I think you are in the wrong section since it's a question and not a order but I can't move the topic anyway. SO...

It's not rreally possible to have clouds all the time since the water that forms them have to fall eventually. But they will reform. If it's located between the tropics, there will be more evaporation, so more clouds but no snow. If it's in a low pressure zone, it's more likely that the winds will come toward the valley, bringing moisture or dry air dependig on surronding. But even with the perfect conditions, it's not possible to have a perfect cover. So my best solution would be a tropical climate with lot of humidity high temperature, maybe like the Amazon but more extreme, if it's possible.

For more info you can check here : The Climate Cookbook