Can you show a screen capture of your outdoor map level.
Let us know which version of FPSC you are running and what type of graphics card you have. There are things you can do to make your outside scene a success, just want to see what you have already.
As far as realistic sunlight. Place one light with a range of 2500 or better on level 16 or above and place the light so you get the shadows you want. Set the light color to 200,200,15 and then adjust the Saturation to get your final brightness preference.
BTW the color is just a sugestion, You can use more orange for morning and mor red for dusk, Less saturation for cloudy days and so fourth.
Hope this help some.