I planned it that way. I really wanted to do 20 miles but I knew it was impossible to do it all at once. Running in subzero F temperatures is very hard on my body but also mentally a huge hump I have to get over everyday. I read up on splitting up the long run and decided to do it. I don't think it's ideal but under my circumstances it is the best choice. To get the best effect on running on tired legs I also ran 9 miles Saturday late afternoon. Hopefully that will give me the results that are most similar to a 20 mile long run.
I started in the dark at 6 am. It was -26C/-15F. I stayed in town so the wind wouldn't bother me that much. In the afternoon it luckily had warmed up some, I guess about -20C/0F or so. The final 8 miles actually felt good. I feel good about it. I'm curious where this winter outside training will leave me comes spring. Will I have kept my fitness? Improved? Got super slow? (my fear to be honest) who knows. I do have to tell myself it's a nice test and certainly makes me feel a lot better than logging the miles on the treadmill.
One of the reasons that I don't like to go out of town in the dark ^ apparently these whiskered friends seem to be around quite a bit. I am easily spooked!