RENO, Nev. — An early winter Sierra storm that dumped more than 2 feet of snow in the mountains and heavy rain in the valleys triggered power outages and school delays at Lake Tahoe and snarled traffic during the Thursday morning commute in Reno.

The upper elevations of the Sierra range north and south of Tahoe remained under a winter storm warning into Friday morning. Reno, Sparks, Carson City and much of western Nevada remained under a flood watch until 10 p.m. Thursday due to concerns primarily about swollen urban creeks.

“Periods of moderate to heavy rain will continue today as an atmospheric river system moves through the region,” the National Weather Service in Reno said Thursday. Up to another 5 inches of snow was possible in the mountains, primarily above 5,500 feet.

The Nevada Highway Patrol responded to more than a dozen accidents on slick roads in the Reno-Sparks area early Thursday. No serious injuries were reported.

The start of school in Incline Village on Tahoe’s north shore was delayed two hours due to road conditions and a power outage that left more than 13,000 customers in the dark for several hours overnight. Nearly 9,000 customers also were affected in Carson City, but NV Energy reported power had been restored to all but about 200 homes by noon Thursday.

The Mount Rose Ski Resort halfway between Reno and Tahoe had received 26 inches of snow at its summit, the National Weather Service said. Nearly 3.5 inches of rain was recorded on the California side of the lake at Tahoe City and 3 inches on the south shore at South Lake Tahoe.

Other rain totals included nearly 3.5 inches at Verdi just west of Reno, 1.7 inches in Cold Springs north of Reno, 1.3 inches in Carson City, an inch in Gardnerville and .75 inch at Reno-Tahoe International Airport.

“Significant rises on creeks and stream may lead to some minor flooding,” the weather service said.

“The primary threat … is in urban areas, clogged drainage paths, ponding of water on roads and rock slides near steep terrain,” the service said. “Recent burn scars from the past few years may also lead to an increased risk for flooding or debris flows.”