Lappi claimed three stage wins from the four afternoon tests that were plagued by snow flurries that made conditions incredibly challenging for crews. The performance helped Lappi overhaul Katsuta to open up a 3.2s rally lead after eight of 18 stages.
Katsuta ended the day as the lead Toyota after overnight leader Kalle Rovanpera crashed out on stage four after running wide into a snowbank, with Hyundai’s Ott Tanak retiring after also falling victim to the snowbanks.
WRC2 leader Oliver Solberg made the most of cleaner road conditions to end the day in an incredible third overall (+1m20.7s), driving a Toksport Skoda Fabia.
"Third place in a WRC2 car is incredible and here on my home rally there is such a spectacular atmosphere. It's a bit of a dream and I'm very happy," said Solberg.
M-Sport’s Adrien Fourmaux rounded out an impressive day in fourth, 5.6s behind Solberg, while Elfyn Evans was fifth (+1m50.0s). Championship leader Thierry Neuville headed to the end of day service with a fuel pressure problem in eighth, trailing Rally2 drivers Sami Pajari and Lauri Joona.
Heavy snow made conditions incredibly tricky for the crews as the afternoon loop began. Such was the significance of the snow fall, the stages fell into the hands of the slower Rally2 cars that were lower down the road order and faced a much cleaner road surface.
The top five fastest times posted on stage five, the second pass through #42 Brattby, belonged to Rally2 drivers.
Georg Linnamae emerged from the blizzard with a benchmark time to score a first stage win for the new Toyota GR Yaris Rally2 car.
The Estonian was 2.4s faster than WRC2 leader Oliver Solberg and class rivals Mikko Heikkila, Lauri Joona and Fabrizio Zaldivar.
Lappi was the quickest Rally1 entrant with the sixth fastest as he closed to within 5.3s of rally leader Katsuta, who could only post the 11th quickest effort.
"Grip is nothing. Studs don’t work at all. As you can see, there is more than 10cm of snow in some sections. No chance to find the grip, just using the banks and lines. Sometimes you hope there is bank, it’s proper bobsleigh at times,” said Katsuta.
Fourmaux was 21st, Evans, who declared the test “undriveable” was 24th, while Neuville ended up 26th on the leaderboard.
The drama continued into stage six [Norrby 2, 12.36km] as Neuville struggled to fire up his i20 N before the stage start. He checked into the stage four minutes late, incurring a 40s penalty.
The Belgian did however receive the advantage of falling behind Evans on the road order leaving the Welshman to face the worst of the conditions.
Neuville’s run through the stage wasn’t plain sailing. The bonnet on his car wasn’t attached properly following the work Neuville and co-driver Martijn Wydaeghe carried out on the car before the stage.
As a result, a bonnet pin failed, resulting in part of the bonnet lifted up during the stage.
Neuville also survived a lucky scare with a snowbank but was able to clock a time 3.7s faster than Evans.
At the stage end Evans suggested that Neuville’s issue at the start of the test may have been a tactical move.
“I guess the spirit of competition has gone out of the window. Let’s wait to cast judgement on that before we say something we regret,” said Evans.
“Suddenly we had an issue with the engine it was not running and something went on at refuel before and we had to check it but obviously the bonnet was not shut properly,” explained Neuville.
When it was suggested that Evans thought it was a tactical move, Neuville, added: "I don't know why [he would think that]. He was at the refuel earlier when our car didn't fire up so he should know."
Lappi claimed the stage win to bolster his victory hopes by taking 5.0s out of rally leader Katsuta to reduce the overall margin to 0.3s.
Fourmaux managed to climb above Evans into third overall as the Frenchman’s measured approach continued to pay dividends, while Evans faced the disadvantage of opening the road.
The snowy conditions intensified further reducing the visibility for drivers in stage seven, the penultimate stage of the day held in darkness.
Lappi labelled the condition “crazy” but somehow managed to come through the test with another stage win.
A time 2.1s faster than Katsuta helped the Finn overhaul the Japanese into a 1.8s rally lead.
“You can’t use all the extra lights so you have to go with a low beam and when you’re driving over 160kph it’s a bit crazy when you can’t see far. But you have to trust the notes,” said Lappi.
Solberg benefitted from a much cleaner road surface to incredibly leap from fifth overall to third.
Neuville, sitting 11th on the rally leaderboard, was sixth fastest behind Heikkila and Pajari, but the Belgian again took more time out of Evans, who dropped to sixth overall.
Lappi completed a hat-trick of stage wins by winning stage eight [Umea Sprint, 5.16km] by 1.4s from Katsuta, while Neuville ended the day showing signs of pace to post the third fastest time.
Rally Sweden continues on Saturday with the field set to tackle seven more stages.
