By Julian Linden

DALLAS (Reuters) - A rare snow storm deep in the heart of Texas has added another unusual twist to Sunday's Super Bowl between the Pittsburgh Steelers and the Green Bay Packers.

The game was already looming as a classic battle between two of the NFL's most successful and popular franchises but the big freeze that has paralyzed large parts of the United States has added a surreal touch to the occasion.

The host city of Dallas has been transformed into an unlikely winter wonderland as the teams put the finishing touches to their preparations for the biggest annual sporting event in North America.

More than 100,000 people will cram into the space-age Cowboys Stadium to watch the game live while an estimated worldwide audience of more than 160 million are expected to watch the extravaganza unfold on television.

"When you look at this matchup, you say Pittsburgh Steelers and Green Bay Packers - that's football," NFL commissioner Roger Goodell said on Friday. "These two great organizations, who have had so much success in the past, they represent the traditions of our game."

The Steelers and the Packers showed their pedigree when it mattered most to reach the Super Bowl after a wildly fluctuating season where nothing really went according to the script.

"Fortunately for us, we have what you can't buy," Pittsburgh coach Mike Tomlin said. "(We have)...an unbelievable standard and expectation and all those great things."

After securing one of the NFC wildcards after finishing second in their division, they won three sudden-death playoffs on the road.

"Chasing perfection and catching excellence on the way is something I think exemplifies everything that every football team, particularly ours, is trying to accomplish," Packers coach Mike McCarthy said.

The Packers are slight favorites to win but few people are exactly sure what to expect. Both teams have outstanding quarterbacks, bruising defenses and can pile on the points.


This is the first time the teams have met in the playoffs and the Packers have not beaten the Steelers in the regular season since 1995, although they have only played each other three times since then.

At their last meeting, in 2009, the Steelers won 37-36 with Pittsburgh quarterback Ben Roethlisberger throwing a touchdown on the final play, but McCarthy is expecting a lower-scoring game this time.

"I know first hand that our defense has improved and so has theirs," he said.

The Steelers and Packers boast the two best defenses in the NFL this season but, as always, the battle between the two quarterbacks is looming as one of the keys to the outcome.

Aaron Rodgers, appearing in his first Super Bowl after taking over the reins in Green Bay from Brett Favre, has been in great form this season and shown no signs of stage fright as he approaches the biggest test of his career on the biggest stage in American sport.

"That is what is so exciting for this country and the world to look at this game and think, 'wow, that's real football'" said Goodell.

"This is fun, this is celebrating the game that I love and we all love and I think it is going to be a terrific night."

(Editing by Frank Pingue)