RENO, Nev. – A series of ever-strengthening year-end storms swept over the Sierra and across northern Nevada on Thursday, stalling traffic but giving mountain ski resorts their first new powder in a month.

The Lake Tahoe Basin was under a winter storm warning through New Year’s Day, with forecasters calling for as much as 7 feet of snow on top of the 2-3 feet that already had fallen.

The valleys around Reno and Carson City were under a heavy snow warning through noon Friday, with up to 2 feet of snow possible in the higher elevations.

A combination of heavy snow and winds gusting to 100 mph over the Sierra ridges shut down Interstate-80 and U.S. 50 overnight, halting traffic over the two principal links between Northern California and northern Nevada.

Highway 50 reopened at midmorning, with chains required, and cars with chains were crossing I-80 while truckers were chaining up on I-80 waiting for transportation officials to send their rigs on the way.

Traffic at Reno-Tahoe International Airport, snarled last month by two failures of the instrument landing system, was moving smoothly, according to spokesman Brian Kulpin.

“Flights in and out are pretty much on time with only one delay,” he said. “Our snow removal crew is on top of things, monitoring with the National Weather Service.”

He said a Federal Aviation Administration technician was on site, “baby-sitting” the ILS, which allows pilots to land in bad weather. Last month’s problems shut down the airport on two days, including the Sunday after Thanksgiving – its busiest.

The storm spread across northern Nevada on Thursday, producing heavy snow warnings all the way to the Utah line through midday Friday. An avalanche warning was posted in the Sierra for back country outside developed ski areas from Yuba Pass to Sonora Pass.

The ski resorts were delighted with the new snow, but frustrated by the winds.

“This is the most snow we’ve seen in one storm so far this season,” Alpine Meadows spokeswoman Rachael Woods said. “The powder skiing is going to be some of the most memorable conditions some of these vacationers have ever seen.”

She said the erratic winds were keeping the top of the mountain closed, but lifts were running to midmountain, where the storm had left 3 feet of snow.

Nearby Boreal Mountain Resort was running just two lifts on Thursday. Soda Springs Winter Resort didn’t even try.

“How can you complain?” Woods said. “We’re going to get so much snow out of this storm – not only for this weekend, but next weekend and months to come.”