Would I need to pack any water-proof goretex jackets and pants?
I have been up there with rain for over 12 hrs. While this is not common, yes, you should take not just rain-resistant gear but rain-proof, top and bottom. Be prepared.
Add rain and wind and even at 50 F you can become hypothermic and/or dead. This was well-studied in wilderness medicine circles in the 1960s. There were studies of unprepared all-day hill-walkers in England who died in such "mild" weather.