Stephen:
Please modify you signature and tell us where you are. I do not know where empire is. For starters, you must be further south than me because my water is about 7-9 degrees colder during the day (maybe not the surface) as this is coming from the heater. I turn on to see how cold the water is. You could be north as well.
Closing a pool over 60 degrees does not necessarily place you in the danger zone. A lot depends on the weather over the next few weeks, and possibly longer. Most of this has to do with the cover you have on the pool. A solid safety cover or tarp is best for sunlight, but does not allow water to seep through. A mesh cover allows water and snow, but can also let sunlight in. If you have another month of sunlight, then you could run into problems.
Your goal is to stall algae until the spring. Neither chlorine nor algaecide will last until the first holiday weekend. If you want to close without algaecide, make sure the pool is perfectly clear, bring the pool to SLAM levels, and then close the pool. If you want to use Poly60, your levels must come down to the normal CYA/FC levels as chlorine will consume the Poly60. Although, I believe the effectiveness is still there, but not by that much. For me, the science behind this is too much to understand, so it is easier for me to follow protocol and leave levels lower.
Please keep us a little more information (City, what type of cover, levels, etc.). Thanks!