Try this The get weather forecast (daily) returns a list where the first item is the current day, 2nd is tomorrow, 3rd is the day after etc. So when you get weather forecast (daily) you can then use choose item from list to get the forecast for a specified date.
https://www.reddit.com/r/shortcuts/comments/9u7eil/how_to_get_weather_for_tomorrow_with_the_weather/

