Rain is here. How much will we get, and how long will it last?

Joy McKay steps out into the rain Friday in downtown Rock Hill.
Joy McKay steps out into the rain Friday in downtown Rock Hill. tkimball@heraldonline.com

After nearly four weeks without significant rainfall, the Rock Hill area is poised to get wet this weekend. It might get very wet.

Forecasters say a slow-moving low pressure system will bring waves of showers and thunderstorms to the Carolinas, dumping enough rain to douse the parched gardens, flower beds and lawns. At first, the rainfall is not expected to cause problems. But by later in the weekend, that could change.

“With multiple days of moderate to heavy rainfall, the threat of flash flooding could increase,” says National Weather Service meteorologist Sandy Lacorte.

The last measurable rain reported at the airport in Rock Hill was .01 of an inch on May 20. Before that, you have to go back to Mothers Day weekend, when more than 1 inch fell May 11, and .05 of an inch the next day.

The U.S. Department of Agriculture’s weekly Drought Monitor shows drought conditions have increased across South Carolina, although York, Chester and Lancaster counties are not yet considered to be in drought. The National Weather Service had showers and thunderstorms in the forecast Wednesday and Thursday, but little or nothing fell across much of the Rock Hill area.

That changed Friday.

Showers and thunderstorms that are forecast to spread across the area Friday will continue Saturday, Sunday and Monday. Lacorte said pinpointing rainfall amounts is tricky, since a variety of factors will be in play. But this is expected to be a multi-day event.

“The unsettled weather pattern will continue well through early next week,” Lacorte said.

The official forecast calls for shower and thunderstorm chances to decrease Tuesday and Wednesday, but Lacorte said some of the computer guidance indicates the threat of rain could continue late into the week.

Steve Lyttle on Twitter: @slyttle