The third-placed Baggies visit second-placed Fulham at Craven Cottage knowing a win would see them leapfrog their promotional rivals in the standings.
And with Molumby having enjoyed the support from the stands in home wins over Blues and Bristol City, he is thrilled that Albion will be roared on by a sold-out away end.
Asked how big a part the fans can play tomorrow, the midfielder said: "Massive. Our home form the last few now has been quite good and the supporters are massive to that with the atmosphere.
"I think it's important us as players and as a team we make The Hawthorns a difficult place to come. We've done that the last few games, so to have them coming all the way down and packing out the away end will be brilliant and definitely help us."
The 22-year-old Irishman joined on loan from Brighton & Hove Albion in the summer, living with international team-mate Dara O'Shea for several weeks.
"I've been really enjoying it," said Molumby, reflecting on life at Albion so far.
"I think day in, day out I've just been trying to come in with a smile on my face and just enjoy it.
"That's probably the key to it – I'm back enjoying my football, I'm enjoying being around the lads and everyone has helped me settle in quite well.
"It helps when you are winning games and doing well, so I've just been really enjoying it."
On living with O'Shea, Molumby added: "I've known Dara five or six years now and he's been brilliant with me. I was living with him a good six weeks or so – him and his partner – so for him to take me in and make me feel comfortable was unbelievable.
"I was really grateful for that and he's done a lot since I've been here to make me feel at home."
Molumby was also familiar with another Irish international in Callum Robinson, as well as former Brighton players Matt Clarke and David Button, making transition to life in the Midlands that little easier.
"You can lean towards a few of the boys and obviously it helps when you've been in teams with them or you know the lads coming in," he said. "Robbo, Dara, Clarkey I know – Butts as well – so there was a good little group there I knew before coming in, so it definitely helped."
Despite settling in well, Molumby did have to be patient for his chance initially – though he has now made five appearances, starting the last two.
"I think I've done OK," he said. "Obviously there's stuff I need to do better.
"It probably helped having a bit of time working day in, day out with the gaffer on how he wants to play, and I feel the more I play and the more I get used to him the better I can get hopefully.
"It's been brilliant to get in and to get the win the other day against Bristol was brilliant."
With Jake Livermore and Alex Mowatt ruled out, it was in that 3-0 win over Bristol City that Molumby was partnered with Robert Snodgrass in the middle of the pitch – and it was an experience he enjoyed.
"It was very good playing with Snods," he added. "I'm quite close with him off the pitch as well – he is another one who has helped me settle in really well and I've been spending a bit of time with him outside of the football pitch as well. He's been brilliant.
"And us two, because the skip and Al (Mowatt) have done so well, it was about us being patient and waiting for our chance."
So just how important is it to carry on that form and beat Fulham at Craven Cottage tomorrow?
"I know it's early in the season still, but we definitely want to beat the teams ahead of us in the table at the moment and really put down a marker to the rest of the league," added Molumby.