I haven’t taken a look at the UA marathon training plan, but in general training for half marathons will look really similar to training for full marathons for people who will run a half around 2 hours or more. I have experience with other marathon and half-marathon training plans, and the main differences are the emphasis on long runs and Z3 (“tempo”) efforts.
For people running under, say, 4:30 for a full marathon, it’s important to get long runs up to at least 16-18 miles, and more like 20 miles for most folks, for full marathon training. While that’s certainly helpful for a half, you can easily cap the long run at around 15 miles (if not less) and get pretty good performance. And for half marathons run under about 2:00, you’ll want to throw in more time at Z3 than most “first-time” marathon plans will have – say, one tempo run a week where you warm up for 1-2 miles and then spend 20-30 minutes in Z3.
I’m a big fan of UA training, but for a first-timer running a road half-marathon you might be better served by seeking out another resource. My advice is Daniels Running Formula, 3rd edition.
