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PHOENIX — A dust storm up to 50 miles wide and a mile high descended on the Phoenix area on Tuesday night, grounding flights, forcing drivers to stop and causing thousands of power outages.

Towering over skyscrapers and grounding flights, the wall of dust swept across the desert from the south at around nightfall, blanketing downtown Phoenix.

The National Weather Service said strong winds with gusts of more than 60 miles per hour  moved the dust cloud northwest through Phoenix and the cities of Avondale, Tempe and Scottsdale.

More than a dozen communities in the area also were placed under a severe thunderstorm watch.

Hundreds seek help
Phoenix's fire department received 720 emergency phone calls during the dust storm and fire crews handled over 320 incidents during the same time period, NBC News reported.

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The dust cloud had originated in an afternoon storm in the Tucson area before moving north across the desert, said National Weather Service meteorologist Paul Iniguez.

He said that before bearing down on the Phoenix valley, radar data showed the storm's wall of dust had reached as high as 8,000 to 10,000 feet (nearly two miles).

Once it neared the valley, the cloud had fallen to some 5,000 feet (just under a mile), according to the weather service.

"This was pretty significant," Iniguez said. "We heard from a lot of people who lived here for a number of storms and this was the worst they'd seen."

The strong winds toppled trees and some 8,000 Salt River Project utility customers were left without power, KNXV-TV reported late Tuesday.

The Arizona Republic reported winds also downed live wires in Tempe that sparked a fire at a busy intersection. Firefighters later extinguished the blaze.

'Grit in your teeth'
A woman in Phoenix, who had parked in a lot to escape the storm, told TV station KTVK, in a video posted on its website Azfamily.com, that she had never seen a storm like it in the 20 years she has lived in the area.

"The grit in your teeth right now ... I just hear crunching," she added. "It is amazing (the storm). It's the most amazing thing I have ever felt in my life."

Joshua Lott  /  Reuters

Motorists drive along 16th Street in Phoeniz, Ariz., during a dust storm on Tuesday.

The Federal Aviation Administration said on its website that because of low visibility in the area, no Phoenix-bound flights were allowed to leave Las Vegas or Los Angeles airports until 9 p.m. PT Tuesday (12 a.m. ET Wednesday).

Flights at Phoenix's Sky Harbor International airport were also grounded for about 45 minutes until about 8:55 p.m. PT, NBC News said.

A Sky Harbor spokesperson told NBC News that no Sky Harbor flights needed to be diverted to other airports.

One flight that was supposed to fly into the smaller Mesa Gateway airport was diverted to Phoenix.

The spokesperson said that conditions outside appeared to be back to normal, with much of the dust settled.

The storm was part of the Arizona monsoon season, which typically starts in mid-June and lasts through Sept. 30.

NBC News, msnbc.com staff and The Associated Press contributed to this report.