Tropical Storm Priscilla could bring heavy rain and a “significant” risk of flash flooding to the southwestern United States through this weekend, forecasters warn.

Flash flooding is a growing risk in the southwestern U.S. through this weekend. The reason is a tropical storm headed inland from the Pacific Ocean.

Hurricane Priscilla was beginning to lose some punch but was still a powerful Category 2 storm off Mexico's Pacific coast, the Miami-based National Hurricane Center says.

The NWS has been tracking the surge of moisture from Priscilla as it shifts northward. On Thursday, the NWS Weather Prediction Center warned that Phoenix and Winslow, Arizona, faced a moderate risk of flash flooding, in which there was at least a 40 percent chance of flash flooding.

Priscilla could bring flash flooding through the weekend across the U.S. Southwest, the U.S. National Hurricane Center in Miami said. Jerry was centered about 355 miles east-southeast of the northern Leeward Islands and moving west-northwest at 20 mph with maximum sustained winds of 65 mph, the center said.

The National Weather Service is warning that Tropical Storm Priscilla may deliver light rainall and thunderstorms across Southern California in the coming days.

Priscilla could bring flash flooding through the weekend across the U.S. Southwest, the U.S. National Hurricane Center in Miami said.

The end of the week could feel different, with remnants of Priscilla poised to bring rain, wind and humidity to San Diego County.

As concerns of potential flash flooding loom from Tropical Storm Priscilla, Tucson residents are flocking to sandbag stations to prepare for the worst.

Farther out in the Pacific, Tropical Storm Octave was weakening about 660 miles (1,065 kilometers) southwest of the southern tip of Baja California. Its maximum sustained winds were 40 mph (65 kph) and it was moving east at 12 mph (19 kph). Octave, which wasn’t threatening land, was expected to dissipate by Thursday, forecasters said.

Moisture from the remnants of a tropical system is moving through Colorado today, leading to periods of heavy rain across the western third of the state, and shower chances in southern Colorado.