As it is just about every year, this year's field is fast and deep, with a few standouts.
Always a major factor is the weather. At the 5am start it will be about 53 degrees in Squaw Valley and Auburn will peak at 102 degrees around 5-6pm on Saturday. The first man will arrive in Auburn around 8pm when it will still be over 90 degrees. This is a hot year but not insane unless the forecast changes. There is apparently little or no snow on the course this year which should make the race a little more predictable than last year.
On the women's side, my prediction is that Courtney Dauwalter wins by over 30 minutes, in around 18:20. Not very bold but she is a first-timer at Western States and we have many past-champs racing, most notably Stephanie Violett and Kaci Lickteig. Steph seems ready to go while Kaci seems not not be back to her full strength after battling some injuries.
On the men's side there seem to be more potential winners although none have won Western States before. Jim Walmsley on paper is the favorite, having gone 93 miles on course record pace in 2016 before a wrong turn turned into a long walk home in ~18hrs. He raced his way into the 2017 race hoping to smash it, but failed to adjust for conditions and crumbled early before dropping out. Francois D'Haene may be king of the mountains right now, but WS100 isn't really a mountain race. Hopefully we will see him in the top 5 at least by halfway. Jared Hazen looks to improve on this 3rd place finish from 2015 (he was 20 years old). He probably couldn't beat Jim if they both have their best days, but it wouldn't be a surprise at all if we see Jared in the lead after mile 78. I see his race playing out much like Ryan Sandes' who let Jim take off before rolling him up in the last 40 miles. Two other men to watch (in my opinion) are Tim Freriks and Kris Brown. Both are relatively new to the ultra scene and placed 1st and 4th at the 2017 TNF 50 miler when most people heard Kris Brown's name for the first time. He seems like he has a good head and probably will be nowhere near the leader at mile 30 or even mile 50.
Personally, I'll be out on the course spectating this year. The plan is to hike up the Escarpment (mile 3) just before the start to watch the sea of headlamps crawl up the first climb.