I found this on a norwegian hiking page, and this formula is in celcius and millimeters, but I'm sure you will easily convert it into inches and fahrenheit. Anyways, here it goes:
Frozen, clear (without snow) fresh water ice, the thickness grows 2.4 millimeters (~1/10 inch) per day per degree below 0C.
So, if it is a steady 14F (-10C) for a whole day, the ice would be 1 inch thicker during that period, if the ice is cleared of snow.
I haven't verified it, but it should at least give you a guideline.