When taking in weather as a factor of my fuel required, how does one fit it into the equation?Thanks

It factors into the planning equation immediately based on the wx conditions at your departure airport and the outlook forecast at your arrival time over destination.Are there any wx conditions the may make it impossible for you to land at your destination?What are your forecast ceiling and visibilities at the time of your arrival?Will you need an alternate and if so where is it, what type of approaches does it have and what