James Curtis shovels out his car in front of Sechrist Hall on the campus of Northern Arizona University in Flagstaff, Ariz. on Thursday, January 21, 2010. Heavy storms continue to blanket the area and have caused the closure of all of the schools in the Flagstaff area through the end of the week.

A major winter storm slammed into Southern Arizona on Thursday, bringing hurricane-strength wind gusts, rain, a rare tornado possibility and heavy snowfall in the mountains.

The bad weather was expected to continue into the weekend as another storm system comes through tonight, bringing rain, snow and lower temperatures.

Snow accumulations were expected to drop to about 3,500 feet by early Saturday. Much of Tucson sits at about 2,500 feet. Mount Lemmon could see up to 2 feet of snow before the storms pass. It should start clearing by Sunday.

The storm, which is affecting most of the state, snapped power poles, stranded hikers, uprooted trees in the city and caused a late-night fire on Tucson's northwest side. Dust-related crashes on Interstate 10 snarled traffic between Tucson and Phoenix for much of the day.

A rare tornado watch was in effect for several hours for Southern and Central Arizona Thursday evening, including Pima County. The watch was extended in Pinal County until early this morning.

Craig Shoemaker, a National Weather Service meteorologist, said this was the first time he could recall the Tucson weather office issuing a tornado watch. "I'm pretty sure it's the only time," Shoemaker said.

The storm brought everything to Tucson that one would expect from a winter storm system, including heavy rain. Up to an inch of rain was expected in Tucson by this morning, according to the weather service.

Blizzard conditions were likely to exist above 7,000 feet in Southern Arizona through mid-day today. High winds and rain were expected to continue throughout today and into Saturday.

The wind gusts reached 86 mph Thursday night in Summerhaven, Shoemaker said. Ajo, west of Tucson, reported the highest wind gust in the region at 94 mph, he said.

In addition to causing traffic delays and power outages, the storm also prompted some airlines to cancel their flights in and out of Tucson International Airport.

Southwest, US Airways, Mesa, United and Air Canada airlines canceled one or more flights Thursday at Tucson International, particularly flights with Denver, Southern California or Phoenix connections. More in Business, A7.

The storm wreaked chaos in other ways across Tucson and Southern Arizona:

• Sixteen people were rescued Thursday afternoon after they were stranded along a trail in the Sabino Canyon Recreation Area by floodwaters caused by heavy rain and snow in the Catalina Mountains, authorities said.

The stranded visitors were walking and hiking along the Bear Canyon Trail, which leads to Seven Falls, when the water in wash they'd previously passed became too high to cross back over, said Heidi Schewel, a spokeswoman for the Coronado National Forest.

Authorities guided the group off the trail by using an alternate route, said sheriff's Deputy Dawn Barkman, a Pima County sheriff's spokeswoman.

The recreation area is likely to get more floodwaters from the storms. It usually takes 24 hours for the waters to come down from the mountains to the lower elevations, she said.

People are advised to use caution in the area, she said.

• The storm caused power outages on Mount Lemmon, leaving about 200 customers without power, said Romi Carrell Wittman, a Trico Electric Cooperative spokeswoman.

The outages were caused by trees that fell on the company's power lines, Wittman said.

She did not know when the customers would have electricity, she said.

The highway up to Mount Lemmon was closed Thursday to all traffic. County road conditions can be checked by calling 547-7510.

The Northwest Fire/Rescue District received at least four calls for downed power lines during the afternoon, said Capt. Adam Goldberg, a district spokesman. No injuries were reported, he said.

The district also responded to a mobile-home fire late Thursday that displaced a family of five, he said.

The blaze began at the home in the 5500 block of North Shannon Road after electrical lines fell from a broken power pole, he said.

Six houses on the property were evacuated after strong winds knocked over the pole and electrical lines, Goldberg said.

The fire burned the attic and caused smoke damage to the inside of the house, Goldberg said.

There were no reported injuries.

The residents of the other five houses were able to return to their homes, but they did not have electricity, he said.

There was no timeline for when power would be restored.

The displaced family was going to stay with relatives until repairs could be made on their home, he said.

On the east side, a tree fell into a house in the 9500 block of East Harrison Circle, said Capt. Trish Tracy, a Tucson Fire Department spokeswoman.

No injuries were reported in that incident, Tracy said.

• The wind caused major damage on the Tohono O'odham Nation.

Red Cross officials responded to the Hickiwan district of the nation, near Ajo, to set up shelter and provide food for at least 10 people who were displaced during the storm, said Red Cross spokesman Mike Sagara.

The roofs of four homes were damaged by heavy winds, forcing people to seek shelter at the district's recreation center, said Tohono O'odham spokesman Matt Smith.

Later in the evening, a massive power outage knocked out electricity to almost 15,000 customers on the nation. A second shelter was being set up late Thursday.

The outage occurred after the wind knocked down a power pole that was carrying the main electrical line, Smith said.

Arizona Public Service crews were working on the outage Thursday night, but officials did not know when power would be restored, he said.

All schools on the reservation, including the nation's community college, will be closed today.

• On Interstate 10, high winds and dust limited visibility and backed up traffic for drivers traveling the interstate between Tucson and Phoenix during the afternoon.

A dust storm caused zero visibility on I-10 in Casa Grande, and 40 mph winds whipped up more dust near Eloy, the Department of Public Safety said.

A tractor-trailer rig rolled onto its side during the windstorm on the interstate near Picacho, blocking the westbound lanes.

Two local events in Tucson were canceled this weekend because of the rainy weather.

• Organizers delayed the highly anticipated launch of the Farmers' Market at Udall Park by a week because of the storm.

Instead of starting today, the market will launch Jan. 29. It will start with a pilot period, running every week from 9 a.m. to 1 p.m. at Morris K. Udall Regional Center, 7200 E. Tanque Verde Road.

• Rillito Park Racetrack is holding its horses this weekend.

Rain has rendered the track unsafe for racing this weekend, general manager Pat White said.

Racing will return Jan. 30. Gates will open at 11 a.m. and post time is 1 p.m..

Many other areas of the state were hit just as hard as Southern Arizona, or harder:

In Phoenix, rain fell steadily since early Thursday, leaving pools of standing water in the streets and intersections flooded.

All flights into and out of Phoenix Sky Harbor International Airport were expected to stop by Thursday afternoon because of high winds and low visibility.

Six to 7 inches of rain was forecast for northern Maricopa and Gila counties. The National Weather Service said the storm would bring about 4 inches of rain to Phoenix - more than half of the rain Phoenix typically sees in a year.

• In Flagstaff, residents dug out from 3 feet of fresh snow Thursday and braced for another 2 feet of powder.

The snow wreaked havoc on Northern Arizona highways, forcing authorities to restrict travel on some roads and shut down other roads completely.

Portions of Interstates 40 and 17 near Flagstaff were closed by Thursday evening. It wasn't clear when the state would reopen the highways.

"If you don't have to travel, don't," said Lt. Steve Harrison of the Department of Public Safety. "That's the biggest thing we're trying to tell people, especially in Northern Arizona."

Authorities in Sedona were asking residents in low-lying areas near Oak Creek to voluntarily evacuate and others to be prepared to leave on a moment's notice.

Forecasters said the creek would crest at nearly 20 feet early today, potentially sending 2 to 4 feet of water through local businesses and mobile homes downstream.

A tornado near the California-Arizona state line toppled big-rigs and downed high-voltage power poles atop a car with a person inside late Thursday.

Officials said he was later rescued but his condition was unknown.

The Associated Press contributed to this story. Contact reporter Jamar Younger at 573-4115 or jyounger@azstarnet.com