As regards weather it is our experience the weather forecast service on www.storm.no have the somewhat most accurate forecast for Flåm and the surrounding area. There is also the service yr.no, as regards long term forecasts, both are just as inaccurate 🙂
Please be aware that Flåm and Aurland are amongst the driest areas on the west coast of Norway and cannot be compared with Bergen as regards amount of rainfall. However, an old Norwegian proverb says “there is no such thing as bad weather, only bad clothing”.