The German weather service DWD is not
always the fastes one updating his informations, but he supplies detailed weather information across the whole European Alps with all regions. You will also find forecasts over several days, that are
very accurate and alow a first detailed motorbike tour planning.
They have not yet fully translated all
pages in English language and you won’t find all relevant information in the English language section. So choose the German one and go through Google translation.
Most information can be pulled out of
the satellite pictures and Isobaric maps and allows at least a first tour planning across Europe.