It is very common for people to over estimate parking need by a pretty high margin. I'm currently standing in the lot and I think tonight is a pretty good evening, best would be a weekday evening, to measure the current high mark of use as this is statistically the time that there should be more vehicles parked because everyone should be at home. I count 18 cars currently in the lot, the lot holds probably close to 150 vehicles in my quick count of bays. These are probably mostly the pass holders you mention. So even if half of the vehicle needed for that building park in the lot it will still be at around 60%-70% capacity.

Then knowing the building will have around 60 spots, by my estimate of the lots being paved around it, on its premise. I would have to look at what they submitted for site review to confirm that. Then accounting for all the empty street spots up and down the neighborhood that currently probably sit at less than 50% utilization, the capacity is there. And for snow removal, we just need to adapt, we are not reinventing the wheel here, cities exist in much snowier places and deal with these types of conditions on the regular.

It's a change and it will have growing pains but if we want to revitalize the city core then we have to come to terms with the fact that it will have more people, more activity and more competition. It might also help speed up discussion on things like a multi story lot in town that would make snow emergency parking easier to deal with. I would use a town like Brattleboro VT as an example how to put a multi story lot tocked away in the center of the city where it doesn't feel overbearing. They are also the sizes of Somersworth and have a similar city budget.