If the weather forecast is correct and given how well you are running right now I think you could go well here. Obviously things need to go well to run a good half marathon time, but I do think a PB isn’t impossible. I’ve not set that as a target as I know this isn’t a goal race. But I’ve mentioned it purely to let you know the confidence I have in you right now. No real pressure though, just see what happens. Start off around 9:30 pace and see how you feel as the race progresses. Good luck Jo.