Strong winds caused power outages affecting thousands of customers, toppled trees that blocked major traffic arteries, and blew off portions of more than a dozen roofs on Oahu.

Hawaii Volcanoes National Park on the Big Island — with winds gusting to more than 50 mph — shut down several popular sections.

The winds were expected to continue this morning and afternoon as they have for the past few days, with sustained speeds of 20 to 30 mph and gusts up to 50 mph, National Weather Service forecaster Matthew Foster said.

Foster said the strong tradewinds were expected to back down by tonight as a high-pressure area to the north becomes weaker.

But he said the winds would be increasing again over the weekend as a new high-pressure area moves close to the islands.

Hawaiian Electric Co. spokesman Darren Pai said wind-swung power lines caused short-circuit outages for 2,000 customers in Manoa from about 11:15 a.m. to 2 p.m. yesterday.

The outage included Mid-Pacific Institute, and when the power came back on, an apparent surge started a fire in the air-conditioning unit at Bakken Auditorium, Chief Financial Officer Pat Garvey said.

The school called the Honolulu Fire Department at 3:20 p.m. when a maintenance man smelled smoke, but firefighters could not determine the source.

No flames were visible. The school will have mechanical experts investigate the air-conditioning system to determine the cause.

Pai said a similar wind-caused outage occurred for 1,000 customers in the Moanalua-Salt Lake area from about 11:30 a.m. to 1 p.m. and 800 customers in Kalihi around 4 p.m.

Power was restored to two-thirds of the Kalihi customers by about 6 p.m.

Firefighters were called to Chuck's Corvette Clinic at Kamani Street in Honolulu when a cover to a vent broke and was dangling precariously on the top of its roof.

“;I was afraid it would come off and kill someone,”; said business owner Chuck Garner. “;It's been gusting pretty good.”;

Garner said he was eating lunch when there was a loud sound.

“;I thought something was coming through the roof,”; he said.

High winds also blew off parts of an air-conditioning enclosure at the top of Foodland at Beretania Street at 2:50 a.m. yesterday.

Wind-downed trees on Pali Highway at Waokanaka Street blocked one lane of Kailua-bound traffic at 12:15 p.m. for more than 20 minutes and two lanes of Kaneohe-bound traffic on Likelike Highway at 1:12 p.m. for close to 20 minutes.

High winds prompted county officials on the Big Island to shut down trash services at the Waimea Transfer Station at 9:30 a.m.

A couple of pieces of garage roofing blew off the building at the county baseyard in Waimea, county spokesman Hunter Bishop said.

“;Power has been going off and on for most of the day in Waimea,”; Bishop said.

Bishop said the closure of the Waimea Transfer Station was to ensure public and employee safety.

The transfer station was scheduled to reopen today if weather conditions improve.

Big Island residents in Waimea experienced periodic power outages throughout the day, and rangers at Volcanoes National Park shut down Mauna Loa road and trail, the backcountry, cabins at the summit and Red Hill, and the Namakanipaio campground, said park ranger Mardie Lane.

“;What we're doing is working to prevent any injuries,”; Lane said.