There are options for skiing closer than Mammoth (2.5 to 3 hours depending on traffic), however coming from the Rockies they will likely be less than awe inspiring.
Your best bet to get challenged would probably be Mt. Baldy http://www.mtbaldy.com/
but they rely heavily on natural snow fall and so far this year it is not looking good.
Other options that dont rely so much on natural snow fall would be:
Snow Summit/Big Bearhttp://www.bigbearmountainresorts.com/index_winter.php
The smallest, Trinity Mountain http://www.trinitymountainresort.com/
was destroyed in the recent fires, so it's out.
I am sure some of the other local Bears will chime in, so dont hesitate to ask for more info if you need it.
Hope everyone is having a good day.