurable rainfall during the week was the southern Midlands, with rainfall totals up to 3 inches in localized areas near Sumter, St. Matthews and over the Congaree National Park. The rainfall from Florence mainly fell in the Pee Dee Region; areas of the Midlands did not receive any beneficial rain to help combat the long-term dry conditions. The lack of rainfall and dry conditions across the rest of the state caused some streamflow values to drop back to below normal, especially in portions of the Central Savannah River Area, going into the week of September 24.

COASTAL OCEAN TEMPERATURES:

Charleston Harbor (CHTS1): 82.9 degrees.
Capers Nearshore Buoy (Station 41029): 81.7 degrees.
Fripps Nearshore Buoy (Station 41033): 82.8 degrees.