the NCAA tries to have regional matchups for the first round to reduce travel costs.

Between the pacific and mountain west, there are 5 teams likely to host and 4 teams in but likely not to host. The number following the team is their current RPI after today's results:

The 5 likely to host:
USC 5
UCLA 9
Stanford 13
Utah St. 17
BYU 24

The 4 likely to go on the road:
Santa Clara 43 (WCC champ)
Cal Baptist 122 (WAC champ)
Sacramento St. 245 (Big sky champ)
UC Santa Barbara 217 (Big west champ)

If you pair southern California schools, probably got UC Santa Barbara at USC and Cal Baptist at UCLA.
Then for northern California, to play at Stanford there are two choices of teams going on the road. I predict they give Stanford the easier one, so Sacramento St. at Stanford.

And that leaves Santa Clara the last one to go east to Utah to play at Utah St. or BYU. Because Utah St. is rated higher than BYU and has the head-to-head win, I guess that they bring in a worse AQ team from midwest or east somewhere to play at Utah State and give BYU the harder first round match against Santa Clara.

If BYU is hosting a first round game, that means the first round game is very winnable because BYU would be the favorite based on body of work over the season. I am not saying it would be an easy game at all, just saying it wouldn't take some big upset for BYU to win.