Im planning a snowboard trip up to Big Bear Mountian next month and I'm looking for any tips on flying in higher altitudes, I usually fly under 1000' Elevation. It will also be my first time flying in colder conditions arouns 30°F.  
Any tips / thoughts are appericiated.

I recently flew at 10,000 feet up to an altitude of 11,000 with my Phantom 4.  I was at the summit of Mount Agung.  The first thing you notice is a different sound from the motors, definitely sound much louder and working harder to maintain lift.  However, my Phantom 4 performed flawlessly at that altitude.  My only advice is that you definitely have to hand launch and catch due to wind and terrain issues.  Not a problem for me and a Phantom, but, may be trickier for you with a Mavic.