what would be a good reason for a party to travel to neverwinter via phandalin(they only stop in phandalin due to a storm) one party member nees to have some sort of quest to neverwinter the others(dm pcs) will arrive and form a fellowship with him 

They may not arrive in neverwinter so it needs to be something that if the story derails away from neverwinter it has no real conequence but rather adds flavour to a chance encounter

I'm going with neverwinter since it's a city that's well known along the sword coast

I could do with seperate ideas to fit a fighter, rouge,wizard and cleric

Have you read the adventure hooks to lost mines of phandelver? That could help, as for other ideas, maybe the cleric needs to go on a pilgrimage, (though phandalin would be a strange place for that), a wizard could be going to investigate rumors about the lost mines, which could help plot wise, then, rogue and fighter could just be going there to chase some goblins that wronged them, or even the whole group. Here are just a few ideas, but have fun

Will give that a read