7:05 p.m. update: A moderate storm cell has developed about 10 miles east of the Overton arm of Lake Mead, and is slowly moving west. It could bring rain to Lake Mead in the evening hours. Other storms east of Kingman, Ariz., appear stationary with little movement. They could be causing flooding in the mountains and valleys east of Kingman.
6:30 p.m. update: A few small storm cells have popped up to the west of St. George, Utah.
5:55 p.m. update: The line of storms east of Kingman, Ariz., continues to move gradually southwest, away from the Las Vegas Valley. There are spotty showers over central Nevada, more than 200 miles from Las Vegas. Current radar indicates no rain threat to Las Vegas for the next several hours although the flash flood watch remains in effect.
5:15 p.m. update: There are three light and small cells on the south side of the Mt. Charleston peak. To the southeast, a moderate line of storms is approaching Kingman, Ariz., from the east.
4:45 p.m. update: The closest rain to Las Vegas was a moderate rain cell over Nelson and Peach Springs about 70 miles southeast of the valley.
LAS VEGAS (KSNV MyNews3.com) -- The flash flood watch for must of the desert southwest continues through Sunday evening.
The National Weather Service issued the watch Friday afternoon for a period from noon Saturday to 10 p.m. Sunday.
As of 2:35 p.m., skies were mostly overcast in the Las Vegas Valley. Some light rain was falling along Interstate 40 in California west of its junction with Interstate 15 and east toward Flagstaff, Ariz.
In re-issuing the flood watch advisory at 12:26 p.m. today, the NWS said thunderstorms with heavy rain will expand in coverage this afternoon through Sunday evening leading to an increased threat of flash flooding across most of the region.
Affected areas include all of Southern Nevada, much of northern Arizona and large portions of southeast California.
Residents should be aware of rain clouds, thunderstorms, lightning and high winds that could pose threats to life and property.
The NWS said a substantial increase in moisture will accompany a low pressure system moving north from Baja California and northwest Mexico today through Sunday evening.
The storm system may trigger widespread rain and flash flooding.