Although some sunshine should reappear this afternoon, another upper level disturbance is expected to return cloud cover to most of Middle TN overnight tonight. A few showers are also possible from Nashville southward.
The clouds should be prevalent everywhere but possibly near the KY border where some patchy frost is possible. The rest of us who are under the cloud cover will not see frost.
Clear skies allow the earth to radiate its heat out into space overnight. That's why it's called "radiational cooling".
On the other hand, clouds reflect the heat (infra-red energy) back towards earth, not allowing the temperature to fall as much, preventing frost.
Tonight there will be a fine line of clouds versus clear to the north, so if you are in towns like Paris, Dover, Clarksville, Springfield, Lafayette, or Celina and you have some late season flowers or vegetables, you may want to cover them up tonight.
I should also note that Monday night (Tuesday morning) should be clear in all of Middle TN, and some patchy frost is possible in many outlying areas, especially north and east of Nashville then.