That is quite an unseasonably cool airmass still being projected on the models. Not taking any airmass modification into account, I think there is great validity for such potential. But before getting into that, when you look at the source region for that airmass there might not be much room for modification.
While this airmass would certainly result in very comfortable daytime temperatures, should we achieve strong mixing (which would be likely with a steep lapse rate), we'll get to at least climo with maybe some areas a tick or two below.
But like you said...it's the overnight period which could be of greatest interest. Given the presence of very dry air and rather low (for time of year) theta-e values, combined with some potential for strong radiative cooling....the favored cold spots could certainly plunge down into the mid-30's and even some of the major climo stations could get into the 40's.
Should any full de-coupling occur profiles are favorable for a downward spiral from daytime high's.