I tend to go to Weather.com for the long range forecast, ten days and all. The OS X widget that ships with the OS appears to ping Accuweather. Its cousin on the iPhone goes to TWC. The two are frequently in conflict, and I'm not sure who to believe.
I'm going with Accuweather for now, because the optimist in me wants to believe there won't be any rain this weekend. :)
I'll give you The Weather Underground as well.
It's supposed to be relatively nice, and a warm 76 here tomorrow, but rain both Saturday and Sunday, and a check of the national radar...