yes you can get up to 100 miles a week before outdoor. simply run 14.285714285714285714285714285714 each day.
It takes one week to get up to 100. Just go out and do it. If you're running 60 now, you can run 100 - the limiting factor will be your lack of fitness. But that's the whole goddamn reason you're running for in the first place, isn't?
When I was in high school I used to go out and see what I could do. I'd hit 130 one week in the summer, then the next year I hit 150, which gave me the confidence when I started regularly hitting 100-110. Then again everyone just went out and got the job done. I'll admit, those were the days that Runner's World was actually the source for information about running, and we didn't have internet "experts" destroying the sport.
Part of the problem with you guys is that you look at all weeks as being the same, they're not. You also look at mileage - whether it's high or low as the end-all - IT'S NOT. There is base mileage, there is in-competition mileage, there is in-competition important race mileage. There is travel week mileage, there is rest week mileage.
You just don't go out and run, week after week at 100 (or whatever arbitrary number you've chosen). You work your mileage around your current schedule, your current goals, and your long-term plan. Some weeks are high, some are low - all depending.
The reason why most of you don't "get it" is you've been trained to believe in the superstitious bullshit throw at you by the self-proclaimed "experts" who've never run competitively before. You subscribe to the idea of writing and executing contrived training plans, which, as a generalization, are nothing more than exercises in numerology. How does a piece of paper written in advance account for extemporaneous adjustments? It doesn't.
I wish you guys would spend more time actually putting in the miles rather than pontificating about way to re-arrange the miles. You'd see results.