Heavy snow fall favors Philly significantly without a doubt IMO.
Steady but managable snow fall I am not sure changes the odds materially.
You can definitely still have a passing game in the snow. Some QBs prefer it. Brett Farve played through it a lot in Green Bay and said it was an advantage if not too heavy, because you can still throw with snow in the air, rain is harder as it is more slippery, but the DBs can get limited by the soggy/wet field, which is a big advantage. The WRs have to make cuts too, but at least they know where they are supposed to run in advance. Defense is more reactive.
Snow heavy enough to neuter a pass game might sink us. We don't want a "snow bowl game". Our biggest advantages are QB and our offensive coach. If those things get negated because you cannot really pass the football or draw up creative plays - and on top of it Philly has the RB in the league with superior trench players, with Kyren having fumbling issues even outside of the elements - it could be curtains.
I have a good feeling about this one though as long as the snow isn't a massive dumping. It feels like everyone is looking past the Rams and giving them no shot, just because Philly rolled us last game. But this is a good team, and is much improved since the last showdown - heck, even that game likely is way different if we get up big early by KW not fumbling in the red zone. If we didn't start 1-4 due to injuries, our record would be right up there with the heavy weights, and we'd be seen way differently. Our young defence has grown over the season, particularly the secondary, from giant liability to a strength. This team is battle tested and will be playing loose. Philly hasn't faced much adversity and always seems to have noise and drama, which I think could be their undoing if they take the Rams lightly. Particularly with a home crowd that can turn on them. We're underdogs, but this game is winnable in anything but the very worst of weather conditions IMO. Karty is locked in right now and for some reason seems to kick at his best in poor weather... if it is low scoring and comes down to FG,s I am feeling good about that too.
Some forecasts are calling for 1-3 inches of snow over the course of the game. I've seen some calling for as much as 6. There seems to be variation in the models still. We'll have to wait and see. I don't think the former is going to be enough to derail us. I am not concerned about cold temperatures. Our best game of the season last year might have been the late-season OT loss in Baltimore. Our offense runs through Stafford, Puka, Kupp, and Williams. All of them have played in college or the pros in heavy snow climates (Detroit which though in a dome has division games outdoors in Chicago + Green Bay, BYU has an outdoor stadium, Washington but unsure if that is a dome or not, Notre Dame is an outdoor stadium).