The 27-year old former world overall champion charged down course in a time of one minute, 51.36 seconds, finishing ahead of France’s Marie Marchand-Arvier (1:51.46) while Lindsey Vonn of the US placed third in 1:51.82.
Canada’s Emily Brydon was fourth and Austrian Martina Schild rounded out the top five.
“I had some turns where I really hit the spot and went aggressive,” Pärson said.
Pärson reached the podium for the first time in Lake Louise two years ago with a third place in the downhill.
She used to profess a dislike for the Lake Louise course but now admits her earlier problems in the Canadian Rockies stemmed from a lack of off-season speed training.
“I have to find something better tomorrow because I don’t think other girls are going to let me win,” Pärson said.
“The conditions this year are better for me. The course is a little softer and smoother on the surface so I can be aggressive in my tuck. This is the best in all the years I been here.”
Pärson is stalking reigning overall World Cup champion Vonn and hoping to rack up numerous World Cup points in the two downhills and super-G race this weekend.
Pre-race favourite Vonn was fastest in the first training run and place third on Thursday.
Pärson likes the role of being the underdog.
“It is easier to be the hunter,” Pärson said. “So I hope this year we hunt well.”
For the second day in a row Vonn stood up before the finish line. The 24-year-old American says she wanted to leave something in the tank for Friday’s season-opening downhill.
“I don’t want to try too hard in the training runs,” Vonn said.
“With the bad light I was a little nervous and I knew it was a lot faster today so I just tried to be in a solid position.
“I don’t like to do that well in last training run. I feel like I can give more on race day. I never want to feel like I have it. I got to always keep working.”
Once again most of the skiers wore protective tape on their faces Thursday to shield themselves from bitter cold that reached minus 20 degrees Celsius.
France’s Marchand-Arvier had a friend draw a skull and crossbones on her right cheek to give her inspiration going into Thursday’s training run.
“It was not my first intention (drawing) but I was good today,” said Marchand-Arvier who finished second. “Maybe I will use it again tomorrow.”
Marchand-Arvier was pleased she was able to accomplish what she set out to do.
“Last year I didn’t ski fast here had lot of problem in my training so this year I tried to be very fast in the training so that I can have the same feeling on race day,” Marchand-Arvier said.
“This takes some of the pressure off. If I am good in training then I usually am good in the race.”